xref: /titanic_53/usr/src/uts/sun4v/io/vdc.c (revision 6567eb0a4e2af187c63b67198ed307f67a4394f3)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

/*
 * LDoms virtual disk client (vdc) device driver
 *
 * This driver runs on a guest logical domain and communicates with the virtual
 * disk server (vds) driver running on the service domain which is exporting
 * virtualized "disks" to the guest logical domain.
 *
 * The driver can be divided into four sections:
 *
 * 1) generic device driver housekeeping
 *	_init, _fini, attach, detach, ops structures, etc.
 *
 * 2) communication channel setup
 *	Setup the communications link over the LDC channel that vdc uses to
 *	talk to the vDisk server. Initialise the descriptor ring which
 *	allows the LDC clients to transfer data via memory mappings.
 *
 * 3) Support exported to upper layers (filesystems, etc)
 *	The upper layers call into vdc via strategy(9E) and DKIO(7I)
 *	ioctl calls. vdc will copy the data to be written to the descriptor
 *	ring or maps the buffer to store the data read by the vDisk
 *	server into the descriptor ring. It then sends a message to the
 *	vDisk server requesting it to complete the operation.
 *
 * 4) Handling responses from vDisk server.
 *	The vDisk server will ACK some or all of the messages vdc sends to it
 *	(this is configured during the handshake). Upon receipt of an ACK
 *	vdc will check the descriptor ring and signal to the upper layer
 *	code waiting on the IO.
 */

#include <sys/atomic.h>
#include <sys/conf.h>
#include <sys/disp.h>
#include <sys/ddi.h>
#include <sys/dkio.h>
#include <sys/efi_partition.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/mach_descrip.h>
#include <sys/modctl.h>
#include <sys/mdeg.h>
#include <sys/note.h>
#include <sys/open.h>
#include <sys/sdt.h>
#include <sys/stat.h>
#include <sys/sunddi.h>
#include <sys/types.h>
#include <sys/promif.h>
#include <sys/vtoc.h>
#include <sys/archsystm.h>
#include <sys/sysmacros.h>

#include <sys/cdio.h>
#include <sys/dktp/fdisk.h>
#include <sys/scsi/generic/sense.h>
#include <sys/scsi/impl/uscsi.h>	/* Needed for defn of USCSICMD ioctl */

#include <sys/ldoms.h>
#include <sys/ldc.h>
#include <sys/vio_common.h>
#include <sys/vio_mailbox.h>
#include <sys/vdsk_common.h>
#include <sys/vdsk_mailbox.h>
#include <sys/vdc.h>

/*
 * function prototypes
 */

/* standard driver functions */
static int	vdc_open(dev_t *dev, int flag, int otyp, cred_t *cred);
static int	vdc_close(dev_t dev, int flag, int otyp, cred_t *cred);
static int	vdc_strategy(struct buf *buf);
static int	vdc_print(dev_t dev, char *str);
static int	vdc_dump(dev_t dev, caddr_t addr, daddr_t blkno, int nblk);
static int	vdc_read(dev_t dev, struct uio *uio, cred_t *cred);
static int	vdc_write(dev_t dev, struct uio *uio, cred_t *cred);
static int	vdc_ioctl(dev_t dev, int cmd, intptr_t arg, int mode,
			cred_t *credp, int *rvalp);
static int	vdc_aread(dev_t dev, struct aio_req *aio, cred_t *cred);
static int	vdc_awrite(dev_t dev, struct aio_req *aio, cred_t *cred);

static int	vdc_getinfo(dev_info_t *dip, ddi_info_cmd_t cmd,
			void *arg, void **resultp);
static int	vdc_attach(dev_info_t *dip, ddi_attach_cmd_t cmd);
static int	vdc_detach(dev_info_t *dip, ddi_detach_cmd_t cmd);

/* setup */
static void	vdc_min(struct buf *bufp);
static int	vdc_send(vdc_t *vdc, caddr_t pkt, size_t *msglen);
static int	vdc_do_ldc_init(vdc_t *vdc);
static int	vdc_start_ldc_connection(vdc_t *vdc);
static int	vdc_create_device_nodes(vdc_t *vdc);
static int	vdc_create_device_nodes_efi(vdc_t *vdc);
static int	vdc_create_device_nodes_vtoc(vdc_t *vdc);
static int	vdc_create_device_nodes_props(vdc_t *vdc);
static int	vdc_get_ldc_id(dev_info_t *dip, uint64_t *ldc_id);
static int	vdc_do_ldc_up(vdc_t *vdc);
static void	vdc_terminate_ldc(vdc_t *vdc);
static int	vdc_init_descriptor_ring(vdc_t *vdc);
static void	vdc_destroy_descriptor_ring(vdc_t *vdc);
static int	vdc_setup_devid(vdc_t *vdc);
static void	vdc_store_efi(vdc_t *vdc, struct dk_gpt *efi);

/* handshake with vds */
static int		vdc_init_ver_negotiation(vdc_t *vdc, vio_ver_t ver);
static int		vdc_ver_negotiation(vdc_t *vdcp);
static int		vdc_init_attr_negotiation(vdc_t *vdc);
static int		vdc_attr_negotiation(vdc_t *vdcp);
static int		vdc_init_dring_negotiate(vdc_t *vdc);
static int		vdc_dring_negotiation(vdc_t *vdcp);
static int		vdc_send_rdx(vdc_t *vdcp);
static int		vdc_rdx_exchange(vdc_t *vdcp);
static boolean_t	vdc_is_supported_version(vio_ver_msg_t *ver_msg);

/* processing incoming messages from vDisk server */
static void	vdc_process_msg_thread(vdc_t *vdc);
static int	vdc_recv(vdc_t *vdc, vio_msg_t *msgp, size_t *nbytesp);

static uint_t	vdc_handle_cb(uint64_t event, caddr_t arg);
static int	vdc_process_data_msg(vdc_t *vdc, vio_msg_t *msg);
static int	vdc_process_err_msg(vdc_t *vdc, vio_msg_t msg);
static int	vdc_handle_ver_msg(vdc_t *vdc, vio_ver_msg_t *ver_msg);
static int	vdc_handle_attr_msg(vdc_t *vdc, vd_attr_msg_t *attr_msg);
static int	vdc_handle_dring_reg_msg(vdc_t *vdc, vio_dring_reg_msg_t *msg);
static int 	vdc_send_request(vdc_t *vdcp, int operation,
		    caddr_t addr, size_t nbytes, int slice, diskaddr_t offset,
		    int cb_type, void *cb_arg, vio_desc_direction_t dir);
static int	vdc_map_to_shared_dring(vdc_t *vdcp, int idx);
static int 	vdc_populate_descriptor(vdc_t *vdcp, int operation,
		    caddr_t addr, size_t nbytes, int slice, diskaddr_t offset,
		    int cb_type, void *cb_arg, vio_desc_direction_t dir);
static int 	vdc_do_sync_op(vdc_t *vdcp, int operation,
		    caddr_t addr, size_t nbytes, int slice, diskaddr_t offset,
		    int cb_type, void *cb_arg, vio_desc_direction_t dir);

static int	vdc_wait_for_response(vdc_t *vdcp, vio_msg_t *msgp);
static int	vdc_drain_response(vdc_t *vdcp);
static int	vdc_depopulate_descriptor(vdc_t *vdc, uint_t idx);
static int	vdc_populate_mem_hdl(vdc_t *vdcp, vdc_local_desc_t *ldep);
static int	vdc_verify_seq_num(vdc_t *vdc, vio_dring_msg_t *dring_msg);

/* dkio */
static int	vd_process_ioctl(dev_t dev, int cmd, caddr_t arg, int mode);
static int	vdc_create_fake_geometry(vdc_t *vdc);
static int	vdc_setup_disk_layout(vdc_t *vdc);
static int	vdc_null_copy_func(vdc_t *vdc, void *from, void *to,
		    int mode, int dir);
static int	vdc_get_wce_convert(vdc_t *vdc, void *from, void *to,
		    int mode, int dir);
static int	vdc_set_wce_convert(vdc_t *vdc, void *from, void *to,
		    int mode, int dir);
static int	vdc_get_vtoc_convert(vdc_t *vdc, void *from, void *to,
		    int mode, int dir);
static int	vdc_set_vtoc_convert(vdc_t *vdc, void *from, void *to,
		    int mode, int dir);
static int	vdc_get_geom_convert(vdc_t *vdc, void *from, void *to,
		    int mode, int dir);
static int	vdc_set_geom_convert(vdc_t *vdc, void *from, void *to,
		    int mode, int dir);
static int	vdc_uscsicmd_convert(vdc_t *vdc, void *from, void *to,
		    int mode, int dir);
static int	vdc_get_efi_convert(vdc_t *vdc, void *from, void *to,
		    int mode, int dir);
static int	vdc_set_efi_convert(vdc_t *vdc, void *from, void *to,
		    int mode, int dir);

/*
 * Module variables
 */

/*
 * Tunable variables to control how long vdc waits before timing out on
 * various operations
 */
static int	vdc_retries = 10;

/* calculated from 'vdc_usec_timeout' during attach */
static uint64_t	vdc_hz_timeout;				/* units: Hz */
static uint64_t	vdc_usec_timeout = 30 * MICROSEC;	/* 30s units: ns */

static uint64_t vdc_hz_min_ldc_delay;
static uint64_t vdc_min_timeout_ldc = 1 * MILLISEC;
static uint64_t vdc_hz_max_ldc_delay;
static uint64_t vdc_max_timeout_ldc = 100 * MILLISEC;

static uint64_t vdc_ldc_read_init_delay = 1 * MILLISEC;
static uint64_t vdc_ldc_read_max_delay = 100 * MILLISEC;

/* values for dumping - need to run in a tighter loop */
static uint64_t	vdc_usec_timeout_dump = 100 * MILLISEC;	/* 0.1s units: ns */
static int	vdc_dump_retries = 100;

/* Count of the number of vdc instances attached */
static volatile uint32_t	vdc_instance_count = 0;

/* Soft state pointer */
static void	*vdc_state;

/*
 * Controlling the verbosity of the error/debug messages
 *
 * vdc_msglevel - controls level of messages
 * vdc_matchinst - 64-bit variable where each bit corresponds
 *                 to the vdc instance the vdc_msglevel applies.
 */
int		vdc_msglevel = 0x0;
uint64_t	vdc_matchinst = 0ull;

/*
 * Supported vDisk protocol version pairs.
 *
 * The first array entry is the latest and preferred version.
 */
static const vio_ver_t	vdc_version[] = {{1, 0}};

static struct cb_ops vdc_cb_ops = {
	vdc_open,	/* cb_open */
	vdc_close,	/* cb_close */
	vdc_strategy,	/* cb_strategy */
	vdc_print,	/* cb_print */
	vdc_dump,	/* cb_dump */
	vdc_read,	/* cb_read */
	vdc_write,	/* cb_write */
	vdc_ioctl,	/* cb_ioctl */
	nodev,		/* cb_devmap */
	nodev,		/* cb_mmap */
	nodev,		/* cb_segmap */
	nochpoll,	/* cb_chpoll */
	ddi_prop_op,	/* cb_prop_op */
	NULL,		/* cb_str */
	D_MP | D_64BIT,	/* cb_flag */
	CB_REV,		/* cb_rev */
	vdc_aread,	/* cb_aread */
	vdc_awrite	/* cb_awrite */
};

static struct dev_ops vdc_ops = {
	DEVO_REV,	/* devo_rev */
	0,		/* devo_refcnt */
	vdc_getinfo,	/* devo_getinfo */
	nulldev,	/* devo_identify */
	nulldev,	/* devo_probe */
	vdc_attach,	/* devo_attach */
	vdc_detach,	/* devo_detach */
	nodev,		/* devo_reset */
	&vdc_cb_ops,	/* devo_cb_ops */
	NULL,		/* devo_bus_ops */
	nulldev		/* devo_power */
};

static struct modldrv modldrv = {
	&mod_driverops,
	"virtual disk client %I%",
	&vdc_ops,
};

static struct modlinkage modlinkage = {
	MODREV_1,
	&modldrv,
	NULL
};

/* -------------------------------------------------------------------------- */

/*
 * Device Driver housekeeping and setup
 */

int
_init(void)
{
	int	status;

	if ((status = ddi_soft_state_init(&vdc_state, sizeof (vdc_t), 1)) != 0)
		return (status);
	if ((status = mod_install(&modlinkage)) != 0)
		ddi_soft_state_fini(&vdc_state);
	vdc_efi_init(vd_process_ioctl);
	return (status);
}

int
_info(struct modinfo *modinfop)
{
	return (mod_info(&modlinkage, modinfop));
}

int
_fini(void)
{
	int	status;

	if ((status = mod_remove(&modlinkage)) != 0)
		return (status);
	vdc_efi_fini();
	ddi_soft_state_fini(&vdc_state);
	return (0);
}

static int
vdc_getinfo(dev_info_t *dip, ddi_info_cmd_t cmd,  void *arg, void **resultp)
{
	_NOTE(ARGUNUSED(dip))

	int	instance = VDCUNIT((dev_t)arg);
	vdc_t	*vdc = NULL;

	switch (cmd) {
	case DDI_INFO_DEVT2DEVINFO:
		if ((vdc = ddi_get_soft_state(vdc_state, instance)) == NULL) {
			*resultp = NULL;
			return (DDI_FAILURE);
		}
		*resultp = vdc->dip;
		return (DDI_SUCCESS);
	case DDI_INFO_DEVT2INSTANCE:
		*resultp = (void *)(uintptr_t)instance;
		return (DDI_SUCCESS);
	default:
		*resultp = NULL;
		return (DDI_FAILURE);
	}
}

static int
vdc_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
	int	instance;
	int	rv;
	vdc_t	*vdc = NULL;

	switch (cmd) {
	case DDI_DETACH:
		/* the real work happens below */
		break;
	case DDI_SUSPEND:
		/* nothing to do for this non-device */
		return (DDI_SUCCESS);
	default:
		return (DDI_FAILURE);
	}

	ASSERT(cmd == DDI_DETACH);
	instance = ddi_get_instance(dip);
	DMSGX(1, "[%d] Entered\n", instance);

	if ((vdc = ddi_get_soft_state(vdc_state, instance)) == NULL) {
		cmn_err(CE_NOTE, "[%d] Couldn't get state structure", instance);
		return (DDI_FAILURE);
	}

	if (vdc->open_count) {
		DMSG(vdc, 0, "[%d] Cannot detach: device is open", instance);
		return (DDI_FAILURE);
	}

	DMSG(vdc, 0, "[%d] proceeding...\n", instance);

	/* mark instance as detaching */
	vdc->lifecycle	= VDC_LC_DETACHING;

	/*
	 * try and disable callbacks to prevent another handshake
	 */
	rv = ldc_set_cb_mode(vdc->ldc_handle, LDC_CB_DISABLE);
	DMSG(vdc, 0, "callback disabled (rv=%d)\n", rv);

	if (vdc->initialized & VDC_THREAD) {
		mutex_enter(&vdc->read_lock);
		if ((vdc->read_state == VDC_READ_WAITING) ||
		    (vdc->read_state == VDC_READ_RESET)) {
			vdc->read_state = VDC_READ_RESET;
			cv_signal(&vdc->read_cv);
		}

		mutex_exit(&vdc->read_lock);

		/* wake up any thread waiting for connection to come online */
		mutex_enter(&vdc->lock);
		if (vdc->state == VDC_STATE_INIT_WAITING) {
			DMSG(vdc, 0,
			    "[%d] write reset - move to resetting state...\n",
			    instance);
			vdc->state = VDC_STATE_RESETTING;
			cv_signal(&vdc->initwait_cv);
		}
		mutex_exit(&vdc->lock);

		/* now wait until state transitions to VDC_STATE_DETACH */
		thread_join(vdc->msg_proc_thr->t_did);
		ASSERT(vdc->state == VDC_STATE_DETACH);
		DMSG(vdc, 0, "[%d] Reset thread exit and join ..\n",
		    vdc->instance);
	}

	mutex_enter(&vdc->lock);

	if (vdc->initialized & VDC_DRING)
		vdc_destroy_descriptor_ring(vdc);

	if (vdc->initialized & VDC_LDC)
		vdc_terminate_ldc(vdc);

	mutex_exit(&vdc->lock);

	if (vdc->initialized & VDC_MINOR) {
		ddi_prop_remove_all(dip);
		ddi_remove_minor_node(dip, NULL);
	}

	if (vdc->initialized & VDC_LOCKS) {
		mutex_destroy(&vdc->lock);
		mutex_destroy(&vdc->read_lock);
		cv_destroy(&vdc->initwait_cv);
		cv_destroy(&vdc->dring_free_cv);
		cv_destroy(&vdc->membind_cv);
		cv_destroy(&vdc->sync_pending_cv);
		cv_destroy(&vdc->sync_blocked_cv);
		cv_destroy(&vdc->read_cv);
		cv_destroy(&vdc->running_cv);
	}

	if (vdc->minfo)
		kmem_free(vdc->minfo, sizeof (struct dk_minfo));

	if (vdc->cinfo)
		kmem_free(vdc->cinfo, sizeof (struct dk_cinfo));

	if (vdc->vtoc)
		kmem_free(vdc->vtoc, sizeof (struct vtoc));

	if (vdc->label)
		kmem_free(vdc->label, DK_LABEL_SIZE);

	if (vdc->devid) {
		ddi_devid_unregister(dip);
		ddi_devid_free(vdc->devid);
	}

	if (vdc->initialized & VDC_SOFT_STATE)
		ddi_soft_state_free(vdc_state, instance);

	DMSG(vdc, 0, "[%d] End %p\n", instance, (void *)vdc);

	return (DDI_SUCCESS);
}


static int
vdc_do_attach(dev_info_t *dip)
{
	int		instance;
	vdc_t		*vdc = NULL;
	int		status;

	ASSERT(dip != NULL);

	instance = ddi_get_instance(dip);
	if (ddi_soft_state_zalloc(vdc_state, instance) != DDI_SUCCESS) {
		cmn_err(CE_NOTE, "[%d] Couldn't alloc state structure",
		    instance);
		return (DDI_FAILURE);
	}

	if ((vdc = ddi_get_soft_state(vdc_state, instance)) == NULL) {
		cmn_err(CE_NOTE, "[%d] Couldn't get state structure", instance);
		return (DDI_FAILURE);
	}

	/*
	 * We assign the value to initialized in this case to zero out the
	 * variable and then set bits in it to indicate what has been done
	 */
	vdc->initialized = VDC_SOFT_STATE;

	vdc_hz_timeout = drv_usectohz(vdc_usec_timeout);

	vdc_hz_min_ldc_delay = drv_usectohz(vdc_min_timeout_ldc);
	vdc_hz_max_ldc_delay = drv_usectohz(vdc_max_timeout_ldc);

	vdc->dip	= dip;
	vdc->instance	= instance;
	vdc->open_count	= 0;
	vdc->vdisk_type	= VD_DISK_TYPE_UNK;
	vdc->vdisk_label = VD_DISK_LABEL_UNK;
	vdc->state	= VDC_STATE_INIT;
	vdc->lifecycle	= VDC_LC_ATTACHING;
	vdc->ldc_state	= 0;
	vdc->session_id = 0;
	vdc->block_size = DEV_BSIZE;
	vdc->max_xfer_sz = maxphys / DEV_BSIZE;

	vdc->vtoc = NULL;
	vdc->cinfo = NULL;
	vdc->minfo = NULL;

	mutex_init(&vdc->lock, NULL, MUTEX_DRIVER, NULL);
	cv_init(&vdc->initwait_cv, NULL, CV_DRIVER, NULL);
	cv_init(&vdc->dring_free_cv, NULL, CV_DRIVER, NULL);
	cv_init(&vdc->membind_cv, NULL, CV_DRIVER, NULL);
	cv_init(&vdc->running_cv, NULL, CV_DRIVER, NULL);

	vdc->threads_pending = 0;
	vdc->sync_op_pending = B_FALSE;
	vdc->sync_op_blocked = B_FALSE;
	cv_init(&vdc->sync_pending_cv, NULL, CV_DRIVER, NULL);
	cv_init(&vdc->sync_blocked_cv, NULL, CV_DRIVER, NULL);

	/* init blocking msg read functionality */
	mutex_init(&vdc->read_lock, NULL, MUTEX_DRIVER, NULL);
	cv_init(&vdc->read_cv, NULL, CV_DRIVER, NULL);
	vdc->read_state = VDC_READ_IDLE;

	vdc->initialized |= VDC_LOCKS;

	/* initialise LDC channel which will be used to communicate with vds */
	if ((status = vdc_do_ldc_init(vdc)) != 0) {
		cmn_err(CE_NOTE, "[%d] Couldn't initialize LDC", instance);
		goto return_status;
	}

	/* initialize the thread responsible for managing state with server */
	vdc->msg_proc_thr = thread_create(NULL, 0, vdc_process_msg_thread,
	    vdc, 0, &p0, TS_RUN, minclsyspri);
	if (vdc->msg_proc_thr == NULL) {
		cmn_err(CE_NOTE, "[%d] Failed to create msg processing thread",
		    instance);
		return (DDI_FAILURE);
	}

	vdc->initialized |= VDC_THREAD;

	atomic_inc_32(&vdc_instance_count);

	/*
	 * Once the handshake is complete, we can use the DRing to send
	 * requests to the vDisk server to calculate the geometry and
	 * VTOC of the "disk"
	 */
	status = vdc_setup_disk_layout(vdc);
	if (status != 0) {
		DMSG(vdc, 0, "[%d] Failed to discover disk layout (err%d)",
			vdc->instance, status);
		goto return_status;
	}

	/*
	 * Now that we have the device info we can create the
	 * device nodes and properties
	 */
	status = vdc_create_device_nodes(vdc);
	if (status) {
		DMSG(vdc, 0, "[%d] Failed to create device nodes",
				instance);
		goto return_status;
	}
	status = vdc_create_device_nodes_props(vdc);
	if (status) {
		DMSG(vdc, 0, "[%d] Failed to create device nodes"
				" properties (%d)", instance, status);
		goto return_status;
	}

	/*
	 * Setup devid
	 */
	if (vdc_setup_devid(vdc)) {
		DMSG(vdc, 0, "[%d] No device id available\n", instance);
	}

	ddi_report_dev(dip);
	vdc->lifecycle	= VDC_LC_ONLINE;
	DMSG(vdc, 0, "[%d] Attach tasks successful\n", instance);

return_status:
	DMSG(vdc, 0, "[%d] Attach completed\n", instance);
	return (status);
}

static int
vdc_attach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
	int	status;

	switch (cmd) {
	case DDI_ATTACH:
		if ((status = vdc_do_attach(dip)) != 0)
			(void) vdc_detach(dip, DDI_DETACH);
		return (status);
	case DDI_RESUME:
		/* nothing to do for this non-device */
		return (DDI_SUCCESS);
	default:
		return (DDI_FAILURE);
	}
}

static int
vdc_do_ldc_init(vdc_t *vdc)
{
	int			status = 0;
	ldc_status_t		ldc_state;
	ldc_attr_t		ldc_attr;
	uint64_t		ldc_id = 0;
	dev_info_t		*dip = NULL;

	ASSERT(vdc != NULL);

	dip = vdc->dip;
	vdc->initialized |= VDC_LDC;

	if ((status = vdc_get_ldc_id(dip, &ldc_id)) != 0) {
		DMSG(vdc, 0, "[%d] Failed to get LDC channel ID property",
				vdc->instance);
		return (EIO);
	}
	vdc->ldc_id = ldc_id;

	ldc_attr.devclass = LDC_DEV_BLK;
	ldc_attr.instance = vdc->instance;
	ldc_attr.mode = LDC_MODE_UNRELIABLE;	/* unreliable transport */
	ldc_attr.mtu = VD_LDC_MTU;

	if ((vdc->initialized & VDC_LDC_INIT) == 0) {
		status = ldc_init(ldc_id, &ldc_attr, &vdc->ldc_handle);
		if (status != 0) {
			DMSG(vdc, 0, "[%d] ldc_init(chan %ld) returned %d",
					vdc->instance, ldc_id, status);
			return (status);
		}
		vdc->initialized |= VDC_LDC_INIT;
	}
	status = ldc_status(vdc->ldc_handle, &ldc_state);
	if (status != 0) {
		DMSG(vdc, 0, "[%d] Cannot discover LDC status [err=%d]",
				vdc->instance, status);
		return (status);
	}
	vdc->ldc_state = ldc_state;

	if ((vdc->initialized & VDC_LDC_CB) == 0) {
		status = ldc_reg_callback(vdc->ldc_handle, vdc_handle_cb,
		    (caddr_t)vdc);
		if (status != 0) {
			DMSG(vdc, 0, "[%d] LDC callback reg. failed (%d)",
					vdc->instance, status);
			return (status);
		}
		vdc->initialized |= VDC_LDC_CB;
	}

	vdc->initialized |= VDC_LDC;

	/*
	 * At this stage we have initialised LDC, we will now try and open
	 * the connection.
	 */
	if (vdc->ldc_state == LDC_INIT) {
		status = ldc_open(vdc->ldc_handle);
		if (status != 0) {
			DMSG(vdc, 0, "[%d] ldc_open(chan %ld) returned %d",
					vdc->instance, vdc->ldc_id, status);
			return (status);
		}
		vdc->initialized |= VDC_LDC_OPEN;
	}

	return (status);
}

static int
vdc_start_ldc_connection(vdc_t *vdc)
{
	int		status = 0;

	ASSERT(vdc != NULL);

	ASSERT(MUTEX_HELD(&vdc->lock));

	status = vdc_do_ldc_up(vdc);

	DMSG(vdc, 0, "[%d] Finished bringing up LDC\n", vdc->instance);

	return (status);
}

static int
vdc_stop_ldc_connection(vdc_t *vdcp)
{
	int	status;

	DMSG(vdcp, 0, ": Resetting connection to vDisk server : state %d\n",
		vdcp->state);

	status = ldc_down(vdcp->ldc_handle);
	DMSG(vdcp, 0, "ldc_down() = %d\n", status);

	vdcp->initialized &= ~VDC_HANDSHAKE;
	DMSG(vdcp, 0, "initialized=%x\n", vdcp->initialized);

	return (status);
}

static int
vdc_create_device_nodes_efi(vdc_t *vdc)
{
	ddi_remove_minor_node(vdc->dip, "h");
	ddi_remove_minor_node(vdc->dip, "h,raw");

	if (ddi_create_minor_node(vdc->dip, "wd", S_IFBLK,
		VD_MAKE_DEV(vdc->instance, VD_EFI_WD_SLICE),
		DDI_NT_BLOCK, 0) != DDI_SUCCESS) {
		cmn_err(CE_NOTE, "[%d] Couldn't add block node 'wd'",
		    vdc->instance);
		return (EIO);
	}

	/* if any device node is created we set this flag */
	vdc->initialized |= VDC_MINOR;

	if (ddi_create_minor_node(vdc->dip, "wd,raw", S_IFCHR,
		VD_MAKE_DEV(vdc->instance, VD_EFI_WD_SLICE),
		DDI_NT_BLOCK, 0) != DDI_SUCCESS) {
		cmn_err(CE_NOTE, "[%d] Couldn't add block node 'wd,raw'",
		    vdc->instance);
		return (EIO);
	}

	return (0);
}

static int
vdc_create_device_nodes_vtoc(vdc_t *vdc)
{
	ddi_remove_minor_node(vdc->dip, "wd");
	ddi_remove_minor_node(vdc->dip, "wd,raw");

	if (ddi_create_minor_node(vdc->dip, "h", S_IFBLK,
		VD_MAKE_DEV(vdc->instance, VD_EFI_WD_SLICE),
		DDI_NT_BLOCK, 0) != DDI_SUCCESS) {
		cmn_err(CE_NOTE, "[%d] Couldn't add block node 'h'",
		    vdc->instance);
		return (EIO);
	}

	/* if any device node is created we set this flag */
	vdc->initialized |= VDC_MINOR;

	if (ddi_create_minor_node(vdc->dip, "h,raw", S_IFCHR,
		VD_MAKE_DEV(vdc->instance, VD_EFI_WD_SLICE),
		DDI_NT_BLOCK, 0) != DDI_SUCCESS) {
		cmn_err(CE_NOTE, "[%d] Couldn't add block node 'h,raw'",
		    vdc->instance);
		return (EIO);
	}

	return (0);
}

/*
 * Function:
 *	vdc_create_device_nodes
 *
 * Description:
 *	This function creates the block and character device nodes under
 *	/devices along with the node properties. It is called as part of
 *	the attach(9E) of the instance during the handshake with vds after
 *	vds has sent the attributes to vdc.
 *
 *	If the device is of type VD_DISK_TYPE_SLICE then the minor node
 *	of 2 is used in keeping with the Solaris convention that slice 2
 *	refers to a whole disk. Slices start at 'a'
 *
 * Parameters:
 *	vdc 		- soft state pointer
 *
 * Return Values
 *	0		- Success
 *	EIO		- Failed to create node
 *	EINVAL		- Unknown type of disk exported
 */
static int
vdc_create_device_nodes(vdc_t *vdc)
{
	char		name[sizeof ("s,raw")];
	dev_info_t	*dip = NULL;
	int		instance, status;
	int		num_slices = 1;
	int		i;

	ASSERT(vdc != NULL);

	instance = vdc->instance;
	dip = vdc->dip;

	switch (vdc->vdisk_type) {
	case VD_DISK_TYPE_DISK:
		num_slices = V_NUMPAR;
		break;
	case VD_DISK_TYPE_SLICE:
		num_slices = 1;
		break;
	case VD_DISK_TYPE_UNK:
	default:
		return (EINVAL);
	}

	/*
	 * Minor nodes are different for EFI disks: EFI disks do not have
	 * a minor node 'g' for the minor number corresponding to slice
	 * VD_EFI_WD_SLICE (slice 7) instead they have a minor node 'wd'
	 * representing the whole disk.
	 */
	for (i = 0; i < num_slices; i++) {

		if (i == VD_EFI_WD_SLICE) {
			if (vdc->vdisk_label == VD_DISK_LABEL_EFI)
				status = vdc_create_device_nodes_efi(vdc);
			else
				status = vdc_create_device_nodes_vtoc(vdc);
			if (status != 0)
				return (status);
			continue;
		}

		(void) snprintf(name, sizeof (name), "%c", 'a' + i);
		if (ddi_create_minor_node(dip, name, S_IFBLK,
		    VD_MAKE_DEV(instance, i), DDI_NT_BLOCK, 0) != DDI_SUCCESS) {
			cmn_err(CE_NOTE, "[%d] Couldn't add block node '%s'",
				instance, name);
			return (EIO);
		}

		/* if any device node is created we set this flag */
		vdc->initialized |= VDC_MINOR;

		(void) snprintf(name, sizeof (name), "%c%s",
			'a' + i, ",raw");
		if (ddi_create_minor_node(dip, name, S_IFCHR,
		    VD_MAKE_DEV(instance, i), DDI_NT_BLOCK, 0) != DDI_SUCCESS) {
			cmn_err(CE_NOTE, "[%d] Couldn't add raw node '%s'",
				instance, name);
			return (EIO);
		}
	}

	return (0);
}

/*
 * Function:
 *	vdc_create_device_nodes_props
 *
 * Description:
 *	This function creates the block and character device nodes under
 *	/devices along with the node properties. It is called as part of
 *	the attach(9E) of the instance during the handshake with vds after
 *	vds has sent the attributes to vdc.
 *
 * Parameters:
 *	vdc 		- soft state pointer
 *
 * Return Values
 *	0		- Success
 *	EIO		- Failed to create device node property
 *	EINVAL		- Unknown type of disk exported
 */
static int
vdc_create_device_nodes_props(vdc_t *vdc)
{
	dev_info_t	*dip = NULL;
	int		instance;
	int		num_slices = 1;
	int64_t		size = 0;
	dev_t		dev;
	int		rv;
	int		i;

	ASSERT(vdc != NULL);

	instance = vdc->instance;
	dip = vdc->dip;

	if ((vdc->vtoc == NULL) || (vdc->vtoc->v_sanity != VTOC_SANE)) {
		DMSG(vdc, 0, "![%d] Could not create device node property."
				" No VTOC available", instance);
		return (ENXIO);
	}

	switch (vdc->vdisk_type) {
	case VD_DISK_TYPE_DISK:
		num_slices = V_NUMPAR;
		break;
	case VD_DISK_TYPE_SLICE:
		num_slices = 1;
		break;
	case VD_DISK_TYPE_UNK:
	default:
		return (EINVAL);
	}

	for (i = 0; i < num_slices; i++) {
		dev = makedevice(ddi_driver_major(dip),
			VD_MAKE_DEV(instance, i));

		size = vdc->vtoc->v_part[i].p_size * vdc->vtoc->v_sectorsz;
		DMSG(vdc, 0, "[%d] sz %ld (%ld Mb)  p_size %lx\n",
				instance, size, size / (1024 * 1024),
				vdc->vtoc->v_part[i].p_size);

		rv = ddi_prop_update_int64(dev, dip, VDC_SIZE_PROP_NAME, size);
		if (rv != DDI_PROP_SUCCESS) {
			cmn_err(CE_NOTE, "[%d] Couldn't add '%s' prop of [%ld]",
				instance, VDC_SIZE_PROP_NAME, size);
			return (EIO);
		}

		rv = ddi_prop_update_int64(dev, dip, VDC_NBLOCKS_PROP_NAME,
			lbtodb(size));
		if (rv != DDI_PROP_SUCCESS) {
			cmn_err(CE_NOTE, "[%d] Couldn't add '%s' prop [%llu]",
				instance, VDC_NBLOCKS_PROP_NAME, lbtodb(size));
			return (EIO);
		}
	}

	return (0);
}

static int
vdc_open(dev_t *dev, int flag, int otyp, cred_t *cred)
{
	_NOTE(ARGUNUSED(cred))

	int		instance;
	vdc_t		*vdc;

	ASSERT(dev != NULL);
	instance = VDCUNIT(*dev);

	if ((otyp != OTYP_CHR) && (otyp != OTYP_BLK))
		return (EINVAL);

	if ((vdc = ddi_get_soft_state(vdc_state, instance)) == NULL) {
		cmn_err(CE_NOTE, "[%d] Couldn't get state structure", instance);
		return (ENXIO);
	}

	DMSG(vdc, 0, "minor = %d flag = %x, otyp = %x\n",
			getminor(*dev), flag, otyp);

	mutex_enter(&vdc->lock);
	vdc->open_count++;
	mutex_exit(&vdc->lock);

	return (0);
}

static int
vdc_close(dev_t dev, int flag, int otyp, cred_t *cred)
{
	_NOTE(ARGUNUSED(cred))

	int	instance;
	vdc_t	*vdc;

	instance = VDCUNIT(dev);

	if ((otyp != OTYP_CHR) && (otyp != OTYP_BLK))
		return (EINVAL);

	if ((vdc = ddi_get_soft_state(vdc_state, instance)) == NULL) {
		cmn_err(CE_NOTE, "[%d] Couldn't get state structure", instance);
		return (ENXIO);
	}

	DMSG(vdc, 0, "[%d] flag = %x, otyp = %x\n", instance, flag, otyp);
	if (vdc->dkio_flush_pending) {
		DMSG(vdc, 0,
		    "[%d] Cannot detach: %d outstanding DKIO flushes\n",
		    instance, vdc->dkio_flush_pending);
		return (EBUSY);
	}

	/*
	 * Should not need the mutex here, since the framework should protect
	 * against more opens on this device, but just in case.
	 */
	mutex_enter(&vdc->lock);
	vdc->open_count--;
	mutex_exit(&vdc->lock);

	return (0);
}

static int
vdc_ioctl(dev_t dev, int cmd, intptr_t arg, int mode, cred_t *credp, int *rvalp)
{
	_NOTE(ARGUNUSED(credp))
	_NOTE(ARGUNUSED(rvalp))

	return (vd_process_ioctl(dev, cmd, (caddr_t)arg, mode));
}

static int
vdc_print(dev_t dev, char *str)
{
	cmn_err(CE_NOTE, "vdc%d:  %s", VDCUNIT(dev), str);
	return (0);
}

static int
vdc_dump(dev_t dev, caddr_t addr, daddr_t blkno, int nblk)
{
	int	rv;
	size_t	nbytes = nblk * DEV_BSIZE;
	int	instance = VDCUNIT(dev);
	vdc_t	*vdc = NULL;

	if ((vdc = ddi_get_soft_state(vdc_state, instance)) == NULL) {
		cmn_err(CE_NOTE, "[%d] Couldn't get state structure", instance);
		return (ENXIO);
	}

	DMSG(vdc, 2, "[%d] dump %ld bytes at block 0x%lx : addr=0x%p\n",
	    instance, nbytes, blkno, (void *)addr);
	rv = vdc_send_request(vdc, VD_OP_BWRITE, addr, nbytes,
	    VDCPART(dev), blkno, CB_STRATEGY, 0, VIO_write_dir);
	if (rv) {
		DMSG(vdc, 0, "Failed to do a disk dump (err=%d)\n", rv);
		return (rv);
	}

	if (ddi_in_panic())
		(void) vdc_drain_response(vdc);

	DMSG(vdc, 0, "[%d] End\n", instance);

	return (0);
}

/* -------------------------------------------------------------------------- */

/*
 * Disk access routines
 *
 */

/*
 * vdc_strategy()
 *
 * Return Value:
 *	0:	As per strategy(9E), the strategy() function must return 0
 *		[ bioerror(9f) sets b_flags to the proper error code ]
 */
static int
vdc_strategy(struct buf *buf)
{
	int	rv = -1;
	vdc_t	*vdc = NULL;
	int	instance = VDCUNIT(buf->b_edev);
	int	op = (buf->b_flags & B_READ) ? VD_OP_BREAD : VD_OP_BWRITE;

	if ((vdc = ddi_get_soft_state(vdc_state, instance)) == NULL) {
		cmn_err(CE_NOTE, "[%d] Couldn't get state structure", instance);
		bioerror(buf, ENXIO);
		biodone(buf);
		return (0);
	}

	DMSG(vdc, 2, "[%d] %s %ld bytes at block %llx : b_addr=0x%p\n",
	    instance, (buf->b_flags & B_READ) ? "Read" : "Write",
	    buf->b_bcount, buf->b_lblkno, (void *)buf->b_un.b_addr);
	DTRACE_IO2(vstart, buf_t *, buf, vdc_t *, vdc);

	bp_mapin(buf);

	rv = vdc_send_request(vdc, op, (caddr_t)buf->b_un.b_addr,
	    buf->b_bcount, VDCPART(buf->b_edev), buf->b_lblkno,
	    CB_STRATEGY, buf, (op == VD_OP_BREAD) ? VIO_read_dir :
	    VIO_write_dir);

	ASSERT(rv == 0 || rv == EINVAL);

	/*
	 * If the request was successfully sent, the strategy call returns and
	 * the ACK handler calls the bioxxx functions when the vDisk server is
	 * done.
	 */
	if (rv) {
		DMSG(vdc, 0, "Failed to read/write (err=%d)\n", rv);
		bioerror(buf, rv);
		biodone(buf);
	}

	return (0);
}

/*
 * Function:
 *	vdc_min
 *
 * Description:
 *	Routine to limit the size of a data transfer. Used in
 *	conjunction with physio(9F).
 *
 * Arguments:
 *	bp - pointer to the indicated buf(9S) struct.
 *
 */
static void
vdc_min(struct buf *bufp)
{
	vdc_t	*vdc = NULL;
	int	instance = VDCUNIT(bufp->b_edev);

	vdc = ddi_get_soft_state(vdc_state, instance);
	VERIFY(vdc != NULL);

	if (bufp->b_bcount > (vdc->max_xfer_sz * vdc->block_size)) {
		bufp->b_bcount = vdc->max_xfer_sz * vdc->block_size;
	}
}

static int
vdc_read(dev_t dev, struct uio *uio, cred_t *cred)
{
	_NOTE(ARGUNUSED(cred))

	DMSGX(1, "[%d] Entered", VDCUNIT(dev));
	return (physio(vdc_strategy, NULL, dev, B_READ, vdc_min, uio));
}

static int
vdc_write(dev_t dev, struct uio *uio, cred_t *cred)
{
	_NOTE(ARGUNUSED(cred))

	DMSGX(1, "[%d] Entered", VDCUNIT(dev));
	return (physio(vdc_strategy, NULL, dev, B_WRITE, vdc_min, uio));
}

static int
vdc_aread(dev_t dev, struct aio_req *aio, cred_t *cred)
{
	_NOTE(ARGUNUSED(cred))

	DMSGX(1, "[%d] Entered", VDCUNIT(dev));
	return (aphysio(vdc_strategy, anocancel, dev, B_READ, vdc_min, aio));
}

static int
vdc_awrite(dev_t dev, struct aio_req *aio, cred_t *cred)
{
	_NOTE(ARGUNUSED(cred))

	DMSGX(1, "[%d] Entered", VDCUNIT(dev));
	return (aphysio(vdc_strategy, anocancel, dev, B_WRITE, vdc_min, aio));
}


/* -------------------------------------------------------------------------- */

/*
 * Handshake support
 */


/*
 * Function:
 *	vdc_init_ver_negotiation()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_init_ver_negotiation(vdc_t *vdc, vio_ver_t ver)
{
	vio_ver_msg_t	pkt;
	size_t		msglen = sizeof (pkt);
	int		status = -1;

	ASSERT(vdc != NULL);
	ASSERT(mutex_owned(&vdc->lock));

	DMSG(vdc, 0, "[%d] Entered.\n", vdc->instance);

	/*
	 * set the Session ID to a unique value
	 * (the lower 32 bits of the clock tick)
	 */
	vdc->session_id = ((uint32_t)gettick() & 0xffffffff);
	DMSG(vdc, 0, "[%d] Set SID to 0x%lx\n", vdc->instance, vdc->session_id);

	pkt.tag.vio_msgtype = VIO_TYPE_CTRL;
	pkt.tag.vio_subtype = VIO_SUBTYPE_INFO;
	pkt.tag.vio_subtype_env = VIO_VER_INFO;
	pkt.tag.vio_sid = vdc->session_id;
	pkt.dev_class = VDEV_DISK;
	pkt.ver_major = ver.major;
	pkt.ver_minor = ver.minor;

	status = vdc_send(vdc, (caddr_t)&pkt, &msglen);
	DMSG(vdc, 0, "[%d] Ver info sent (status = %d)\n",
	    vdc->instance, status);
	if ((status != 0) || (msglen != sizeof (vio_ver_msg_t))) {
		DMSG(vdc, 0, "[%d] Failed to send Ver negotiation info: "
				"id(%lx) rv(%d) size(%ld)",
				vdc->instance, vdc->ldc_handle,
				status, msglen);
		if (msglen != sizeof (vio_ver_msg_t))
			status = ENOMSG;
	}

	return (status);
}

/*
 * Function:
 *	vdc_ver_negotiation()
 *
 * Description:
 *
 * Arguments:
 *	vdcp	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_ver_negotiation(vdc_t *vdcp)
{
	vio_msg_t vio_msg;
	int status;

	if (status = vdc_init_ver_negotiation(vdcp, vdc_version[0]))
		return (status);

	/* release lock and wait for response */
	mutex_exit(&vdcp->lock);
	status = vdc_wait_for_response(vdcp, &vio_msg);
	mutex_enter(&vdcp->lock);
	if (status) {
		DMSG(vdcp, 0,
		    "[%d] Failed waiting for Ver negotiation response, rv(%d)",
		    vdcp->instance, status);
		return (status);
	}

	/* check type and sub_type ... */
	if (vio_msg.tag.vio_msgtype != VIO_TYPE_CTRL ||
	    vio_msg.tag.vio_subtype == VIO_SUBTYPE_INFO) {
		DMSG(vdcp, 0, "[%d] Invalid ver negotiation response\n",
				vdcp->instance);
		return (EPROTO);
	}

	return (vdc_handle_ver_msg(vdcp, (vio_ver_msg_t *)&vio_msg));
}

/*
 * Function:
 *	vdc_init_attr_negotiation()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_init_attr_negotiation(vdc_t *vdc)
{
	vd_attr_msg_t	pkt;
	size_t		msglen = sizeof (pkt);
	int		status;

	ASSERT(vdc != NULL);
	ASSERT(mutex_owned(&vdc->lock));

	DMSG(vdc, 0, "[%d] entered\n", vdc->instance);

	/* fill in tag */
	pkt.tag.vio_msgtype = VIO_TYPE_CTRL;
	pkt.tag.vio_subtype = VIO_SUBTYPE_INFO;
	pkt.tag.vio_subtype_env = VIO_ATTR_INFO;
	pkt.tag.vio_sid = vdc->session_id;
	/* fill in payload */
	pkt.max_xfer_sz = vdc->max_xfer_sz;
	pkt.vdisk_block_size = vdc->block_size;
	pkt.xfer_mode = VIO_DRING_MODE;
	pkt.operations = 0;	/* server will set bits of valid operations */
	pkt.vdisk_type = 0;	/* server will set to valid device type */
	pkt.vdisk_size = 0;	/* server will set to valid size */

	status = vdc_send(vdc, (caddr_t)&pkt, &msglen);
	DMSG(vdc, 0, "Attr info sent (status = %d)\n", status);

	if ((status != 0) || (msglen != sizeof (vio_ver_msg_t))) {
		DMSG(vdc, 0, "[%d] Failed to send Attr negotiation info: "
				"id(%lx) rv(%d) size(%ld)",
				vdc->instance, vdc->ldc_handle,
				status, msglen);
		if (msglen != sizeof (vio_ver_msg_t))
			status = ENOMSG;
	}

	return (status);
}

/*
 * Function:
 *	vdc_attr_negotiation()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_attr_negotiation(vdc_t *vdcp)
{
	int status;
	vio_msg_t vio_msg;

	if (status = vdc_init_attr_negotiation(vdcp))
		return (status);

	/* release lock and wait for response */
	mutex_exit(&vdcp->lock);
	status = vdc_wait_for_response(vdcp, &vio_msg);
	mutex_enter(&vdcp->lock);
	if (status) {
		DMSG(vdcp, 0,
		    "[%d] Failed waiting for Attr negotiation response, rv(%d)",
		    vdcp->instance, status);
		return (status);
	}

	/* check type and sub_type ... */
	if (vio_msg.tag.vio_msgtype != VIO_TYPE_CTRL ||
	    vio_msg.tag.vio_subtype == VIO_SUBTYPE_INFO) {
		DMSG(vdcp, 0, "[%d] Invalid attr negotiation response\n",
				vdcp->instance);
		return (EPROTO);
	}

	return (vdc_handle_attr_msg(vdcp, (vd_attr_msg_t *)&vio_msg));
}


/*
 * Function:
 *	vdc_init_dring_negotiate()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_init_dring_negotiate(vdc_t *vdc)
{
	vio_dring_reg_msg_t	pkt;
	size_t			msglen = sizeof (pkt);
	int			status = -1;
	int			retry;
	int			nretries = 10;

	ASSERT(vdc != NULL);
	ASSERT(mutex_owned(&vdc->lock));

	for (retry = 0; retry < nretries; retry++) {
		status = vdc_init_descriptor_ring(vdc);
		if (status != EAGAIN)
			break;
		drv_usecwait(vdc_min_timeout_ldc);
	}

	if (status != 0) {
		DMSG(vdc, 0, "[%d] Failed to init DRing (status = %d)\n",
				vdc->instance, status);
		return (status);
	}

	DMSG(vdc, 0, "[%d] Init of descriptor ring completed (status = %d)\n",
			vdc->instance, status);

	/* fill in tag */
	pkt.tag.vio_msgtype = VIO_TYPE_CTRL;
	pkt.tag.vio_subtype = VIO_SUBTYPE_INFO;
	pkt.tag.vio_subtype_env = VIO_DRING_REG;
	pkt.tag.vio_sid = vdc->session_id;
	/* fill in payload */
	pkt.dring_ident = 0;
	pkt.num_descriptors = vdc->dring_len;
	pkt.descriptor_size = vdc->dring_entry_size;
	pkt.options = (VIO_TX_DRING | VIO_RX_DRING);
	pkt.ncookies = vdc->dring_cookie_count;
	pkt.cookie[0] = vdc->dring_cookie[0];	/* for now just one cookie */

	status = vdc_send(vdc, (caddr_t)&pkt, &msglen);
	if (status != 0) {
		DMSG(vdc, 0, "[%d] Failed to register DRing (err = %d)",
				vdc->instance, status);
	}

	return (status);
}


/*
 * Function:
 *	vdc_dring_negotiation()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_dring_negotiation(vdc_t *vdcp)
{
	int status;
	vio_msg_t vio_msg;

	if (status = vdc_init_dring_negotiate(vdcp))
		return (status);

	/* release lock and wait for response */
	mutex_exit(&vdcp->lock);
	status = vdc_wait_for_response(vdcp, &vio_msg);
	mutex_enter(&vdcp->lock);
	if (status) {
		DMSG(vdcp, 0,
		    "[%d] Failed waiting for Dring negotiation response,"
		    " rv(%d)", vdcp->instance, status);
		return (status);
	}

	/* check type and sub_type ... */
	if (vio_msg.tag.vio_msgtype != VIO_TYPE_CTRL ||
	    vio_msg.tag.vio_subtype == VIO_SUBTYPE_INFO) {
		DMSG(vdcp, 0, "[%d] Invalid Dring negotiation response\n",
				vdcp->instance);
		return (EPROTO);
	}

	return (vdc_handle_dring_reg_msg(vdcp,
		    (vio_dring_reg_msg_t *)&vio_msg));
}


/*
 * Function:
 *	vdc_send_rdx()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_send_rdx(vdc_t *vdcp)
{
	vio_msg_t	msg;
	size_t		msglen = sizeof (vio_msg_t);
	int		status;

	/*
	 * Send an RDX message to vds to indicate we are ready
	 * to send data
	 */
	msg.tag.vio_msgtype = VIO_TYPE_CTRL;
	msg.tag.vio_subtype = VIO_SUBTYPE_INFO;
	msg.tag.vio_subtype_env = VIO_RDX;
	msg.tag.vio_sid = vdcp->session_id;
	status = vdc_send(vdcp, (caddr_t)&msg, &msglen);
	if (status != 0) {
		DMSG(vdcp, 0, "[%d] Failed to send RDX message (%d)",
		    vdcp->instance, status);
	}

	return (status);
}

/*
 * Function:
 *	vdc_handle_rdx()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *	msgp	- received msg
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_handle_rdx(vdc_t *vdcp, vio_rdx_msg_t *msgp)
{
	_NOTE(ARGUNUSED(vdcp))
	_NOTE(ARGUNUSED(msgp))

	ASSERT(msgp->tag.vio_msgtype == VIO_TYPE_CTRL);
	ASSERT(msgp->tag.vio_subtype == VIO_SUBTYPE_ACK);
	ASSERT(msgp->tag.vio_subtype_env == VIO_RDX);

	DMSG(vdcp, 1, "[%d] Got an RDX msg", vdcp->instance);

	return (0);
}

/*
 * Function:
 *	vdc_rdx_exchange()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_rdx_exchange(vdc_t *vdcp)
{
	int status;
	vio_msg_t vio_msg;

	if (status = vdc_send_rdx(vdcp))
		return (status);

	/* release lock and wait for response */
	mutex_exit(&vdcp->lock);
	status = vdc_wait_for_response(vdcp, &vio_msg);
	mutex_enter(&vdcp->lock);
	if (status) {
		DMSG(vdcp, 0,
		    "[%d] Failed waiting for RDX response,"
		    " rv(%d)", vdcp->instance, status);
		return (status);
	}

	/* check type and sub_type ... */
	if (vio_msg.tag.vio_msgtype != VIO_TYPE_CTRL ||
	    vio_msg.tag.vio_subtype != VIO_SUBTYPE_ACK) {
		DMSG(vdcp, 0, "[%d] Invalid RDX response\n",
				vdcp->instance);
		return (EPROTO);
	}

	return (vdc_handle_rdx(vdcp, (vio_rdx_msg_t *)&vio_msg));
}


/* -------------------------------------------------------------------------- */

/*
 * LDC helper routines
 */

static int
vdc_recv(vdc_t *vdc, vio_msg_t *msgp, size_t *nbytesp)
{
	int		status;
	boolean_t	q_has_pkts = B_FALSE;
	int		delay_time;
	size_t		len;

	mutex_enter(&vdc->read_lock);

	if (vdc->read_state == VDC_READ_IDLE)
		vdc->read_state = VDC_READ_WAITING;

	while (vdc->read_state != VDC_READ_PENDING) {

		/* detect if the connection has been reset */
		if (vdc->read_state == VDC_READ_RESET) {
			status = ECONNRESET;
			goto done;
		}

		cv_wait(&vdc->read_cv, &vdc->read_lock);
	}

	/*
	 * Until we get a blocking ldc read we have to retry
	 * until the entire LDC message has arrived before
	 * ldc_read() will succeed. Note we also bail out if
	 * the chanel is reset or goes away.
	 */
	delay_time = vdc_ldc_read_init_delay;
loop:
	len = *nbytesp;
	status = ldc_read(vdc->ldc_handle, (caddr_t)msgp, &len);
	switch (status) {
	case EAGAIN:
		delay_time *= 2;
		if (delay_time >= vdc_ldc_read_max_delay)
			delay_time = vdc_ldc_read_max_delay;
		delay(delay_time);
		goto loop;

	case 0:
		if (len == 0) {
			DMSG(vdc, 0, "[%d] ldc_read returned 0 bytes with "
				"no error!\n", vdc->instance);
			goto loop;
		}

		*nbytesp = len;

		/*
		 * If there are pending messages, leave the
		 * read state as pending. Otherwise, set the state
		 * back to idle.
		 */
		status = ldc_chkq(vdc->ldc_handle, &q_has_pkts);
		if (status == 0 && !q_has_pkts)
			vdc->read_state = VDC_READ_IDLE;

		break;
	default:
		DMSG(vdc, 0, "ldc_read returned %d\n", status);
		break;
	}

done:
	mutex_exit(&vdc->read_lock);

	return (status);
}



#ifdef DEBUG
void
vdc_decode_tag(vdc_t *vdcp, vio_msg_t *msg)
{
	char *ms, *ss, *ses;
	switch (msg->tag.vio_msgtype) {
#define	Q(_s)	case _s : ms = #_s; break;
	Q(VIO_TYPE_CTRL)
	Q(VIO_TYPE_DATA)
	Q(VIO_TYPE_ERR)
#undef Q
	default: ms = "unknown"; break;
	}

	switch (msg->tag.vio_subtype) {
#define	Q(_s)	case _s : ss = #_s; break;
	Q(VIO_SUBTYPE_INFO)
	Q(VIO_SUBTYPE_ACK)
	Q(VIO_SUBTYPE_NACK)
#undef Q
	default: ss = "unknown"; break;
	}

	switch (msg->tag.vio_subtype_env) {
#define	Q(_s)	case _s : ses = #_s; break;
	Q(VIO_VER_INFO)
	Q(VIO_ATTR_INFO)
	Q(VIO_DRING_REG)
	Q(VIO_DRING_UNREG)
	Q(VIO_RDX)
	Q(VIO_PKT_DATA)
	Q(VIO_DESC_DATA)
	Q(VIO_DRING_DATA)
#undef Q
	default: ses = "unknown"; break;
	}

	DMSG(vdcp, 3, "(%x/%x/%x) message : (%s/%s/%s)\n",
	    msg->tag.vio_msgtype, msg->tag.vio_subtype,
	    msg->tag.vio_subtype_env, ms, ss, ses);
}
#endif

/*
 * Function:
 *	vdc_send()
 *
 * Description:
 *	The function encapsulates the call to write a message using LDC.
 *	If LDC indicates that the call failed due to the queue being full,
 *	we retry the ldc_write() [ up to 'vdc_retries' time ], otherwise
 *	we return the error returned by LDC.
 *
 * Arguments:
 *	ldc_handle	- LDC handle for the channel this instance of vdc uses
 *	pkt		- address of LDC message to be sent
 *	msglen		- the size of the message being sent. When the function
 *			  returns, this contains the number of bytes written.
 *
 * Return Code:
 *	0		- Success.
 *	EINVAL		- pkt or msglen were NULL
 *	ECONNRESET	- The connection was not up.
 *	EWOULDBLOCK	- LDC queue is full
 *	xxx		- other error codes returned by ldc_write
 */
static int
vdc_send(vdc_t *vdc, caddr_t pkt, size_t *msglen)
{
	size_t	size = 0;
	int	status = 0;
	clock_t delay_ticks;

	ASSERT(vdc != NULL);
	ASSERT(mutex_owned(&vdc->lock));
	ASSERT(msglen != NULL);
	ASSERT(*msglen != 0);

#ifdef DEBUG
	vdc_decode_tag(vdc, (vio_msg_t *)pkt);
#endif
	/*
	 * Wait indefinitely to send if channel
	 * is busy, but bail out if we succeed or
	 * if the channel closes or is reset.
	 */
	delay_ticks = vdc_hz_min_ldc_delay;
	do {
		size = *msglen;
		status = ldc_write(vdc->ldc_handle, pkt, &size);
		if (status == EWOULDBLOCK) {
			delay(delay_ticks);
			/* geometric backoff */
			delay_ticks *= 2;
			if (delay_ticks > vdc_hz_max_ldc_delay)
				delay_ticks = vdc_hz_max_ldc_delay;
		}
	} while (status == EWOULDBLOCK);

	/* if LDC had serious issues --- reset vdc state */
	if (status == EIO || status == ECONNRESET) {
		/* LDC had serious issues --- reset vdc state */
		mutex_enter(&vdc->read_lock);
		if ((vdc->read_state == VDC_READ_WAITING) ||
		    (vdc->read_state == VDC_READ_RESET))
			cv_signal(&vdc->read_cv);
		vdc->read_state = VDC_READ_RESET;
		mutex_exit(&vdc->read_lock);

		/* wake up any waiters in the reset thread */
		if (vdc->state == VDC_STATE_INIT_WAITING) {
			DMSG(vdc, 0, "[%d] write reset - "
			    "vdc is resetting ..\n", vdc->instance);
			vdc->state = VDC_STATE_RESETTING;
			cv_signal(&vdc->initwait_cv);
		}

		return (ECONNRESET);
	}

	/* return the last size written */
	*msglen = size;

	return (status);
}

/*
 * Function:
 *	vdc_get_ldc_id()
 *
 * Description:
 *	This function gets the 'ldc-id' for this particular instance of vdc.
 *	The id returned is the guest domain channel endpoint LDC uses for
 *	communication with vds.
 *
 * Arguments:
 *	dip	- dev info pointer for this instance of the device driver.
 *	ldc_id	- pointer to variable used to return the 'ldc-id' found.
 *
 * Return Code:
 *	0	- Success.
 *	ENOENT	- Expected node or property did not exist.
 *	ENXIO	- Unexpected error communicating with MD framework
 */
static int
vdc_get_ldc_id(dev_info_t *dip, uint64_t *ldc_id)
{
	int		status = ENOENT;
	char		*node_name = NULL;
	md_t		*mdp = NULL;
	int		num_nodes;
	int		num_vdevs;
	int		num_chans;
	mde_cookie_t	rootnode;
	mde_cookie_t	*listp = NULL;
	mde_cookie_t	*chanp = NULL;
	boolean_t	found_inst = B_FALSE;
	int		listsz;
	int		idx;
	uint64_t	md_inst;
	int		obp_inst;
	int		instance = ddi_get_instance(dip);

	ASSERT(ldc_id != NULL);
	*ldc_id = 0;

	/*
	 * Get the OBP instance number for comparison with the MD instance
	 *
	 * The "cfg-handle" property of a vdc node in an MD contains the MD's
	 * notion of "instance", or unique identifier, for that node; OBP
	 * stores the value of the "cfg-handle" MD property as the value of
	 * the "reg" property on the node in the device tree it builds from
	 * the MD and passes to Solaris.  Thus, we look up the devinfo node's
	 * "reg" property value to uniquely identify this device instance.
	 * If the "reg" property cannot be found, the device tree state is
	 * presumably so broken that there is no point in continuing.
	 */
	if (!ddi_prop_exists(DDI_DEV_T_ANY, dip, DDI_PROP_DONTPASS, OBP_REG)) {
		cmn_err(CE_WARN, "'%s' property does not exist", OBP_REG);
		return (ENOENT);
	}
	obp_inst = ddi_prop_get_int(DDI_DEV_T_ANY, dip, DDI_PROP_DONTPASS,
			OBP_REG, -1);
	DMSGX(1, "[%d] OBP inst=%d\n", instance, obp_inst);

	/*
	 * We now walk the MD nodes and if an instance of a vdc node matches
	 * the instance got from OBP we get the ldc-id property.
	 */
	if ((mdp = md_get_handle()) == NULL) {
		cmn_err(CE_WARN, "unable to init machine description");
		return (ENXIO);
	}

	num_nodes = md_node_count(mdp);
	ASSERT(num_nodes > 0);

	listsz = num_nodes * sizeof (mde_cookie_t);

	/* allocate memory for nodes */
	listp = kmem_zalloc(listsz, KM_SLEEP);
	chanp = kmem_zalloc(listsz, KM_SLEEP);

	rootnode = md_root_node(mdp);
	ASSERT(rootnode != MDE_INVAL_ELEM_COOKIE);

	/*
	 * Search for all the virtual devices, we will then check to see which
	 * ones are disk nodes.
	 */
	num_vdevs = md_scan_dag(mdp, rootnode,
			md_find_name(mdp, VDC_MD_VDEV_NAME),
			md_find_name(mdp, "fwd"), listp);

	if (num_vdevs <= 0) {
		cmn_err(CE_NOTE, "No '%s' node found", VDC_MD_VDEV_NAME);
		status = ENOENT;
		goto done;
	}

	DMSGX(1, "[%d] num_vdevs=%d\n", instance, num_vdevs);
	for (idx = 0; idx < num_vdevs; idx++) {
		status = md_get_prop_str(mdp, listp[idx], "name", &node_name);
		if ((status != 0) || (node_name == NULL)) {
			cmn_err(CE_NOTE, "Unable to get name of node type '%s'"
					": err %d", VDC_MD_VDEV_NAME, status);
			continue;
		}

		DMSGX(1, "[%d] Found node '%s'\n", instance, node_name);
		if (strcmp(VDC_MD_DISK_NAME, node_name) == 0) {
			status = md_get_prop_val(mdp, listp[idx],
					VDC_MD_CFG_HDL, &md_inst);
			DMSGX(1, "[%d] vdc inst in MD=%lx\n",
			    instance, md_inst);
			if ((status == 0) && (md_inst == obp_inst)) {
				found_inst = B_TRUE;
				break;
			}
		}
	}

	if (!found_inst) {
		DMSGX(0, "Unable to find correct '%s' node", VDC_MD_DISK_NAME);
		status = ENOENT;
		goto done;
	}
	DMSGX(0, "[%d] MD inst=%lx\n", instance, md_inst);

	/* get the channels for this node */
	num_chans = md_scan_dag(mdp, listp[idx],
			md_find_name(mdp, VDC_MD_CHAN_NAME),
			md_find_name(mdp, "fwd"), chanp);

	/* expecting at least one channel */
	if (num_chans <= 0) {
		cmn_err(CE_NOTE, "No '%s' node for '%s' port",
				VDC_MD_CHAN_NAME, VDC_MD_VDEV_NAME);
		status = ENOENT;
		goto done;

	} else if (num_chans != 1) {
		DMSGX(0, "[%d] Expected 1 '%s' node for '%s' port, found %d\n",
			instance, VDC_MD_CHAN_NAME, VDC_MD_VDEV_NAME,
			num_chans);
	}

	/*
	 * We use the first channel found (index 0), irrespective of how
	 * many are there in total.
	 */
	if (md_get_prop_val(mdp, chanp[0], VDC_ID_PROP, ldc_id) != 0) {
		cmn_err(CE_NOTE, "Channel '%s' property not found",
				VDC_ID_PROP);
		status = ENOENT;
	}

	DMSGX(0, "[%d] LDC id is 0x%lx\n", instance, *ldc_id);

done:
	if (chanp)
		kmem_free(chanp, listsz);
	if (listp)
		kmem_free(listp, listsz);

	(void) md_fini_handle(mdp);

	return (status);
}

static int
vdc_do_ldc_up(vdc_t *vdc)
{
	int		status;
	ldc_status_t	ldc_state;

	DMSG(vdc, 0, "[%d] Bringing up channel %lx\n",
	    vdc->instance, vdc->ldc_id);

	if (vdc->lifecycle == VDC_LC_DETACHING)
		return (EINVAL);

	if ((status = ldc_up(vdc->ldc_handle)) != 0) {
		switch (status) {
		case ECONNREFUSED:	/* listener not ready at other end */
			DMSG(vdc, 0, "[%d] ldc_up(%lx,...) return %d\n",
					vdc->instance, vdc->ldc_id, status);
			status = 0;
			break;
		default:
			DMSG(vdc, 0, "[%d] Failed to bring up LDC: "
			    "channel=%ld, err=%d", vdc->instance, vdc->ldc_id,
			    status);
			break;
		}
	}

	if (ldc_status(vdc->ldc_handle, &ldc_state) == 0) {
		vdc->ldc_state = ldc_state;
		if (ldc_state == LDC_UP) {
			DMSG(vdc, 0, "[%d] LDC channel already up\n",
			    vdc->instance);
			vdc->seq_num = 1;
			vdc->seq_num_reply = 0;
		}
	}

	return (status);
}

/*
 * Function:
 *	vdc_terminate_ldc()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	None
 */
static void
vdc_terminate_ldc(vdc_t *vdc)
{
	int	instance = ddi_get_instance(vdc->dip);

	ASSERT(vdc != NULL);
	ASSERT(mutex_owned(&vdc->lock));

	DMSG(vdc, 0, "[%d] initialized=%x\n", instance, vdc->initialized);

	if (vdc->initialized & VDC_LDC_OPEN) {
		DMSG(vdc, 0, "[%d] ldc_close()\n", instance);
		(void) ldc_close(vdc->ldc_handle);
	}
	if (vdc->initialized & VDC_LDC_CB) {
		DMSG(vdc, 0, "[%d] ldc_unreg_callback()\n", instance);
		(void) ldc_unreg_callback(vdc->ldc_handle);
	}
	if (vdc->initialized & VDC_LDC) {
		DMSG(vdc, 0, "[%d] ldc_fini()\n", instance);
		(void) ldc_fini(vdc->ldc_handle);
		vdc->ldc_handle = NULL;
	}

	vdc->initialized &= ~(VDC_LDC | VDC_LDC_CB | VDC_LDC_OPEN);
}

/* -------------------------------------------------------------------------- */

/*
 * Descriptor Ring helper routines
 */

/*
 * Function:
 *	vdc_init_descriptor_ring()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_init_descriptor_ring(vdc_t *vdc)
{
	vd_dring_entry_t	*dep = NULL;	/* DRing Entry pointer */
	int	status = 0;
	int	i;

	DMSG(vdc, 0, "[%d] initialized=%x\n", vdc->instance, vdc->initialized);

	ASSERT(vdc != NULL);
	ASSERT(mutex_owned(&vdc->lock));
	ASSERT(vdc->ldc_handle != NULL);

	/* ensure we have enough room to store max sized block */
	ASSERT(maxphys <= VD_MAX_BLOCK_SIZE);

	if ((vdc->initialized & VDC_DRING_INIT) == 0) {
		DMSG(vdc, 0, "[%d] ldc_mem_dring_create\n", vdc->instance);
		/*
		 * Calculate the maximum block size we can transmit using one
		 * Descriptor Ring entry from the attributes returned by the
		 * vDisk server. This is subject to a minimum of 'maxphys'
		 * as we do not have the capability to split requests over
		 * multiple DRing entries.
		 */
		if ((vdc->max_xfer_sz * vdc->block_size) < maxphys) {
			DMSG(vdc, 0, "[%d] using minimum DRing size\n",
					vdc->instance);
			vdc->dring_max_cookies = maxphys / PAGESIZE;
		} else {
			vdc->dring_max_cookies =
				(vdc->max_xfer_sz * vdc->block_size) / PAGESIZE;
		}
		vdc->dring_entry_size = (sizeof (vd_dring_entry_t) +
				(sizeof (ldc_mem_cookie_t) *
					(vdc->dring_max_cookies - 1)));
		vdc->dring_len = VD_DRING_LEN;

		status = ldc_mem_dring_create(vdc->dring_len,
				vdc->dring_entry_size, &vdc->ldc_dring_hdl);
		if ((vdc->ldc_dring_hdl == NULL) || (status != 0)) {
			DMSG(vdc, 0, "[%d] Descriptor ring creation failed",
					vdc->instance);
			return (status);
		}
		vdc->initialized |= VDC_DRING_INIT;
	}

	if ((vdc->initialized & VDC_DRING_BOUND) == 0) {
		DMSG(vdc, 0, "[%d] ldc_mem_dring_bind\n", vdc->instance);
		vdc->dring_cookie =
			kmem_zalloc(sizeof (ldc_mem_cookie_t), KM_SLEEP);

		status = ldc_mem_dring_bind(vdc->ldc_handle, vdc->ldc_dring_hdl,
				LDC_SHADOW_MAP|LDC_DIRECT_MAP, LDC_MEM_RW,
				&vdc->dring_cookie[0],
				&vdc->dring_cookie_count);
		if (status != 0) {
			DMSG(vdc, 0, "[%d] Failed to bind descriptor ring "
				"(%lx) to channel (%lx) status=%d\n",
				vdc->instance, vdc->ldc_dring_hdl,
				vdc->ldc_handle, status);
			return (status);
		}
		ASSERT(vdc->dring_cookie_count == 1);
		vdc->initialized |= VDC_DRING_BOUND;
	}

	status = ldc_mem_dring_info(vdc->ldc_dring_hdl, &vdc->dring_mem_info);
	if (status != 0) {
		DMSG(vdc, 0,
		    "[%d] Failed to get info for descriptor ring (%lx)\n",
		    vdc->instance, vdc->ldc_dring_hdl);
		return (status);
	}

	if ((vdc->initialized & VDC_DRING_LOCAL) == 0) {
		DMSG(vdc, 0, "[%d] local dring\n", vdc->instance);

		/* Allocate the local copy of this dring */
		vdc->local_dring =
			kmem_zalloc(vdc->dring_len * sizeof (vdc_local_desc_t),
						KM_SLEEP);
		vdc->initialized |= VDC_DRING_LOCAL;
	}

	/*
	 * Mark all DRing entries as free and initialize the private
	 * descriptor's memory handles. If any entry is initialized,
	 * we need to free it later so we set the bit in 'initialized'
	 * at the start.
	 */
	vdc->initialized |= VDC_DRING_ENTRY;
	for (i = 0; i < vdc->dring_len; i++) {
		dep = VDC_GET_DRING_ENTRY_PTR(vdc, i);
		dep->hdr.dstate = VIO_DESC_FREE;

		status = ldc_mem_alloc_handle(vdc->ldc_handle,
				&vdc->local_dring[i].desc_mhdl);
		if (status != 0) {
			DMSG(vdc, 0, "![%d] Failed to alloc mem handle for"
					" descriptor %d", vdc->instance, i);
			return (status);
		}
		vdc->local_dring[i].is_free = B_TRUE;
		vdc->local_dring[i].dep = dep;
	}

	/* Initialize the starting index */
	vdc->dring_curr_idx = 0;

	return (status);
}

/*
 * Function:
 *	vdc_destroy_descriptor_ring()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	None
 */
static void
vdc_destroy_descriptor_ring(vdc_t *vdc)
{
	vdc_local_desc_t	*ldep = NULL;	/* Local Dring Entry Pointer */
	ldc_mem_handle_t	mhdl = NULL;
	ldc_mem_info_t		minfo;
	int			status = -1;
	int			i;	/* loop */

	ASSERT(vdc != NULL);
	ASSERT(mutex_owned(&vdc->lock));

	DMSG(vdc, 0, "[%d] Entered\n", vdc->instance);

	if (vdc->initialized & VDC_DRING_ENTRY) {
		DMSG(vdc, 0,
		    "[%d] Removing Local DRing entries\n", vdc->instance);
		for (i = 0; i < vdc->dring_len; i++) {
			ldep = &vdc->local_dring[i];
			mhdl = ldep->desc_mhdl;

			if (mhdl == NULL)
				continue;

			if ((status = ldc_mem_info(mhdl, &minfo)) != 0) {
				DMSG(vdc, 0,
				    "ldc_mem_info returned an error: %d\n",
				    status);

				/*
				 * This must mean that the mem handle
				 * is not valid. Clear it out so that
				 * no one tries to use it.
				 */
				ldep->desc_mhdl = NULL;
				continue;
			}

			if (minfo.status == LDC_BOUND) {
				(void) ldc_mem_unbind_handle(mhdl);
			}

			(void) ldc_mem_free_handle(mhdl);

			ldep->desc_mhdl = NULL;
		}
		vdc->initialized &= ~VDC_DRING_ENTRY;
	}

	if (vdc->initialized & VDC_DRING_LOCAL) {
		DMSG(vdc, 0, "[%d] Freeing Local DRing\n", vdc->instance);
		kmem_free(vdc->local_dring,
				vdc->dring_len * sizeof (vdc_local_desc_t));
		vdc->initialized &= ~VDC_DRING_LOCAL;
	}

	if (vdc->initialized & VDC_DRING_BOUND) {
		DMSG(vdc, 0, "[%d] Unbinding DRing\n", vdc->instance);
		status = ldc_mem_dring_unbind(vdc->ldc_dring_hdl);
		if (status == 0) {
			vdc->initialized &= ~VDC_DRING_BOUND;
		} else {
			DMSG(vdc, 0, "[%d] Error %d unbinding DRing %lx",
				vdc->instance, status, vdc->ldc_dring_hdl);
		}
		kmem_free(vdc->dring_cookie, sizeof (ldc_mem_cookie_t));
	}

	if (vdc->initialized & VDC_DRING_INIT) {
		DMSG(vdc, 0, "[%d] Destroying DRing\n", vdc->instance);
		status = ldc_mem_dring_destroy(vdc->ldc_dring_hdl);
		if (status == 0) {
			vdc->ldc_dring_hdl = NULL;
			bzero(&vdc->dring_mem_info, sizeof (ldc_mem_info_t));
			vdc->initialized &= ~VDC_DRING_INIT;
		} else {
			DMSG(vdc, 0, "[%d] Error %d destroying DRing (%lx)",
				vdc->instance, status, vdc->ldc_dring_hdl);
		}
	}
}

/*
 * Function:
 *	vdc_map_to_shared_ring()
 *
 * Description:
 *	Copy contents of the local descriptor to the shared
 *	memory descriptor.
 *
 * Arguments:
 *	vdcp	- soft state pointer for this instance of the device driver.
 *	idx	- descriptor ring index
 *
 * Return Code:
 *	None
 */
static int
vdc_map_to_shared_dring(vdc_t *vdcp, int idx)
{
	vdc_local_desc_t	*ldep;
	vd_dring_entry_t	*dep;
	int			rv;

	ldep = &(vdcp->local_dring[idx]);

	/* for now leave in the old pop_mem_hdl stuff */
	if (ldep->nbytes > 0) {
		rv = vdc_populate_mem_hdl(vdcp, ldep);
		if (rv) {
			DMSG(vdcp, 0, "[%d] Cannot populate mem handle\n",
			    vdcp->instance);
			return (rv);
		}
	}

	/*
	 * fill in the data details into the DRing
	 */
	dep = ldep->dep;
	ASSERT(dep != NULL);

	dep->payload.req_id = VDC_GET_NEXT_REQ_ID(vdcp);
	dep->payload.operation = ldep->operation;
	dep->payload.addr = ldep->offset;
	dep->payload.nbytes = ldep->nbytes;
	dep->payload.status = (uint32_t)-1;	/* vds will set valid value */
	dep->payload.slice = ldep->slice;
	dep->hdr.dstate = VIO_DESC_READY;
	dep->hdr.ack = 1;		/* request an ACK for every message */

	return (0);
}

/*
 * Function:
 *	vdc_send_request
 *
 * Description:
 *	This routine writes the data to be transmitted to vds into the
 *	descriptor, notifies vds that the ring has been updated and
 *	then waits for the request to be processed.
 *
 * Arguments:
 *	vdcp	  - the soft state pointer
 *	operation - operation we want vds to perform (VD_OP_XXX)
 *	addr	  - address of data buf to be read/written.
 *	nbytes	  - number of bytes to read/write
 *	slice	  - the disk slice this request is for
 *	offset	  - relative disk offset
 *	cb_type   - type of call - STRATEGY or SYNC
 *	cb_arg	  - parameter to be sent to server (depends on VD_OP_XXX type)
 *			. mode for ioctl(9e)
 *			. LP64 diskaddr_t (block I/O)
 *	dir	  - direction of operation (READ/WRITE/BOTH)
 *
 * Return Codes:
 *	0
 *	EAGAIN
 *		EFAULT
 *		ENXIO
 *		EIO
 */
static int
vdc_send_request(vdc_t *vdcp, int operation, caddr_t addr,
    size_t nbytes, int slice, diskaddr_t offset, int cb_type,
    void *cb_arg, vio_desc_direction_t dir)
{
	ASSERT(vdcp != NULL);
	ASSERT(slice < V_NUMPAR);

	mutex_enter(&vdcp->lock);

	do {
		while (vdcp->state != VDC_STATE_RUNNING)
			cv_wait(&vdcp->running_cv, &vdcp->lock);

	} while (vdc_populate_descriptor(vdcp, operation, addr,
	    nbytes, slice, offset, cb_type, cb_arg, dir));

	mutex_exit(&vdcp->lock);
	return (0);
}


/*
 * Function:
 *	vdc_populate_descriptor
 *
 * Description:
 *	This routine writes the data to be transmitted to vds into the
 *	descriptor, notifies vds that the ring has been updated and
 *	then waits for the request to be processed.
 *
 * Arguments:
 *	vdcp	  - the soft state pointer
 *	operation - operation we want vds to perform (VD_OP_XXX)
 *	addr	  - address of data buf to be read/written.
 *	nbytes	  - number of bytes to read/write
 *	slice	  - the disk slice this request is for
 *	offset	  - relative disk offset
 *	cb_type   - type of call - STRATEGY or SYNC
 *	cb_arg	  - parameter to be sent to server (depends on VD_OP_XXX type)
 *			. mode for ioctl(9e)
 *			. LP64 diskaddr_t (block I/O)
 *	dir	  - direction of operation (READ/WRITE/BOTH)
 *
 * Return Codes:
 *	0
 *	EAGAIN
 *		EFAULT
 *		ENXIO
 *		EIO
 */
static int
vdc_populate_descriptor(vdc_t *vdcp, int operation, caddr_t addr,
    size_t nbytes, int slice, diskaddr_t offset, int cb_type,
    void *cb_arg, vio_desc_direction_t dir)
{
	vdc_local_desc_t	*local_dep = NULL; /* Local Dring Pointer */
	int			idx;		/* Index of DRing entry used */
	int			next_idx;
	vio_dring_msg_t		dmsg;
	size_t			msglen;
	int			rv;

	ASSERT(MUTEX_HELD(&vdcp->lock));
	vdcp->threads_pending++;
loop:
	DMSG(vdcp, 2, ": dring_curr_idx = %d\n", vdcp->dring_curr_idx);

	/* Get next available D-Ring entry */
	idx = vdcp->dring_curr_idx;
	local_dep = &(vdcp->local_dring[idx]);

	if (!local_dep->is_free) {
		DMSG(vdcp, 2, "[%d]: dring full - waiting for space\n",
		    vdcp->instance);
		cv_wait(&vdcp->dring_free_cv, &vdcp->lock);
		if (vdcp->state == VDC_STATE_RUNNING ||
		    vdcp->state == VDC_STATE_HANDLE_PENDING) {
			goto loop;
		}
		vdcp->threads_pending--;
		return (ECONNRESET);
	}

	next_idx = idx + 1;
	if (next_idx >= vdcp->dring_len)
		next_idx = 0;
	vdcp->dring_curr_idx = next_idx;

	ASSERT(local_dep->is_free);

	local_dep->operation = operation;
	local_dep->addr = addr;
	local_dep->nbytes = nbytes;
	local_dep->slice = slice;
	local_dep->offset = offset;
	local_dep->cb_type = cb_type;
	local_dep->cb_arg = cb_arg;
	local_dep->dir = dir;

	local_dep->is_free = B_FALSE;

	rv = vdc_map_to_shared_dring(vdcp, idx);
	if (rv) {
		DMSG(vdcp, 0, "[%d]: cannot bind memory - waiting ..\n",
		    vdcp->instance);
		/* free the descriptor */
		local_dep->is_free = B_TRUE;
		vdcp->dring_curr_idx = idx;
		cv_wait(&vdcp->membind_cv, &vdcp->lock);
		if (vdcp->state == VDC_STATE_RUNNING ||
		    vdcp->state == VDC_STATE_HANDLE_PENDING) {
			goto loop;
		}
		vdcp->threads_pending--;
		return (ECONNRESET);
	}

	/*
	 * Send a msg with the DRing details to vds
	 */
	VIO_INIT_DRING_DATA_TAG(dmsg);
	VDC_INIT_DRING_DATA_MSG_IDS(dmsg, vdcp);
	dmsg.dring_ident = vdcp->dring_ident;
	dmsg.start_idx = idx;
	dmsg.end_idx = idx;
	vdcp->seq_num++;

	DTRACE_IO2(send, vio_dring_msg_t *, &dmsg, vdc_t *, vdcp);

	DMSG(vdcp, 2, "ident=0x%lx, st=%u, end=%u, seq=%ld\n",
	    vdcp->dring_ident, dmsg.start_idx, dmsg.end_idx, dmsg.seq_num);

	/*
	 * note we're still holding the lock here to
	 * make sure the message goes out in order !!!...
	 */
	msglen = sizeof (dmsg);
	rv = vdc_send(vdcp, (caddr_t)&dmsg, &msglen);
	switch (rv) {
	case ECONNRESET:
		/*
		 * vdc_send initiates the reset on failure.
		 * Since the transaction has already been put
		 * on the local dring, it will automatically get
		 * retried when the channel is reset. Given that,
		 * it is ok to just return success even though the
		 * send failed.
		 */
		rv = 0;
		break;

	case 0: /* EOK */
		DMSG(vdcp, 1, "sent via LDC: rv=%d\n", rv);
		break;

	default:
		goto cleanup_and_exit;
	}

	vdcp->threads_pending--;
	return (rv);

cleanup_and_exit:
	DMSG(vdcp, 0, "unexpected error, rv=%d\n", rv);
	return (ENXIO);
}

/*
 * Function:
 *	vdc_do_sync_op
 *
 * Description:
 * 	Wrapper around vdc_populate_descriptor that blocks until the
 * 	response to the message is available.
 *
 * Arguments:
 *	vdcp	  - the soft state pointer
 *	operation - operation we want vds to perform (VD_OP_XXX)
 *	addr	  - address of data buf to be read/written.
 *	nbytes	  - number of bytes to read/write
 *	slice	  - the disk slice this request is for
 *	offset	  - relative disk offset
 *	cb_type   - type of call - STRATEGY or SYNC
 *	cb_arg	  - parameter to be sent to server (depends on VD_OP_XXX type)
 *			. mode for ioctl(9e)
 *			. LP64 diskaddr_t (block I/O)
 *	dir	  - direction of operation (READ/WRITE/BOTH)
 *
 * Return Codes:
 *	0
 *	EAGAIN
 *		EFAULT
 *		ENXIO
 *		EIO
 */
static int
vdc_do_sync_op(vdc_t *vdcp, int operation, caddr_t addr, size_t nbytes,
    int slice, diskaddr_t offset, int cb_type, void *cb_arg,
    vio_desc_direction_t dir)
{
	int status;

	ASSERT(cb_type == CB_SYNC);

	/*
	 * Grab the lock, if blocked wait until the server
	 * response causes us to wake up again.
	 */
	mutex_enter(&vdcp->lock);
	vdcp->sync_op_cnt++;
	while (vdcp->sync_op_blocked && vdcp->state != VDC_STATE_DETACH)
		cv_wait(&vdcp->sync_blocked_cv, &vdcp->lock);

	if (vdcp->state == VDC_STATE_DETACH) {
		cv_broadcast(&vdcp->sync_blocked_cv);
		vdcp->sync_op_cnt--;
		mutex_exit(&vdcp->lock);
		return (ENXIO);
	}

	/* now block anyone other thread entering after us */
	vdcp->sync_op_blocked = B_TRUE;
	vdcp->sync_op_pending = B_TRUE;
	mutex_exit(&vdcp->lock);

	/*
	 * No need to check return value - will return error only
	 * in the DETACH case and we can fall through
	 */
	(void) vdc_send_request(vdcp, operation, addr,
	    nbytes, slice, offset, cb_type, cb_arg, dir);

	/*
	 * block until our transaction completes.
	 * Also anyone else waiting also gets to go next.
	 */
	mutex_enter(&vdcp->lock);
	while (vdcp->sync_op_pending && vdcp->state != VDC_STATE_DETACH)
		cv_wait(&vdcp->sync_pending_cv, &vdcp->lock);

	DMSG(vdcp, 2, ": operation returned %d\n", vdcp->sync_op_status);
	if (vdcp->state == VDC_STATE_DETACH)
		status = ENXIO;
	else
		status = vdcp->sync_op_status;
	vdcp->sync_op_status = 0;
	vdcp->sync_op_blocked = B_FALSE;
	vdcp->sync_op_cnt--;

	/* signal the next waiting thread */
	cv_signal(&vdcp->sync_blocked_cv);
	mutex_exit(&vdcp->lock);

	return (status);
}


/*
 * Function:
 *	vdc_drain_response()
 *
 * Description:
 * 	When a guest is panicking, the completion of requests needs to be
 * 	handled differently because interrupts are disabled and vdc
 * 	will not get messages. We have to poll for the messages instead.
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_drain_response(vdc_t *vdc)
{
	int 			rv, idx, retries;
	size_t			msglen;
	vdc_local_desc_t 	*ldep = NULL;	/* Local Dring Entry Pointer */
	vio_dring_msg_t		dmsg;

	mutex_enter(&vdc->lock);

	retries = 0;
	for (;;) {
		msglen = sizeof (dmsg);
		rv = ldc_read(vdc->ldc_handle, (caddr_t)&dmsg, &msglen);
		if (rv) {
			rv = EINVAL;
			break;
		}

		/*
		 * if there are no packets wait and check again
		 */
		if ((rv == 0) && (msglen == 0)) {
			if (retries++ > vdc_dump_retries) {
				rv = EAGAIN;
				break;
			}

			drv_usecwait(vdc_usec_timeout_dump);
			continue;
		}

		/*
		 * Ignore all messages that are not ACKs/NACKs to
		 * DRing requests.
		 */
		if ((dmsg.tag.vio_msgtype != VIO_TYPE_DATA) ||
		    (dmsg.tag.vio_subtype_env != VIO_DRING_DATA)) {
			DMSG(vdc, 0, "discard pkt: type=%d sub=%d env=%d\n",
			    dmsg.tag.vio_msgtype,
			    dmsg.tag.vio_subtype,
			    dmsg.tag.vio_subtype_env);
			continue;
		}

		/*
		 * set the appropriate return value for the current request.
		 */
		switch (dmsg.tag.vio_subtype) {
		case VIO_SUBTYPE_ACK:
			rv = 0;
			break;
		case VIO_SUBTYPE_NACK:
			rv = EAGAIN;
			break;
		default:
			continue;
		}

		idx = dmsg.start_idx;
		if (idx >= vdc->dring_len) {
			DMSG(vdc, 0, "[%d] Bogus ack data : start %d\n",
			    vdc->instance, idx);
			continue;
		}
		ldep = &vdc->local_dring[idx];
		if (ldep->dep->hdr.dstate != VIO_DESC_DONE) {
			DMSG(vdc, 0, "[%d] Entry @ %d - state !DONE %d\n",
			    vdc->instance, idx, ldep->dep->hdr.dstate);
			continue;
		}

		DMSG(vdc, 1, "[%d] Depopulating idx=%d state=%d\n",
		    vdc->instance, idx, ldep->dep->hdr.dstate);
		rv = vdc_depopulate_descriptor(vdc, idx);
		if (rv) {
			DMSG(vdc, 0,
			    "[%d] Entry @ %d - depopulate failed ..\n",
			    vdc->instance, idx);
		}

		/* if this is the last descriptor - break out of loop */
		if ((idx + 1) % vdc->dring_len == vdc->dring_curr_idx)
			break;
	}

	mutex_exit(&vdc->lock);
	DMSG(vdc, 0, "End idx=%d\n", idx);

	return (rv);
}


/*
 * Function:
 *	vdc_depopulate_descriptor()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *	idx	- Index of the Descriptor Ring entry being modified
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_depopulate_descriptor(vdc_t *vdc, uint_t idx)
{
	vd_dring_entry_t *dep = NULL;		/* Dring Entry Pointer */
	vdc_local_desc_t *ldep = NULL;		/* Local Dring Entry Pointer */
	int		status = ENXIO;
	int		operation;
	int		rv = 0;

	ASSERT(vdc != NULL);
	ASSERT(idx < vdc->dring_len);
	ldep = &vdc->local_dring[idx];
	ASSERT(ldep != NULL);
	ASSERT(MUTEX_HELD(&vdc->lock));

	DMSG(vdc, 2, ": idx = %d\n", idx);
	dep = ldep->dep;
	ASSERT(dep != NULL);
	ASSERT((dep->hdr.dstate == VIO_DESC_DONE) ||
			(dep->payload.status == ECANCELED));

	VDC_MARK_DRING_ENTRY_FREE(vdc, idx);

	ldep->is_free = B_TRUE;
	DMSG(vdc, 2, ": is_free = %d\n", ldep->is_free);
	status = dep->payload.status;
	operation = dep->payload.operation;

	/* the DKIO FLUSH operation never bind handles so we can return now */
	if (operation == VD_OP_FLUSH)
		return (status);

	/*
	 * If the upper layer passed in a misaligned address we copied the
	 * data into an aligned buffer before sending it to LDC - we now
	 * copy it back to the original buffer.
	 */
	if (ldep->align_addr) {
		ASSERT(ldep->addr != NULL);
		ASSERT(dep->payload.nbytes > 0);

		bcopy(ldep->align_addr, ldep->addr, dep->payload.nbytes);
		kmem_free(ldep->align_addr,
			sizeof (caddr_t) * P2ROUNDUP(dep->payload.nbytes, 8));
		ldep->align_addr = NULL;
	}

	rv = ldc_mem_unbind_handle(ldep->desc_mhdl);
	if (rv != 0) {
		DMSG(vdc, 0, "?[%d] unbind mhdl 0x%lx @ idx %d failed (%d)",
				vdc->instance, ldep->desc_mhdl, idx, rv);
		/*
		 * The error returned by the vDisk server is more informative
		 * and thus has a higher priority but if it isn't set we ensure
		 * that this function returns an error.
		 */
		if (status == 0)
			status = EINVAL;
	}

	cv_signal(&vdc->membind_cv);
	cv_signal(&vdc->dring_free_cv);

	return (status);
}

/*
 * Function:
 *	vdc_populate_mem_hdl()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *	idx	- Index of the Descriptor Ring entry being modified
 *	addr	- virtual address being mapped in
 *	nybtes	- number of bytes in 'addr'
 *	operation - the vDisk operation being performed (VD_OP_xxx)
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_populate_mem_hdl(vdc_t *vdcp, vdc_local_desc_t *ldep)
{
	vd_dring_entry_t	*dep = NULL;
	ldc_mem_handle_t	mhdl;
	caddr_t			vaddr;
	size_t			nbytes;
	uint8_t			perm = LDC_MEM_RW;
	uint8_t			maptype;
	int			rv = 0;
	int			i;

	ASSERT(vdcp != NULL);

	dep = ldep->dep;
	mhdl = ldep->desc_mhdl;

	switch (ldep->dir) {
	case VIO_read_dir:
		perm = LDC_MEM_W;
		break;

	case VIO_write_dir:
		perm = LDC_MEM_R;
		break;

	case VIO_both_dir:
		perm = LDC_MEM_RW;
		break;

	default:
		ASSERT(0);	/* catch bad programming in vdc */
	}

	/*
	 * LDC expects any addresses passed in to be 8-byte aligned. We need
	 * to copy the contents of any misaligned buffers to a newly allocated
	 * buffer and bind it instead (and copy the the contents back to the
	 * original buffer passed in when depopulating the descriptor)
	 */
	vaddr = ldep->addr;
	nbytes = ldep->nbytes;
	if (((uint64_t)vaddr & 0x7) != 0) {
		ASSERT(ldep->align_addr == NULL);
		ldep->align_addr =
			kmem_alloc(sizeof (caddr_t) *
				P2ROUNDUP(nbytes, 8), KM_SLEEP);
		DMSG(vdcp, 0, "[%d] Misaligned address %p reallocating "
		    "(buf=%p nb=%ld op=%d)\n",
		    vdcp->instance, (void *)vaddr, (void *)ldep->align_addr,
		    nbytes, ldep->operation);
		if (perm != LDC_MEM_W)
			bcopy(vaddr, ldep->align_addr, nbytes);
		vaddr = ldep->align_addr;
	}

	maptype = LDC_IO_MAP|LDC_SHADOW_MAP|LDC_DIRECT_MAP;
	rv = ldc_mem_bind_handle(mhdl, vaddr, P2ROUNDUP(nbytes, 8),
		maptype, perm, &dep->payload.cookie[0],
		&dep->payload.ncookies);
	DMSG(vdcp, 2, "[%d] bound mem handle; ncookies=%d\n",
			vdcp->instance, dep->payload.ncookies);
	if (rv != 0) {
		DMSG(vdcp, 0, "[%d] Failed to bind LDC memory handle "
		    "(mhdl=%p, buf=%p, err=%d)\n",
		    vdcp->instance, (void *)mhdl, (void *)vaddr, rv);
		if (ldep->align_addr) {
			kmem_free(ldep->align_addr,
				sizeof (caddr_t) * P2ROUNDUP(nbytes, 8));
			ldep->align_addr = NULL;
		}
		return (EAGAIN);
	}

	/*
	 * Get the other cookies (if any).
	 */
	for (i = 1; i < dep->payload.ncookies; i++) {
		rv = ldc_mem_nextcookie(mhdl, &dep->payload.cookie[i]);
		if (rv != 0) {
			(void) ldc_mem_unbind_handle(mhdl);
			DMSG(vdcp, 0, "?[%d] Failed to get next cookie "
					"(mhdl=%lx cnum=%d), err=%d",
					vdcp->instance, mhdl, i, rv);
			if (ldep->align_addr) {
				kmem_free(ldep->align_addr,
					sizeof (caddr_t) * dep->payload.nbytes);
				ldep->align_addr = NULL;
			}
			return (EAGAIN);
		}
	}

	return (rv);
}

/*
 * Interrupt handlers for messages from LDC
 */

/*
 * Function:
 *	vdc_handle_cb()
 *
 * Description:
 *
 * Arguments:
 *	event	- Type of event (LDC_EVT_xxx) that triggered the callback
 *	arg	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static uint_t
vdc_handle_cb(uint64_t event, caddr_t arg)
{
	ldc_status_t	ldc_state;
	int		rv = 0;

	vdc_t	*vdc = (vdc_t *)(void *)arg;

	ASSERT(vdc != NULL);

	DMSG(vdc, 1, "evt=%lx seqID=%ld\n", event, vdc->seq_num);

	/*
	 * Depending on the type of event that triggered this callback,
	 * we modify the handshake state or read the data.
	 *
	 * NOTE: not done as a switch() as event could be triggered by
	 * a state change and a read request. Also the ordering	of the
	 * check for the event types is deliberate.
	 */
	if (event & LDC_EVT_UP) {
		DMSG(vdc, 0, "[%d] Received LDC_EVT_UP\n", vdc->instance);

		mutex_enter(&vdc->lock);

		/* get LDC state */
		rv = ldc_status(vdc->ldc_handle, &ldc_state);
		if (rv != 0) {
			DMSG(vdc, 0, "[%d] Couldn't get LDC status %d",
			    vdc->instance, rv);
			return (LDC_SUCCESS);
		}
		if (vdc->ldc_state != LDC_UP && ldc_state == LDC_UP) {
			/*
			 * Reset the transaction sequence numbers when
			 * LDC comes up. We then kick off the handshake
			 * negotiation with the vDisk server.
			 */
			vdc->seq_num = 1;
			vdc->seq_num_reply = 0;
			vdc->ldc_state = ldc_state;
			cv_signal(&vdc->initwait_cv);
		}

		mutex_exit(&vdc->lock);
	}

	if (event & LDC_EVT_READ) {
		DMSG(vdc, 0, "[%d] Received LDC_EVT_READ\n", vdc->instance);
		mutex_enter(&vdc->read_lock);
		cv_signal(&vdc->read_cv);
		vdc->read_state = VDC_READ_PENDING;
		mutex_exit(&vdc->read_lock);

		/* that's all we have to do - no need to handle DOWN/RESET */
		return (LDC_SUCCESS);
	}

	if (event & (LDC_EVT_RESET|LDC_EVT_DOWN)) {

		DMSG(vdc, 0, "[%d] Received LDC RESET event\n", vdc->instance);

		mutex_enter(&vdc->lock);
		/*
		 * Need to wake up any readers so they will
		 * detect that a reset has occurred.
		 */
		mutex_enter(&vdc->read_lock);
		if ((vdc->read_state == VDC_READ_WAITING) ||
		    (vdc->read_state == VDC_READ_RESET))
			cv_signal(&vdc->read_cv);
		vdc->read_state = VDC_READ_RESET;
		mutex_exit(&vdc->read_lock);

		/* wake up any threads waiting for connection to come up */
		if (vdc->state == VDC_STATE_INIT_WAITING) {
			vdc->state = VDC_STATE_RESETTING;
			cv_signal(&vdc->initwait_cv);
		}

		mutex_exit(&vdc->lock);
	}

	if (event & ~(LDC_EVT_UP | LDC_EVT_RESET | LDC_EVT_DOWN | LDC_EVT_READ))
		DMSG(vdc, 0, "![%d] Unexpected LDC event (%lx) received",
				vdc->instance, event);

	return (LDC_SUCCESS);
}

/*
 * Function:
 *	vdc_wait_for_response()
 *
 * Description:
 *	Block waiting for a response from the server. If there is
 *	no data the thread block on the read_cv that is signalled
 *	by the callback when an EVT_READ occurs.
 *
 * Arguments:
 *	vdcp	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_wait_for_response(vdc_t *vdcp, vio_msg_t *msgp)
{
	size_t		nbytes = sizeof (*msgp);
	int		status;

	ASSERT(vdcp != NULL);

	DMSG(vdcp, 1, "[%d] Entered\n", vdcp->instance);

	status = vdc_recv(vdcp, msgp, &nbytes);
	DMSG(vdcp, 3, "vdc_read() done.. status=0x%x size=0x%x\n",
		status, (int)nbytes);
	if (status) {
		DMSG(vdcp, 0, "?[%d] Error %d reading LDC msg\n",
				vdcp->instance, status);
		return (status);
	}

	if (nbytes < sizeof (vio_msg_tag_t)) {
		DMSG(vdcp, 0, "?[%d] Expect %lu bytes; recv'd %lu\n",
			vdcp->instance, sizeof (vio_msg_tag_t), nbytes);
		return (ENOMSG);
	}

	DMSG(vdcp, 2, "[%d] (%x/%x/%x)\n", vdcp->instance,
	    msgp->tag.vio_msgtype,
	    msgp->tag.vio_subtype,
	    msgp->tag.vio_subtype_env);

	/*
	 * Verify the Session ID of the message
	 *
	 * Every message after the Version has been negotiated should
	 * have the correct session ID set.
	 */
	if ((msgp->tag.vio_sid != vdcp->session_id) &&
	    (msgp->tag.vio_subtype_env != VIO_VER_INFO)) {
		DMSG(vdcp, 0, "[%d] Invalid SID: received 0x%x, "
				"expected 0x%lx [seq num %lx @ %d]",
			vdcp->instance, msgp->tag.vio_sid,
			vdcp->session_id,
			((vio_dring_msg_t *)msgp)->seq_num,
			((vio_dring_msg_t *)msgp)->start_idx);
		return (ENOMSG);
	}
	return (0);
}


/*
 * Function:
 *	vdc_resubmit_backup_dring()
 *
 * Description:
 *	Resubmit each descriptor in the backed up dring to
 * 	vDisk server. The Dring was backed up during connection
 *	reset.
 *
 * Arguments:
 *	vdcp	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_resubmit_backup_dring(vdc_t *vdcp)
{
	int		count;
	int		b_idx;
	int		rv;
	int		dring_size;
	int		status;
	vio_msg_t	vio_msg;
	vdc_local_desc_t	*curr_ldep;

	ASSERT(MUTEX_NOT_HELD(&vdcp->lock));
	ASSERT(vdcp->state == VDC_STATE_HANDLE_PENDING);

	DMSG(vdcp, 1, "restoring pending dring entries (len=%d, tail=%d)\n",
	    vdcp->local_dring_backup_len, vdcp->local_dring_backup_tail);

	/*
	 * Walk the backup copy of the local descriptor ring and
	 * resubmit all the outstanding transactions.
	 */
	b_idx = vdcp->local_dring_backup_tail;
	for (count = 0; count < vdcp->local_dring_backup_len; count++) {

		curr_ldep = &(vdcp->local_dring_backup[b_idx]);

		/* only resubmit oustanding transactions */
		if (!curr_ldep->is_free) {

			DMSG(vdcp, 1, "resubmitting entry idx=%x\n", b_idx);
			mutex_enter(&vdcp->lock);
			rv = vdc_populate_descriptor(vdcp, curr_ldep->operation,
			    curr_ldep->addr, curr_ldep->nbytes,
			    curr_ldep->slice, curr_ldep->offset,
			    curr_ldep->cb_type, curr_ldep->cb_arg,
			    curr_ldep->dir);
			mutex_exit(&vdcp->lock);
			if (rv) {
				DMSG(vdcp, 1, "[%d] cannot resubmit entry %d\n",
				    vdcp->instance, b_idx);
				return (rv);
			}

			/* Wait for the response message. */
			DMSG(vdcp, 1, "waiting for response to idx=%x\n",
			    b_idx);
			status = vdc_wait_for_response(vdcp, &vio_msg);
			if (status) {
				DMSG(vdcp, 1, "[%d] wait_for_response "
				    "returned err=%d\n", vdcp->instance,
				    status);
				return (status);
			}

			DMSG(vdcp, 1, "processing msg for idx=%x\n", b_idx);
			status = vdc_process_data_msg(vdcp, &vio_msg);
			if (status) {
				DMSG(vdcp, 1, "[%d] process_data_msg "
				    "returned err=%d\n", vdcp->instance,
				    status);
				return (status);
			}
		}

		/* get the next element to submit */
		if (++b_idx >= vdcp->local_dring_backup_len)
			b_idx = 0;
	}

	/* all done - now clear up pending dring copy */
	dring_size = vdcp->local_dring_backup_len *
		sizeof (vdcp->local_dring_backup[0]);

	(void) kmem_free(vdcp->local_dring_backup, dring_size);

	vdcp->local_dring_backup = NULL;

	return (0);
}

/*
 * Function:
 *	vdc_backup_local_dring()
 *
 * Description:
 *	Backup the current dring in the event of a reset. The Dring
 *	transactions will be resubmitted to the server when the
 *	connection is restored.
 *
 * Arguments:
 *	vdcp	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	NONE
 */
static void
vdc_backup_local_dring(vdc_t *vdcp)
{
	int dring_size;

	ASSERT(vdcp->state == VDC_STATE_RESETTING);

	/*
	 * If the backup dring is stil around, it means
	 * that the last restore did not complete. However,
	 * since we never got back into the running state,
	 * the backup copy we have is still valid.
	 */
	if (vdcp->local_dring_backup != NULL) {
		DMSG(vdcp, 1, "reusing local descriptor ring backup "
		    "(len=%d, tail=%d)\n", vdcp->local_dring_backup_len,
		    vdcp->local_dring_backup_tail);
		return;
	}

	DMSG(vdcp, 1, "backing up the local descriptor ring (len=%d, "
	    "tail=%d)\n", vdcp->dring_len, vdcp->dring_curr_idx);

	dring_size = vdcp->dring_len * sizeof (vdcp->local_dring[0]);

	vdcp->local_dring_backup = kmem_alloc(dring_size, KM_SLEEP);
	bcopy(vdcp->local_dring, vdcp->local_dring_backup, dring_size);

	vdcp->local_dring_backup_tail = vdcp->dring_curr_idx;
	vdcp->local_dring_backup_len = vdcp->dring_len;
}

/* -------------------------------------------------------------------------- */

/*
 * The following functions process the incoming messages from vds
 */

/*
 * Function:
 *      vdc_process_msg_thread()
 *
 * Description:
 *
 *	Main VDC message processing thread. Each vDisk instance
 * 	consists of a copy of this thread. This thread triggers
 * 	all the handshakes and data exchange with the server. It
 * 	also handles all channel resets
 *
 * Arguments:
 *      vdc     - soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *      None
 */
static void
vdc_process_msg_thread(vdc_t *vdcp)
{
	int	status;

	mutex_enter(&vdcp->lock);

	for (;;) {

#define	Q(_s)	(vdcp->state == _s) ? #_s :
		DMSG(vdcp, 3, "state = %d (%s)\n", vdcp->state,
		Q(VDC_STATE_INIT)
		Q(VDC_STATE_INIT_WAITING)
		Q(VDC_STATE_NEGOTIATE)
		Q(VDC_STATE_HANDLE_PENDING)
		Q(VDC_STATE_RUNNING)
		Q(VDC_STATE_RESETTING)
		Q(VDC_STATE_DETACH)
		"UNKNOWN");

		switch (vdcp->state) {
		case VDC_STATE_INIT:

			/* Check if have re-initializing repeatedly */
			if (vdcp->hshake_cnt++ > VDC_RETRIES) {
				vdcp->state = VDC_STATE_DETACH;
				break;
			}

			/* Bring up connection with vds via LDC */
			status = vdc_start_ldc_connection(vdcp);
			switch (status) {
			case EINVAL:
				DMSG(vdcp, 0, "[%d] Could not start LDC",
				    vdcp->instance);
				vdcp->state = VDC_STATE_DETACH;
				break;
			case 0:
				vdcp->state = VDC_STATE_INIT_WAITING;
				break;
			default:
				vdcp->state = VDC_STATE_INIT_WAITING;
				break;
			}
			break;

		case VDC_STATE_INIT_WAITING:

			/*
			 * Let the callback event move us on
			 * when channel is open to server
			 */
			while (vdcp->ldc_state != LDC_UP) {
				cv_wait(&vdcp->initwait_cv, &vdcp->lock);
				if (vdcp->state != VDC_STATE_INIT_WAITING) {
					DMSG(vdcp, 0,
				"state moved to %d out from under us...\n",
					    vdcp->state);

					break;
				}
			}
			if (vdcp->state == VDC_STATE_INIT_WAITING &&
			    vdcp->ldc_state == LDC_UP) {
				vdcp->state = VDC_STATE_NEGOTIATE;
			}
			break;

		case VDC_STATE_NEGOTIATE:
			switch (status = vdc_ver_negotiation(vdcp)) {
			case 0:
				break;
			default:
				DMSG(vdcp, 0, "ver negotiate failed (%d)..\n",
				    status);
				goto reset;
			}

			switch (status = vdc_attr_negotiation(vdcp)) {
			case 0:
				break;
			default:
				DMSG(vdcp, 0, "attr negotiate failed (%d)..\n",
				    status);
				goto reset;
			}

			switch (status = vdc_dring_negotiation(vdcp)) {
			case 0:
				break;
			default:
				DMSG(vdcp, 0, "dring negotiate failed (%d)..\n",
				    status);
				goto reset;
			}

			switch (status = vdc_rdx_exchange(vdcp)) {
			case 0:
				vdcp->state = VDC_STATE_HANDLE_PENDING;
				goto done;
			default:
				DMSG(vdcp, 0, "RDX xchg failed ..(%d)\n",
				    status);
				goto reset;
			}
reset:
			DMSG(vdcp, 0, "negotiation failed: resetting (%d)\n",
			    status);
			vdcp->state = VDC_STATE_RESETTING;
done:
			DMSG(vdcp, 0, "negotiation complete (state=0x%x)...\n",
			    vdcp->state);
			break;

		case VDC_STATE_HANDLE_PENDING:

			mutex_exit(&vdcp->lock);
			status = vdc_resubmit_backup_dring(vdcp);
			mutex_enter(&vdcp->lock);

			if (status)
				vdcp->state = VDC_STATE_RESETTING;
			else
				vdcp->state = VDC_STATE_RUNNING;

			break;

		/* enter running state */
		case VDC_STATE_RUNNING:
			/*
			 * Signal anyone waiting for the connection
			 * to come on line.
			 */
			vdcp->hshake_cnt = 0;
			cv_broadcast(&vdcp->running_cv);
			mutex_exit(&vdcp->lock);

			for (;;) {
				vio_msg_t msg;
				status = vdc_wait_for_response(vdcp, &msg);
				if (status) break;

				DMSG(vdcp, 1, "[%d] new pkt(s) available\n",
					vdcp->instance);
				status = vdc_process_data_msg(vdcp, &msg);
				if (status) {
					DMSG(vdcp, 1, "[%d] process_data_msg "
					    "returned err=%d\n", vdcp->instance,
					    status);
					break;
				}

			}

			mutex_enter(&vdcp->lock);

			vdcp->state = VDC_STATE_RESETTING;
			break;

		case VDC_STATE_RESETTING:
			DMSG(vdcp, 0, "Initiating channel reset "
			    "(pending = %d)\n", (int)vdcp->threads_pending);

			if (vdcp->self_reset) {
				DMSG(vdcp, 0,
				    "[%d] calling stop_ldc_connection.\n",
				    vdcp->instance);
				status = vdc_stop_ldc_connection(vdcp);
				vdcp->self_reset = B_FALSE;
			}

			/*
			 * Wait for all threads currently waiting
			 * for a free dring entry to use.
			 */
			while (vdcp->threads_pending) {
				cv_broadcast(&vdcp->membind_cv);
				cv_broadcast(&vdcp->dring_free_cv);
				mutex_exit(&vdcp->lock);
				/* let them wake up */
				drv_usecwait(vdc_min_timeout_ldc);
				mutex_enter(&vdcp->lock);
			}

			ASSERT(vdcp->threads_pending == 0);

			/* Sanity check that no thread is receiving */
			ASSERT(vdcp->read_state != VDC_READ_WAITING);

			vdcp->read_state = VDC_READ_IDLE;

			vdc_backup_local_dring(vdcp);

			/* cleanup the old d-ring */
			vdc_destroy_descriptor_ring(vdcp);

			/* go and start again */
			vdcp->state = VDC_STATE_INIT;

			break;

		case VDC_STATE_DETACH:
			DMSG(vdcp, 0, "[%d] Reset thread exit cleanup ..\n",
			    vdcp->instance);

			while (vdcp->sync_op_pending) {
				cv_signal(&vdcp->sync_pending_cv);
				cv_signal(&vdcp->sync_blocked_cv);
				mutex_exit(&vdcp->lock);
				drv_usecwait(vdc_min_timeout_ldc);
				mutex_enter(&vdcp->lock);
			}

			cv_signal(&vdcp->running_cv);
			mutex_exit(&vdcp->lock);

			DMSG(vdcp, 0, "[%d] Msg processing thread exiting ..\n",
				vdcp->instance);
			thread_exit();
			break;
		}
	}
}


/*
 * Function:
 *	vdc_process_data_msg()
 *
 * Description:
 *	This function is called by the message processing thread each time
 *	a message with a msgtype of VIO_TYPE_DATA is received. It will either
 *	be an ACK or NACK from vds[1] which vdc handles as follows.
 *		ACK	- wake up the waiting thread
 *		NACK	- resend any messages necessary
 *
 *	[1] Although the message format allows it, vds should not send a
 *	    VIO_SUBTYPE_INFO message to vdc asking it to read data; if for
 *	    some bizarre reason it does, vdc will reset the connection.
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *	msg	- the LDC message sent by vds
 *
 * Return Code:
 *	0	- Success.
 *	> 0	- error value returned by LDC
 */
static int
vdc_process_data_msg(vdc_t *vdcp, vio_msg_t *msg)
{
	int			status = 0;
	vio_dring_msg_t		*dring_msg;
	vdc_local_desc_t	*ldep = NULL;
	int			start, end;
	int			idx;

	dring_msg = (vio_dring_msg_t *)msg;

	ASSERT(msg->tag.vio_msgtype == VIO_TYPE_DATA);
	ASSERT(vdcp != NULL);

	mutex_enter(&vdcp->lock);

	/*
	 * Check to see if the message has bogus data
	 */
	idx = start = dring_msg->start_idx;
	end = dring_msg->end_idx;
	if ((start >= vdcp->dring_len) ||
	    (end >= vdcp->dring_len) || (end < -1)) {
		DMSG(vdcp, 0, "[%d] Bogus ACK data : start %d, end %d\n",
			vdcp->instance, start, end);
		mutex_exit(&vdcp->lock);
		return (EINVAL);
	}

	/*
	 * Verify that the sequence number is what vdc expects.
	 */
	switch (vdc_verify_seq_num(vdcp, dring_msg)) {
	case VDC_SEQ_NUM_TODO:
		break;	/* keep processing this message */
	case VDC_SEQ_NUM_SKIP:
		mutex_exit(&vdcp->lock);
		return (0);
	case VDC_SEQ_NUM_INVALID:
		mutex_exit(&vdcp->lock);
		DMSG(vdcp, 0, "[%d] invalid seqno\n", vdcp->instance);
		return (ENXIO);
	}

	if (msg->tag.vio_subtype == VIO_SUBTYPE_NACK) {
		DMSG(vdcp, 0, "[%d] DATA NACK\n", vdcp->instance);
		VDC_DUMP_DRING_MSG(dring_msg);
		mutex_exit(&vdcp->lock);
		return (EIO);

	} else if (msg->tag.vio_subtype == VIO_SUBTYPE_INFO) {
		mutex_exit(&vdcp->lock);
		return (EPROTO);
	}

	DTRACE_IO2(recv, vio_dring_msg_t, dring_msg, vdc_t *, vdcp);
	DMSG(vdcp, 1, ": start %d end %d\n", start, end);
	ASSERT(start == end);

	ldep = &vdcp->local_dring[idx];

	DMSG(vdcp, 1, ": state 0x%x - cb_type 0x%x\n",
		ldep->dep->hdr.dstate, ldep->cb_type);

	if (ldep->dep->hdr.dstate == VIO_DESC_DONE) {
		struct buf *bufp;

		switch (ldep->cb_type) {
		case CB_SYNC:
			ASSERT(vdcp->sync_op_pending);

			status = vdc_depopulate_descriptor(vdcp, idx);
			vdcp->sync_op_status = status;
			vdcp->sync_op_pending = B_FALSE;
			cv_signal(&vdcp->sync_pending_cv);
			break;

		case CB_STRATEGY:
			bufp = ldep->cb_arg;
			ASSERT(bufp != NULL);
			status = ldep->dep->payload.status; /* Future:ntoh */
			if (status != 0) {
				DMSG(vdcp, 1, "strategy status=%d\n", status);
				bioerror(bufp, status);
			}
			status = vdc_depopulate_descriptor(vdcp, idx);
			biodone(bufp);
			break;

		default:
			ASSERT(0);
		}
	}

	/* let the arrival signal propogate */
	mutex_exit(&vdcp->lock);

	/* probe gives the count of how many entries were processed */
	DTRACE_IO2(processed, int, 1, vdc_t *, vdcp);

	return (0);
}

/*
 * Function:
 *	vdc_process_err_msg()
 *
 * NOTE: No error messages are used as part of the vDisk protocol
 */
static int
vdc_process_err_msg(vdc_t *vdc, vio_msg_t msg)
{
	_NOTE(ARGUNUSED(vdc))
	_NOTE(ARGUNUSED(msg))

	ASSERT(msg.tag.vio_msgtype == VIO_TYPE_ERR);
	DMSG(vdc, 1, "[%d] Got an ERR msg", vdc->instance);

	return (ENOTSUP);
}

/*
 * Function:
 *	vdc_handle_ver_msg()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *	ver_msg	- LDC message sent by vDisk server
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_handle_ver_msg(vdc_t *vdc, vio_ver_msg_t *ver_msg)
{
	int status = 0;

	ASSERT(vdc != NULL);
	ASSERT(mutex_owned(&vdc->lock));

	if (ver_msg->tag.vio_subtype_env != VIO_VER_INFO) {
		return (EPROTO);
	}

	if (ver_msg->dev_class != VDEV_DISK_SERVER) {
		return (EINVAL);
	}

	switch (ver_msg->tag.vio_subtype) {
	case VIO_SUBTYPE_ACK:
		/*
		 * We check to see if the version returned is indeed supported
		 * (The server may have also adjusted the minor number downwards
		 * and if so 'ver_msg' will contain the actual version agreed)
		 */
		if (vdc_is_supported_version(ver_msg)) {
			vdc->ver.major = ver_msg->ver_major;
			vdc->ver.minor = ver_msg->ver_minor;
			ASSERT(vdc->ver.major > 0);
		} else {
			status = EPROTO;
		}
		break;

	case VIO_SUBTYPE_NACK:
		/*
		 * call vdc_is_supported_version() which will return the next
		 * supported version (if any) in 'ver_msg'
		 */
		(void) vdc_is_supported_version(ver_msg);
		if (ver_msg->ver_major > 0) {
			size_t len = sizeof (*ver_msg);

			ASSERT(vdc->ver.major > 0);

			/* reset the necessary fields and resend */
			ver_msg->tag.vio_subtype = VIO_SUBTYPE_INFO;
			ver_msg->dev_class = VDEV_DISK;

			status = vdc_send(vdc, (caddr_t)ver_msg, &len);
			DMSG(vdc, 0, "[%d] Resend VER info (LDC status = %d)\n",
					vdc->instance, status);
			if (len != sizeof (*ver_msg))
				status = EBADMSG;
		} else {
			DMSG(vdc, 0, "[%d] No common version with "
					"vDisk server", vdc->instance);
			status = ENOTSUP;
		}

		break;
	case VIO_SUBTYPE_INFO:
		/*
		 * Handle the case where vds starts handshake
		 * (for now only vdc is the instigatior)
		 */
		status = ENOTSUP;
		break;

	default:
		status = EINVAL;
		break;
	}

	return (status);
}

/*
 * Function:
 *	vdc_handle_attr_msg()
 *
 * Description:
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *	attr_msg	- LDC message sent by vDisk server
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_handle_attr_msg(vdc_t *vdc, vd_attr_msg_t *attr_msg)
{
	int status = 0;

	ASSERT(vdc != NULL);
	ASSERT(mutex_owned(&vdc->lock));

	if (attr_msg->tag.vio_subtype_env != VIO_ATTR_INFO) {
		return (EPROTO);
	}

	switch (attr_msg->tag.vio_subtype) {
	case VIO_SUBTYPE_ACK:
		/*
		 * We now verify the attributes sent by vds.
		 */
		vdc->vdisk_size = attr_msg->vdisk_size;
		vdc->vdisk_type = attr_msg->vdisk_type;

		DMSG(vdc, 0, "[%d] max_xfer_sz: sent %lx acked %lx\n",
			vdc->instance, vdc->max_xfer_sz, attr_msg->max_xfer_sz);
		DMSG(vdc, 0, "[%d] vdisk_block_size: sent %lx acked %x\n",
			vdc->instance, vdc->block_size,
			attr_msg->vdisk_block_size);

		/*
		 * We don't know at compile time what the vDisk server will
		 * think are good values but we apply an large (arbitrary)
		 * upper bound to prevent memory exhaustion in vdc if it was
		 * allocating a DRing based of huge values sent by the server.
		 * We probably will never exceed this except if the message
		 * was garbage.
		 */
		if ((attr_msg->max_xfer_sz * attr_msg->vdisk_block_size) <=
				(PAGESIZE * DEV_BSIZE)) {
			vdc->max_xfer_sz = attr_msg->max_xfer_sz;
			vdc->block_size = attr_msg->vdisk_block_size;
		} else {
			DMSG(vdc, 0, "[%d] vds block transfer size too big;"
				" using max supported by vdc", vdc->instance);
		}

		if ((attr_msg->xfer_mode != VIO_DRING_MODE) ||
		    (attr_msg->vdisk_size > INT64_MAX) ||
		    (attr_msg->vdisk_type > VD_DISK_TYPE_DISK)) {
			DMSG(vdc, 0, "[%d] Invalid attributes from vds",
					vdc->instance);
			status = EINVAL;
			break;
		}

		break;

	case VIO_SUBTYPE_NACK:
		/*
		 * vds could not handle the attributes we sent so we
		 * stop negotiating.
		 */
		status = EPROTO;
		break;

	case VIO_SUBTYPE_INFO:
		/*
		 * Handle the case where vds starts the handshake
		 * (for now; vdc is the only supported instigatior)
		 */
		status = ENOTSUP;
		break;

	default:
		status = ENOTSUP;
		break;
	}

	return (status);
}

/*
 * Function:
 *	vdc_handle_dring_reg_msg()
 *
 * Description:
 *
 * Arguments:
 *	vdc		- soft state pointer for this instance of the driver.
 *	dring_msg	- LDC message sent by vDisk server
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_handle_dring_reg_msg(vdc_t *vdc, vio_dring_reg_msg_t *dring_msg)
{
	int		status = 0;

	ASSERT(vdc != NULL);
	ASSERT(mutex_owned(&vdc->lock));

	if (dring_msg->tag.vio_subtype_env != VIO_DRING_REG) {
		return (EPROTO);
	}

	switch (dring_msg->tag.vio_subtype) {
	case VIO_SUBTYPE_ACK:
		/* save the received dring_ident */
		vdc->dring_ident = dring_msg->dring_ident;
		DMSG(vdc, 0, "[%d] Received dring ident=0x%lx\n",
			vdc->instance, vdc->dring_ident);
		break;

	case VIO_SUBTYPE_NACK:
		/*
		 * vds could not handle the DRing info we sent so we
		 * stop negotiating.
		 */
		DMSG(vdc, 0, "[%d] server could not register DRing\n",
		    vdc->instance);
		status = EPROTO;
		break;

	case VIO_SUBTYPE_INFO:
		/*
		 * Handle the case where vds starts handshake
		 * (for now only vdc is the instigatior)
		 */
		status = ENOTSUP;
		break;
	default:
		status = ENOTSUP;
	}

	return (status);
}

/*
 * Function:
 *	vdc_verify_seq_num()
 *
 * Description:
 *	This functions verifies that the sequence number sent back by the vDisk
 *	server with the latest message is what is expected (i.e. it is greater
 *	than the last seq num sent by the vDisk server and less than or equal
 *	to the last seq num generated by vdc).
 *
 *	It then checks the request ID to see if any requests need processing
 *	in the DRing.
 *
 * Arguments:
 *	vdc		- soft state pointer for this instance of the driver.
 *	dring_msg	- pointer to the LDC message sent by vds
 *
 * Return Code:
 *	VDC_SEQ_NUM_TODO	- Message needs to be processed
 *	VDC_SEQ_NUM_SKIP	- Message has already been processed
 *	VDC_SEQ_NUM_INVALID	- The seq numbers are so out of sync,
 *				  vdc cannot deal with them
 */
static int
vdc_verify_seq_num(vdc_t *vdc, vio_dring_msg_t *dring_msg)
{
	ASSERT(vdc != NULL);
	ASSERT(dring_msg != NULL);
	ASSERT(mutex_owned(&vdc->lock));

	/*
	 * Check to see if the messages were responded to in the correct
	 * order by vds.
	 */
	if ((dring_msg->seq_num <= vdc->seq_num_reply) ||
	    (dring_msg->seq_num > vdc->seq_num)) {
		DMSG(vdc, 0, "?[%d] Bogus sequence_number %lu: "
			"%lu > expected <= %lu (last proc req %lu sent %lu)\n",
				vdc->instance, dring_msg->seq_num,
				vdc->seq_num_reply, vdc->seq_num,
				vdc->req_id_proc, vdc->req_id);
		return (VDC_SEQ_NUM_INVALID);
	}
	vdc->seq_num_reply = dring_msg->seq_num;

	if (vdc->req_id_proc < vdc->req_id)
		return (VDC_SEQ_NUM_TODO);
	else
		return (VDC_SEQ_NUM_SKIP);
}


/*
 * Function:
 *	vdc_is_supported_version()
 *
 * Description:
 *	This routine checks if the major/minor version numbers specified in
 *	'ver_msg' are supported. If not it finds the next version that is
 *	in the supported version list 'vdc_version[]' and sets the fields in
 *	'ver_msg' to those values
 *
 * Arguments:
 *	ver_msg	- LDC message sent by vDisk server
 *
 * Return Code:
 *	B_TRUE	- Success
 *	B_FALSE	- Version not supported
 */
static boolean_t
vdc_is_supported_version(vio_ver_msg_t *ver_msg)
{
	int vdc_num_versions = sizeof (vdc_version) / sizeof (vdc_version[0]);

	for (int i = 0; i < vdc_num_versions; i++) {
		ASSERT(vdc_version[i].major > 0);
		ASSERT((i == 0) ||
		    (vdc_version[i].major < vdc_version[i-1].major));

		/*
		 * If the major versions match, adjust the minor version, if
		 * necessary, down to the highest value supported by this
		 * client. The server should support all minor versions lower
		 * than the value it sent
		 */
		if (ver_msg->ver_major == vdc_version[i].major) {
			if (ver_msg->ver_minor > vdc_version[i].minor) {
				DMSGX(0,
				    "Adjusting minor version from %u to %u",
				    ver_msg->ver_minor, vdc_version[i].minor);
				ver_msg->ver_minor = vdc_version[i].minor;
			}
			return (B_TRUE);
		}

		/*
		 * If the message contains a higher major version number, set
		 * the message's major/minor versions to the current values
		 * and return false, so this message will get resent with
		 * these values, and the server will potentially try again
		 * with the same or a lower version
		 */
		if (ver_msg->ver_major > vdc_version[i].major) {
			ver_msg->ver_major = vdc_version[i].major;
			ver_msg->ver_minor = vdc_version[i].minor;
			DMSGX(0, "Suggesting major/minor (0x%x/0x%x)\n",
				ver_msg->ver_major, ver_msg->ver_minor);

			return (B_FALSE);
		}

		/*
		 * Otherwise, the message's major version is less than the
		 * current major version, so continue the loop to the next
		 * (lower) supported version
		 */
	}

	/*
	 * No common version was found; "ground" the version pair in the
	 * message to terminate negotiation
	 */
	ver_msg->ver_major = 0;
	ver_msg->ver_minor = 0;

	return (B_FALSE);
}
/* -------------------------------------------------------------------------- */

/*
 * DKIO(7) support
 */

typedef struct vdc_dk_arg {
	struct dk_callback	dkc;
	int			mode;
	dev_t			dev;
	vdc_t			*vdc;
} vdc_dk_arg_t;

/*
 * Function:
 * 	vdc_dkio_flush_cb()
 *
 * Description:
 *	This routine is a callback for DKIOCFLUSHWRITECACHE which can be called
 *	by kernel code.
 *
 * Arguments:
 *	arg	- a pointer to a vdc_dk_arg_t structure.
 */
void
vdc_dkio_flush_cb(void *arg)
{
	struct vdc_dk_arg	*dk_arg = (struct vdc_dk_arg *)arg;
	struct dk_callback	*dkc = NULL;
	vdc_t			*vdc = NULL;
	int			rv;

	if (dk_arg == NULL) {
		cmn_err(CE_NOTE, "?[Unk] DKIOCFLUSHWRITECACHE arg is NULL\n");
		return;
	}
	dkc = &dk_arg->dkc;
	vdc = dk_arg->vdc;
	ASSERT(vdc != NULL);

	rv = vdc_do_sync_op(vdc, VD_OP_FLUSH, NULL, 0,
	    VDCPART(dk_arg->dev), 0, CB_SYNC, 0, VIO_both_dir);
	if (rv != 0) {
		DMSG(vdc, 0, "[%d] DKIOCFLUSHWRITECACHE failed %d : model %x\n",
			vdc->instance, rv,
			ddi_model_convert_from(dk_arg->mode & FMODELS));
	}

	/*
	 * Trigger the call back to notify the caller the the ioctl call has
	 * been completed.
	 */
	if ((dk_arg->mode & FKIOCTL) &&
	    (dkc != NULL) &&
	    (dkc->dkc_callback != NULL)) {
		ASSERT(dkc->dkc_cookie != NULL);
		(*dkc->dkc_callback)(dkc->dkc_cookie, rv);
	}

	/* Indicate that one less DKIO write flush is outstanding */
	mutex_enter(&vdc->lock);
	vdc->dkio_flush_pending--;
	ASSERT(vdc->dkio_flush_pending >= 0);
	mutex_exit(&vdc->lock);

	/* free the mem that was allocated when the callback was dispatched */
	kmem_free(arg, sizeof (vdc_dk_arg_t));
}

/*
 * This structure is used in the DKIO(7I) array below.
 */
typedef struct vdc_dk_ioctl {
	uint8_t		op;		/* VD_OP_XXX value */
	int		cmd;		/* Solaris ioctl operation number */
	size_t		nbytes;		/* size of structure to be copied */

	/* function to convert between vDisk and Solaris structure formats */
	int	(*convert)(vdc_t *vdc, void *vd_buf, void *ioctl_arg,
	    int mode, int dir);
} vdc_dk_ioctl_t;

/*
 * Subset of DKIO(7I) operations currently supported
 */
static vdc_dk_ioctl_t	dk_ioctl[] = {
	{VD_OP_FLUSH,		DKIOCFLUSHWRITECACHE,	sizeof (int),
		vdc_null_copy_func},
	{VD_OP_GET_WCE,		DKIOCGETWCE,		sizeof (int),
		vdc_get_wce_convert},
	{VD_OP_SET_WCE,		DKIOCSETWCE,		sizeof (int),
		vdc_set_wce_convert},
	{VD_OP_GET_VTOC,	DKIOCGVTOC,		sizeof (vd_vtoc_t),
		vdc_get_vtoc_convert},
	{VD_OP_SET_VTOC,	DKIOCSVTOC,		sizeof (vd_vtoc_t),
		vdc_set_vtoc_convert},
	{VD_OP_GET_DISKGEOM,	DKIOCGGEOM,		sizeof (vd_geom_t),
		vdc_get_geom_convert},
	{VD_OP_GET_DISKGEOM,	DKIOCG_PHYGEOM,		sizeof (vd_geom_t),
		vdc_get_geom_convert},
	{VD_OP_GET_DISKGEOM, 	DKIOCG_VIRTGEOM,	sizeof (vd_geom_t),
		vdc_get_geom_convert},
	{VD_OP_SET_DISKGEOM,	DKIOCSGEOM,		sizeof (vd_geom_t),
		vdc_set_geom_convert},
	{VD_OP_GET_EFI,		DKIOCGETEFI,		0,
		vdc_get_efi_convert},
	{VD_OP_SET_EFI,		DKIOCSETEFI,		0,
		vdc_set_efi_convert},

	/*
	 * These particular ioctls are not sent to the server - vdc fakes up
	 * the necessary info.
	 */
	{0, DKIOCINFO, sizeof (struct dk_cinfo), vdc_null_copy_func},
	{0, DKIOCGMEDIAINFO, sizeof (struct dk_minfo), vdc_null_copy_func},
	{0, USCSICMD,	sizeof (struct uscsi_cmd), vdc_null_copy_func},
	{0, DKIOCREMOVABLE, 0, vdc_null_copy_func},
	{0, CDROMREADOFFSET, 0, vdc_null_copy_func}
};

/*
 * Function:
 *	vd_process_ioctl()
 *
 * Description:
 *	This routine processes disk specific ioctl calls
 *
 * Arguments:
 *	dev	- the device number
 *	cmd	- the operation [dkio(7I)] to be processed
 *	arg	- pointer to user provided structure
 *		  (contains data to be set or reference parameter for get)
 *	mode	- bit flag, indicating open settings, 32/64 bit type, etc
 *
 * Return Code:
 *	0
 *	EFAULT
 *	ENXIO
 *	EIO
 *	ENOTSUP
 */
static int
vd_process_ioctl(dev_t dev, int cmd, caddr_t arg, int mode)
{
	int		instance = VDCUNIT(dev);
	vdc_t		*vdc = NULL;
	int		rv = -1;
	int		idx = 0;		/* index into dk_ioctl[] */
	size_t		len = 0;		/* #bytes to send to vds */
	size_t		alloc_len = 0;		/* #bytes to allocate mem for */
	caddr_t		mem_p = NULL;
	size_t		nioctls = (sizeof (dk_ioctl)) / (sizeof (dk_ioctl[0]));
	struct vtoc	vtoc_saved;
	vdc_dk_ioctl_t	*iop;

	vdc = ddi_get_soft_state(vdc_state, instance);
	if (vdc == NULL) {
		cmn_err(CE_NOTE, "![%d] Could not get soft state structure",
		    instance);
		return (ENXIO);
	}

	DMSG(vdc, 0, "[%d] Processing ioctl(%x) for dev %lx : model %x\n",
		instance, cmd, dev, ddi_model_convert_from(mode & FMODELS));

	/*
	 * Validate the ioctl operation to be performed.
	 *
	 * If we have looped through the array without finding a match then we
	 * don't support this ioctl.
	 */
	for (idx = 0; idx < nioctls; idx++) {
		if (cmd == dk_ioctl[idx].cmd)
			break;
	}

	if (idx >= nioctls) {
		DMSG(vdc, 0, "[%d] Unsupported ioctl (0x%x)\n",
		    vdc->instance, cmd);
		return (ENOTSUP);
	}

	iop = &(dk_ioctl[idx]);

	if (cmd == DKIOCGETEFI || cmd == DKIOCSETEFI) {
		/* size is not fixed for EFI ioctls, it depends on ioctl arg */
		dk_efi_t	dk_efi;

		rv = ddi_copyin(arg, &dk_efi, sizeof (dk_efi_t), mode);
		if (rv != 0)
			return (EFAULT);

		len = sizeof (vd_efi_t) - 1 + dk_efi.dki_length;
	} else {
		len = iop->nbytes;
	}

	/*
	 * Deal with the ioctls which the server does not provide. vdc can
	 * fake these up and return immediately
	 */
	switch (cmd) {
	case CDROMREADOFFSET:
	case DKIOCREMOVABLE:
	case USCSICMD:
		return (ENOTTY);

	case DKIOCINFO:
		{
			struct dk_cinfo	cinfo;
			if (vdc->cinfo == NULL)
				return (ENXIO);

			bcopy(vdc->cinfo, &cinfo, sizeof (struct dk_cinfo));
			cinfo.dki_partition = VDCPART(dev);

			rv = ddi_copyout(&cinfo, (void *)arg,
					sizeof (struct dk_cinfo), mode);
			if (rv != 0)
				return (EFAULT);

			return (0);
		}

	case DKIOCGMEDIAINFO:
		{
			if (vdc->minfo == NULL)
				return (ENXIO);

			rv = ddi_copyout(vdc->minfo, (void *)arg,
					sizeof (struct dk_minfo), mode);
			if (rv != 0)
				return (EFAULT);

			return (0);
		}

	case DKIOCFLUSHWRITECACHE:
		{
			struct dk_callback *dkc = (struct dk_callback *)arg;
			vdc_dk_arg_t	*dkarg = NULL;

			DMSG(vdc, 1, "[%d] Flush W$: mode %x\n",
			    instance, mode);

			/*
			 * If the backing device is not a 'real' disk then the
			 * W$ operation request to the vDisk server will fail
			 * so we might as well save the cycles and return now.
			 */
			if (vdc->vdisk_type != VD_DISK_TYPE_DISK)
				return (ENOTTY);

			/*
			 * If arg is NULL, then there is no callback function
			 * registered and the call operates synchronously; we
			 * break and continue with the rest of the function and
			 * wait for vds to return (i.e. after the request to
			 * vds returns successfully, all writes completed prior
			 * to the ioctl will have been flushed from the disk
			 * write cache to persistent media.
			 *
			 * If a callback function is registered, we dispatch
			 * the request on a task queue and return immediately.
			 * The callback will deal with informing the calling
			 * thread that the flush request is completed.
			 */
			if (dkc == NULL)
				break;

			dkarg = kmem_zalloc(sizeof (vdc_dk_arg_t), KM_SLEEP);

			dkarg->mode = mode;
			dkarg->dev = dev;
			bcopy(dkc, &dkarg->dkc, sizeof (*dkc));

			mutex_enter(&vdc->lock);
			vdc->dkio_flush_pending++;
			dkarg->vdc = vdc;
			mutex_exit(&vdc->lock);

			/* put the request on a task queue */
			rv = taskq_dispatch(system_taskq, vdc_dkio_flush_cb,
				(void *)dkarg, DDI_SLEEP);
			if (rv == NULL) {
				/* clean up if dispatch fails */
				mutex_enter(&vdc->lock);
				vdc->dkio_flush_pending--;
				kmem_free(dkarg, sizeof (vdc_dk_arg_t));
			}

			return (rv == NULL ? ENOMEM : 0);
		}
	}

	/* catch programming error in vdc - should be a VD_OP_XXX ioctl */
	ASSERT(iop->op != 0);

	/* LDC requires that the memory being mapped is 8-byte aligned */
	alloc_len = P2ROUNDUP(len, sizeof (uint64_t));
	DMSG(vdc, 1, "[%d] struct size %ld alloc %ld\n",
	    instance, len, alloc_len);

	ASSERT(alloc_len != 0);	/* sanity check */
	mem_p = kmem_zalloc(alloc_len, KM_SLEEP);

	if (cmd == DKIOCSVTOC) {
		/*
		 * Save a copy of the current VTOC so that we can roll back
		 * if the setting of the new VTOC fails.
		 */
		bcopy(vdc->vtoc, &vtoc_saved, sizeof (struct vtoc));
	}

	/*
	 * Call the conversion function for this ioctl whhich if necessary
	 * converts from the Solaris format to the format ARC'ed
	 * as part of the vDisk protocol (FWARC 2006/195)
	 */
	ASSERT(iop->convert != NULL);
	rv = (iop->convert)(vdc, arg, mem_p, mode, VD_COPYIN);
	if (rv != 0) {
		DMSG(vdc, 0, "[%d] convert func returned %d for ioctl 0x%x\n",
				instance, rv, cmd);
		if (mem_p != NULL)
			kmem_free(mem_p, alloc_len);
		return (rv);
	}

	/*
	 * send request to vds to service the ioctl.
	 */
	rv = vdc_do_sync_op(vdc, iop->op, mem_p, alloc_len,
	    VDCPART(dev), 0, CB_SYNC, (void *)(uint64_t)mode,
	    VIO_both_dir);

	if (rv != 0) {
		/*
		 * This is not necessarily an error. The ioctl could
		 * be returning a value such as ENOTTY to indicate
		 * that the ioctl is not applicable.
		 */
		DMSG(vdc, 0, "[%d] vds returned %d for ioctl 0x%x\n",
			instance, rv, cmd);
		if (mem_p != NULL)
			kmem_free(mem_p, alloc_len);

		if (cmd == DKIOCSVTOC) {
			/* update of the VTOC has failed, roll back */
			bcopy(&vtoc_saved, vdc->vtoc, sizeof (struct vtoc));
		}

		return (rv);
	}

	if (cmd == DKIOCSVTOC) {
		/*
		 * The VTOC has been changed. We need to update the device
		 * nodes to handle the case where an EFI label has been
		 * changed to a VTOC label. We also try and update the device
		 * node properties. Failing to set the properties should
		 * not cause an error to be return the caller though.
		 */
		vdc->vdisk_label = VD_DISK_LABEL_VTOC;
		(void) vdc_create_device_nodes_vtoc(vdc);

		if (vdc_create_device_nodes_props(vdc)) {
			DMSG(vdc, 0, "![%d] Failed to update device nodes"
			    " properties", vdc->instance);
		}

	} else if (cmd == DKIOCSETEFI) {
		/*
		 * The EFI has been changed. We need to update the device
		 * nodes to handle the case where a VTOC label has been
		 * changed to an EFI label. We also try and update the device
		 * node properties. Failing to set the properties should
		 * not cause an error to be return the caller though.
		 */
		struct dk_gpt *efi;
		size_t efi_len;

		vdc->vdisk_label = VD_DISK_LABEL_EFI;
		(void) vdc_create_device_nodes_efi(vdc);

		rv = vdc_efi_alloc_and_read(dev, &efi, &efi_len);

		if (rv == 0) {
			vdc_store_efi(vdc, efi);
			rv = vdc_create_device_nodes_props(vdc);
			vd_efi_free(efi, efi_len);
		}

		if (rv) {
			DMSG(vdc, 0, "![%d] Failed to update device nodes"
			    " properties", vdc->instance);
		}
	}

	/*
	 * Call the conversion function (if it exists) for this ioctl
	 * which converts from the format ARC'ed as part of the vDisk
	 * protocol (FWARC 2006/195) back to a format understood by
	 * the rest of Solaris.
	 */
	rv = (iop->convert)(vdc, mem_p, arg, mode, VD_COPYOUT);
	if (rv != 0) {
		DMSG(vdc, 0, "[%d] convert func returned %d for ioctl 0x%x\n",
				instance, rv, cmd);
		if (mem_p != NULL)
			kmem_free(mem_p, alloc_len);
		return (rv);
	}

	if (mem_p != NULL)
		kmem_free(mem_p, alloc_len);

	return (rv);
}

/*
 * Function:
 *
 * Description:
 *	This is an empty conversion function used by ioctl calls which
 *	do not need to convert the data being passed in/out to userland
 */
static int
vdc_null_copy_func(vdc_t *vdc, void *from, void *to, int mode, int dir)
{
	_NOTE(ARGUNUSED(vdc))
	_NOTE(ARGUNUSED(from))
	_NOTE(ARGUNUSED(to))
	_NOTE(ARGUNUSED(mode))
	_NOTE(ARGUNUSED(dir))

	return (0);
}

static int
vdc_get_wce_convert(vdc_t *vdc, void *from, void *to,
    int mode, int dir)
{
	_NOTE(ARGUNUSED(vdc))

	if (dir == VD_COPYIN)
		return (0);		/* nothing to do */

	if (ddi_copyout(from, to, sizeof (int), mode) != 0)
		return (EFAULT);

	return (0);
}

static int
vdc_set_wce_convert(vdc_t *vdc, void *from, void *to,
    int mode, int dir)
{
	_NOTE(ARGUNUSED(vdc))

	if (dir == VD_COPYOUT)
		return (0);		/* nothing to do */

	if (ddi_copyin(from, to, sizeof (int), mode) != 0)
		return (EFAULT);

	return (0);
}

/*
 * Function:
 *	vdc_get_vtoc_convert()
 *
 * Description:
 *	This routine performs the necessary convertions from the DKIOCGVTOC
 *	Solaris structure to the format defined in FWARC 2006/195.
 *
 *	In the struct vtoc definition, the timestamp field is marked as not
 *	supported so it is not part of vDisk protocol (FWARC 2006/195).
 *	However SVM uses that field to check it can write into the VTOC,
 *	so we fake up the info of that field.
 *
 * Arguments:
 *	vdc	- the vDisk client
 *	from	- the buffer containing the data to be copied from
 *	to	- the buffer to be copied to
 *	mode	- flags passed to ioctl() call
 *	dir	- the "direction" of the copy - VD_COPYIN or VD_COPYOUT
 *
 * Return Code:
 *	0	- Success
 *	ENXIO	- incorrect buffer passed in.
 *	EFAULT	- ddi_copyout routine encountered an error.
 */
static int
vdc_get_vtoc_convert(vdc_t *vdc, void *from, void *to, int mode, int dir)
{
	int		i;
	void		*tmp_mem = NULL;
	void		*tmp_memp;
	struct vtoc	vt;
	struct vtoc32	vt32;
	int		copy_len = 0;
	int		rv = 0;

	if (dir != VD_COPYOUT)
		return (0);	/* nothing to do */

	if ((from == NULL) || (to == NULL))
		return (ENXIO);

	if (ddi_model_convert_from(mode & FMODELS) == DDI_MODEL_ILP32)
		copy_len = sizeof (struct vtoc32);
	else
		copy_len = sizeof (struct vtoc);

	tmp_mem = kmem_alloc(copy_len, KM_SLEEP);

	VD_VTOC2VTOC((vd_vtoc_t *)from, &vt);

	/* fake the VTOC timestamp field */
	for (i = 0; i < V_NUMPAR; i++) {
		vt.timestamp[i] = vdc->vtoc->timestamp[i];
	}

	if (ddi_model_convert_from(mode & FMODELS) == DDI_MODEL_ILP32) {
		vtoctovtoc32(vt, vt32);
		tmp_memp = &vt32;
	} else {
		tmp_memp = &vt;
	}
	rv = ddi_copyout(tmp_memp, to, copy_len, mode);
	if (rv != 0)
		rv = EFAULT;

	kmem_free(tmp_mem, copy_len);
	return (rv);
}

/*
 * Function:
 *	vdc_set_vtoc_convert()
 *
 * Description:
 *	This routine performs the necessary convertions from the DKIOCSVTOC
 *	Solaris structure to the format defined in FWARC 2006/195.
 *
 * Arguments:
 *	vdc	- the vDisk client
 *	from	- Buffer with data
 *	to	- Buffer where data is to be copied to
 *	mode	- flags passed to ioctl
 *	dir	- direction of copy (in or out)
 *
 * Return Code:
 *	0	- Success
 *	ENXIO	- Invalid buffer passed in
 *	EFAULT	- ddi_copyin of data failed
 */
static int
vdc_set_vtoc_convert(vdc_t *vdc, void *from, void *to, int mode, int dir)
{
	void		*tmp_mem = NULL;
	struct vtoc	vt;
	struct vtoc	*vtp = &vt;
	vd_vtoc_t	vtvd;
	int		copy_len = 0;
	int		rv = 0;

	if (dir != VD_COPYIN)
		return (0);	/* nothing to do */

	if ((from == NULL) || (to == NULL))
		return (ENXIO);

	if (ddi_model_convert_from(mode & FMODELS) == DDI_MODEL_ILP32)
		copy_len = sizeof (struct vtoc32);
	else
		copy_len = sizeof (struct vtoc);

	tmp_mem = kmem_alloc(copy_len, KM_SLEEP);

	rv = ddi_copyin(from, tmp_mem, copy_len, mode);
	if (rv != 0) {
		kmem_free(tmp_mem, copy_len);
		return (EFAULT);
	}

	if (ddi_model_convert_from(mode & FMODELS) == DDI_MODEL_ILP32) {
		vtoc32tovtoc((*(struct vtoc32 *)tmp_mem), vt);
	} else {
		vtp = tmp_mem;
	}

	/*
	 * The VTOC is being changed, then vdc needs to update the copy
	 * it saved in the soft state structure.
	 */
	bcopy(vtp, vdc->vtoc, sizeof (struct vtoc));

	VTOC2VD_VTOC(vtp, &vtvd);
	bcopy(&vtvd, to, sizeof (vd_vtoc_t));
	kmem_free(tmp_mem, copy_len);

	return (0);
}

/*
 * Function:
 *	vdc_get_geom_convert()
 *
 * Description:
 *	This routine performs the necessary convertions from the DKIOCGGEOM,
 *	DKIOCG_PHYSGEOM and DKIOG_VIRTGEOM Solaris structures to the format
 *	defined in FWARC 2006/195
 *
 * Arguments:
 *	vdc	- the vDisk client
 *	from	- Buffer with data
 *	to	- Buffer where data is to be copied to
 *	mode	- flags passed to ioctl
 *	dir	- direction of copy (in or out)
 *
 * Return Code:
 *	0	- Success
 *	ENXIO	- Invalid buffer passed in
 *	EFAULT	- ddi_copyout of data failed
 */
static int
vdc_get_geom_convert(vdc_t *vdc, void *from, void *to, int mode, int dir)
{
	_NOTE(ARGUNUSED(vdc))

	struct dk_geom	geom;
	int	copy_len = sizeof (struct dk_geom);
	int	rv = 0;

	if (dir != VD_COPYOUT)
		return (0);	/* nothing to do */

	if ((from == NULL) || (to == NULL))
		return (ENXIO);

	VD_GEOM2DK_GEOM((vd_geom_t *)from, &geom);
	rv = ddi_copyout(&geom, to, copy_len, mode);
	if (rv != 0)
		rv = EFAULT;

	return (rv);
}

/*
 * Function:
 *	vdc_set_geom_convert()
 *
 * Description:
 *	This routine performs the necessary convertions from the DKIOCSGEOM
 *	Solaris structure to the format defined in FWARC 2006/195.
 *
 * Arguments:
 *	vdc	- the vDisk client
 *	from	- Buffer with data
 *	to	- Buffer where data is to be copied to
 *	mode	- flags passed to ioctl
 *	dir	- direction of copy (in or out)
 *
 * Return Code:
 *	0	- Success
 *	ENXIO	- Invalid buffer passed in
 *	EFAULT	- ddi_copyin of data failed
 */
static int
vdc_set_geom_convert(vdc_t *vdc, void *from, void *to, int mode, int dir)
{
	_NOTE(ARGUNUSED(vdc))

	vd_geom_t	vdgeom;
	void		*tmp_mem = NULL;
	int		copy_len = sizeof (struct dk_geom);
	int		rv = 0;

	if (dir != VD_COPYIN)
		return (0);	/* nothing to do */

	if ((from == NULL) || (to == NULL))
		return (ENXIO);

	tmp_mem = kmem_alloc(copy_len, KM_SLEEP);

	rv = ddi_copyin(from, tmp_mem, copy_len, mode);
	if (rv != 0) {
		kmem_free(tmp_mem, copy_len);
		return (EFAULT);
	}
	DK_GEOM2VD_GEOM((struct dk_geom *)tmp_mem, &vdgeom);
	bcopy(&vdgeom, to, sizeof (vdgeom));
	kmem_free(tmp_mem, copy_len);

	return (0);
}

static int
vdc_get_efi_convert(vdc_t *vdc, void *from, void *to, int mode, int dir)
{
	_NOTE(ARGUNUSED(vdc))

	vd_efi_t	*vd_efi;
	dk_efi_t	dk_efi;
	int		rv = 0;
	void		*uaddr;

	if ((from == NULL) || (to == NULL))
		return (ENXIO);

	if (dir == VD_COPYIN) {

		vd_efi = (vd_efi_t *)to;

		rv = ddi_copyin(from, &dk_efi, sizeof (dk_efi_t), mode);
		if (rv != 0)
			return (EFAULT);

		vd_efi->lba = dk_efi.dki_lba;
		vd_efi->length = dk_efi.dki_length;
		bzero(vd_efi->data, vd_efi->length);

	} else {

		rv = ddi_copyin(to, &dk_efi, sizeof (dk_efi_t), mode);
		if (rv != 0)
			return (EFAULT);

		uaddr = dk_efi.dki_data;

		dk_efi.dki_data = kmem_alloc(dk_efi.dki_length, KM_SLEEP);

		VD_EFI2DK_EFI((vd_efi_t *)from, &dk_efi);

		rv = ddi_copyout(dk_efi.dki_data, uaddr, dk_efi.dki_length,
		    mode);
		if (rv != 0)
			return (EFAULT);

		kmem_free(dk_efi.dki_data, dk_efi.dki_length);
	}

	return (0);
}

static int
vdc_set_efi_convert(vdc_t *vdc, void *from, void *to, int mode, int dir)
{
	_NOTE(ARGUNUSED(vdc))

	dk_efi_t	dk_efi;
	void		*uaddr;

	if (dir == VD_COPYOUT)
		return (0);	/* nothing to do */

	if ((from == NULL) || (to == NULL))
		return (ENXIO);

	if (ddi_copyin(from, &dk_efi, sizeof (dk_efi_t), mode) != 0)
		return (EFAULT);

	uaddr = dk_efi.dki_data;

	dk_efi.dki_data = kmem_alloc(dk_efi.dki_length, KM_SLEEP);

	if (ddi_copyin(uaddr, dk_efi.dki_data, dk_efi.dki_length, mode) != 0)
		return (EFAULT);

	DK_EFI2VD_EFI(&dk_efi, (vd_efi_t *)to);

	kmem_free(dk_efi.dki_data, dk_efi.dki_length);

	return (0);
}

/*
 * Function:
 *	vdc_create_fake_geometry()
 *
 * Description:
 *	This routine fakes up the disk info needed for some DKIO ioctls.
 *		- DKIOCINFO
 *		- DKIOCGMEDIAINFO
 *
 *	[ just like lofi(7D) and ramdisk(7D) ]
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_create_fake_geometry(vdc_t *vdc)
{
	ASSERT(vdc != NULL);

	/*
	 * Check if max_xfer_sz and vdisk_size are valid
	 */
	if (vdc->vdisk_size == 0 || vdc->max_xfer_sz == 0)
		return (EIO);

	/*
	 * DKIOCINFO support
	 */
	vdc->cinfo = kmem_zalloc(sizeof (struct dk_cinfo), KM_SLEEP);

	(void) strcpy(vdc->cinfo->dki_cname, VDC_DRIVER_NAME);
	(void) strcpy(vdc->cinfo->dki_dname, VDC_DRIVER_NAME);
	/* max_xfer_sz is #blocks so we don't need to divide by DEV_BSIZE */
	vdc->cinfo->dki_maxtransfer = vdc->max_xfer_sz;
	vdc->cinfo->dki_ctype = DKC_SCSI_CCS;
	vdc->cinfo->dki_flags = DKI_FMTVOL;
	vdc->cinfo->dki_cnum = 0;
	vdc->cinfo->dki_addr = 0;
	vdc->cinfo->dki_space = 0;
	vdc->cinfo->dki_prio = 0;
	vdc->cinfo->dki_vec = 0;
	vdc->cinfo->dki_unit = vdc->instance;
	vdc->cinfo->dki_slave = 0;
	/*
	 * The partition number will be created on the fly depending on the
	 * actual slice (i.e. minor node) that is used to request the data.
	 */
	vdc->cinfo->dki_partition = 0;

	/*
	 * DKIOCGMEDIAINFO support
	 */
	if (vdc->minfo == NULL)
		vdc->minfo = kmem_zalloc(sizeof (struct dk_minfo), KM_SLEEP);
	vdc->minfo->dki_media_type = DK_FIXED_DISK;
	vdc->minfo->dki_capacity = vdc->vdisk_size;
	vdc->minfo->dki_lbsize = DEV_BSIZE;

	return (0);
}

/*
 * Function:
 *	vdc_setup_disk_layout()
 *
 * Description:
 *	This routine discovers all the necessary details about the "disk"
 *	by requesting the data that is available from the vDisk server and by
 *	faking up the rest of the data.
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- Success
 */
static int
vdc_setup_disk_layout(vdc_t *vdc)
{
	buf_t	*buf;	/* BREAD requests need to be in a buf_t structure */
	dev_t	dev;
	int	slice = 0;
	int	rv, error;

	ASSERT(vdc != NULL);

	if (vdc->vtoc == NULL)
		vdc->vtoc = kmem_zalloc(sizeof (struct vtoc), KM_SLEEP);

	dev = makedevice(ddi_driver_major(vdc->dip),
				VD_MAKE_DEV(vdc->instance, 0));
	rv = vd_process_ioctl(dev, DKIOCGVTOC, (caddr_t)vdc->vtoc, FKIOCTL);

	if (rv && rv != ENOTSUP) {
		DMSG(vdc, 0, "[%d] Failed to get VTOC (err=%d)",
				vdc->instance, rv);
		return (rv);
	}

	/*
	 * The process of attempting to read VTOC will initiate
	 * the handshake and establish a connection. Following
	 * handshake, go ahead and create geometry.
	 */
	error = vdc_create_fake_geometry(vdc);
	if (error != 0) {
		DMSG(vdc, 0, "[%d] Failed to create disk geometry (err%d)",
		    vdc->instance, error);
		return (error);
	}

	if (rv == ENOTSUP) {
		/*
		 * If the device does not support VTOC then we try
		 * to read an EFI label.
		 */
		struct dk_gpt *efi;
		size_t efi_len;

		rv = vdc_efi_alloc_and_read(dev, &efi, &efi_len);

		if (rv) {
			DMSG(vdc, 0, "[%d] Failed to get EFI (err=%d)",
			    vdc->instance, rv);
			return (rv);
		}

		vdc->vdisk_label = VD_DISK_LABEL_EFI;
		vdc_store_efi(vdc, efi);
		vd_efi_free(efi, efi_len);

		return (0);
	}

	vdc->vdisk_label = VD_DISK_LABEL_VTOC;

	/*
	 * FUTURE: This could be default way for reading the VTOC
	 * from the disk as supposed to sending the VD_OP_GET_VTOC
	 * to the server. Currently this is a sanity check.
	 *
	 * find the slice that represents the entire "disk" and use that to
	 * read the disk label. The convention in Solaris is that slice 2
	 * represents the whole disk so we check that it is, otherwise we
	 * default to slice 0
	 */
	if ((vdc->vdisk_type == VD_DISK_TYPE_DISK) &&
	    (vdc->vtoc->v_part[2].p_tag == V_BACKUP)) {
		slice = 2;
	} else {
		slice = 0;
	}

	/*
	 * Read disk label from start of disk
	 */
	vdc->label = kmem_zalloc(DK_LABEL_SIZE, KM_SLEEP);
	buf = kmem_alloc(sizeof (buf_t), KM_SLEEP);
	bioinit(buf);
	buf->b_un.b_addr = (caddr_t)vdc->label;
	buf->b_bcount = DK_LABEL_SIZE;
	buf->b_flags = B_BUSY | B_READ;
	buf->b_dev = dev;
	rv = vdc_send_request(vdc, VD_OP_BREAD, (caddr_t)vdc->label,
	    DK_LABEL_SIZE, slice, 0, CB_STRATEGY, buf, VIO_read_dir);
	if (rv) {
		DMSG(vdc, 1, "[%d] Failed to read disk block 0\n",
		    vdc->instance);
		kmem_free(buf, sizeof (buf_t));
		return (rv);
	}
	rv = biowait(buf);
	biofini(buf);
	kmem_free(buf, sizeof (buf_t));

	return (rv);
}

/*
 * Function:
 *	vdc_setup_devid()
 *
 * Description:
 *	This routine discovers the devid of a vDisk. It requests the devid of
 *	the underlying device from the vDisk server, builds an encapsulated
 *	devid based on the retrieved devid and registers that new devid to
 *	the vDisk.
 *
 * Arguments:
 *	vdc	- soft state pointer for this instance of the device driver.
 *
 * Return Code:
 *	0	- A devid was succesfully registered for the vDisk
 */
static int
vdc_setup_devid(vdc_t *vdc)
{
	int rv;
	vd_devid_t *vd_devid;
	size_t bufsize, bufid_len;

	/*
	 * At first sight, we don't know the size of the devid that the
	 * server will return but this size will be encoded into the
	 * reply. So we do a first request using a default size then we
	 * check if this size was large enough. If not then we do a second
	 * request with the correct size returned by the server. Note that
	 * ldc requires size to be 8-byte aligned.
	 */
	bufsize = P2ROUNDUP(VD_DEVID_SIZE(VD_DEVID_DEFAULT_LEN),
	    sizeof (uint64_t));
	vd_devid = kmem_zalloc(bufsize, KM_SLEEP);
	bufid_len = bufsize - sizeof (vd_efi_t) - 1;

	rv = vdc_do_sync_op(vdc, VD_OP_GET_DEVID, (caddr_t)vd_devid,
	    bufsize, 0, 0, CB_SYNC, 0, VIO_both_dir);

	DMSG(vdc, 2, "sync_op returned %d\n", rv);

	if (rv) {
		kmem_free(vd_devid, bufsize);
		return (rv);
	}

	if (vd_devid->length > bufid_len) {
		/*
		 * The returned devid is larger than the buffer used. Try again
		 * with a buffer with the right size.
		 */
		kmem_free(vd_devid, bufsize);
		bufsize = P2ROUNDUP(VD_DEVID_SIZE(vd_devid->length),
		    sizeof (uint64_t));
		vd_devid = kmem_zalloc(bufsize, KM_SLEEP);
		bufid_len = bufsize - sizeof (vd_efi_t) - 1;

		rv = vdc_do_sync_op(vdc, VD_OP_GET_DEVID,
		    (caddr_t)vd_devid, bufsize, 0, 0, CB_SYNC, 0,
		    VIO_both_dir);

		if (rv) {
			kmem_free(vd_devid, bufsize);
			return (rv);
		}
	}

	/*
	 * The virtual disk should have the same device id as the one associated
	 * with the physical disk it is mapped on, otherwise sharing a disk
	 * between a LDom and a non-LDom may not work (for example for a shared
	 * SVM disk set).
	 *
	 * The DDI framework does not allow creating a device id with any
	 * type so we first create a device id of type DEVID_ENCAP and then
	 * we restore the orignal type of the physical device.
	 */

	DMSG(vdc, 2, ": devid length = %d\n", vd_devid->length);

	/* build an encapsulated devid based on the returned devid */
	if (ddi_devid_init(vdc->dip, DEVID_ENCAP, vd_devid->length,
		vd_devid->id, &vdc->devid) != DDI_SUCCESS) {
		DMSG(vdc, 1, "[%d] Fail to created devid\n", vdc->instance);
		kmem_free(vd_devid, bufsize);
		return (1);
	}

	DEVID_FORMTYPE((impl_devid_t *)vdc->devid, vd_devid->type);

	ASSERT(ddi_devid_valid(vdc->devid) == DDI_SUCCESS);

	kmem_free(vd_devid, bufsize);

	if (ddi_devid_register(vdc->dip, vdc->devid) != DDI_SUCCESS) {
		DMSG(vdc, 1, "[%d] Fail to register devid\n", vdc->instance);
		return (1);
	}

	return (0);
}

static void
vdc_store_efi(vdc_t *vdc, struct dk_gpt *efi)
{
	struct vtoc *vtoc = vdc->vtoc;

	vd_efi_to_vtoc(efi, vtoc);
	if (vdc->vdisk_type == VD_DISK_TYPE_SLICE) {
		/*
		 * vd_efi_to_vtoc() will store information about the EFI Sun
		 * reserved partition (representing the entire disk) into
		 * partition 7. However single-slice device will only have
		 * that single partition and the vdc driver expects to find
		 * information about that partition in slice 0. So we need
		 * to copy information from slice 7 to slice 0.
		 */
		vtoc->v_part[0].p_tag = vtoc->v_part[VD_EFI_WD_SLICE].p_tag;
		vtoc->v_part[0].p_flag = vtoc->v_part[VD_EFI_WD_SLICE].p_flag;
		vtoc->v_part[0].p_start = vtoc->v_part[VD_EFI_WD_SLICE].p_start;
		vtoc->v_part[0].p_size =  vtoc->v_part[VD_EFI_WD_SLICE].p_size;
	}
}