xref: /freebsd/usr.sbin/bhyve/pci_virtio_block.c (revision 7fdf597e96a02165cfe22ff357b857d5fa15ed8a)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause
3  *
4  * Copyright (c) 2011 NetApp, Inc.
5  * All rights reserved.
6  * Copyright 2020-2021 Joyent, Inc.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY NETAPP, INC ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL NETAPP, INC OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  */
29 
30 #include <sys/param.h>
31 #include <sys/linker_set.h>
32 #include <sys/stat.h>
33 #include <sys/uio.h>
34 #include <sys/ioctl.h>
35 #include <sys/disk.h>
36 
37 #include <machine/vmm_snapshot.h>
38 
39 #include <errno.h>
40 #include <fcntl.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <stdint.h>
44 #include <string.h>
45 #include <strings.h>
46 #include <unistd.h>
47 #include <assert.h>
48 #include <pthread.h>
49 #include <md5.h>
50 
51 #include "bhyverun.h"
52 #include "config.h"
53 #include "debug.h"
54 #include "pci_emul.h"
55 #include "virtio.h"
56 #include "block_if.h"
57 
58 #define	VTBLK_BSIZE	512
59 #define	VTBLK_RINGSZ	128
60 
61 _Static_assert(VTBLK_RINGSZ <= BLOCKIF_RING_MAX, "Each ring entry must be able to queue a request");
62 
63 #define	VTBLK_S_OK	0
64 #define	VTBLK_S_IOERR	1
65 #define	VTBLK_S_UNSUPP	2
66 
67 #define	VTBLK_BLK_ID_BYTES	20 + 1
68 
69 /* Capability bits */
70 #define	VTBLK_F_BARRIER		(1 << 0)	/* Does host support barriers? */
71 #define	VTBLK_F_SIZE_MAX	(1 << 1)	/* Indicates maximum segment size */
72 #define	VTBLK_F_SEG_MAX		(1 << 2)	/* Indicates maximum # of segments */
73 #define	VTBLK_F_GEOMETRY	(1 << 4)	/* Legacy geometry available  */
74 #define	VTBLK_F_RO		(1 << 5)	/* Disk is read-only */
75 #define	VTBLK_F_BLK_SIZE	(1 << 6)	/* Block size of disk is available*/
76 #define	VTBLK_F_SCSI		(1 << 7)	/* Supports scsi command passthru */
77 #define	VTBLK_F_FLUSH		(1 << 9)	/* Writeback mode enabled after reset */
78 #define	VTBLK_F_WCE		(1 << 9)	/* Legacy alias for FLUSH */
79 #define	VTBLK_F_TOPOLOGY	(1 << 10)	/* Topology information is available */
80 #define	VTBLK_F_CONFIG_WCE	(1 << 11)	/* Writeback mode available in config */
81 #define	VTBLK_F_MQ		(1 << 12)	/* Multi-Queue */
82 #define	VTBLK_F_DISCARD		(1 << 13)	/* Trim blocks */
83 #define	VTBLK_F_WRITE_ZEROES	(1 << 14)	/* Write zeros */
84 
85 /*
86  * Host capabilities
87  */
88 #define	VTBLK_S_HOSTCAPS      \
89   ( VTBLK_F_SEG_MAX  |						    \
90     VTBLK_F_BLK_SIZE |						    \
91     VTBLK_F_FLUSH    |						    \
92     VTBLK_F_TOPOLOGY |						    \
93     VIRTIO_RING_F_INDIRECT_DESC )	/* indirect descriptors */
94 
95 /*
96  * The current blockif_delete() interface only allows a single delete
97  * request at a time.
98  */
99 #define	VTBLK_MAX_DISCARD_SEG	1
100 
101 /*
102  * An arbitrary limit to prevent excessive latency due to large
103  * delete requests.
104  */
105 #define	VTBLK_MAX_DISCARD_SECT	((16 << 20) / VTBLK_BSIZE)	/* 16 MiB */
106 
107 /*
108  * Config space "registers"
109  */
110 struct vtblk_config {
111 	uint64_t	vbc_capacity;
112 	uint32_t	vbc_size_max;
113 	uint32_t	vbc_seg_max;
114 	struct {
115 		uint16_t cylinders;
116 		uint8_t heads;
117 		uint8_t sectors;
118 	} vbc_geometry;
119 	uint32_t	vbc_blk_size;
120 	struct {
121 		uint8_t physical_block_exp;
122 		uint8_t alignment_offset;
123 		uint16_t min_io_size;
124 		uint32_t opt_io_size;
125 	} vbc_topology;
126 	uint8_t		vbc_writeback;
127 	uint8_t		unused0[1];
128 	uint16_t	num_queues;
129 	uint32_t	max_discard_sectors;
130 	uint32_t	max_discard_seg;
131 	uint32_t	discard_sector_alignment;
132 	uint32_t	max_write_zeroes_sectors;
133 	uint32_t	max_write_zeroes_seg;
134 	uint8_t		write_zeroes_may_unmap;
135 	uint8_t		unused1[3];
136 } __packed;
137 
138 /*
139  * Fixed-size block header
140  */
141 struct virtio_blk_hdr {
142 #define	VBH_OP_READ		0
143 #define	VBH_OP_WRITE		1
144 #define	VBH_OP_SCSI_CMD		2
145 #define	VBH_OP_SCSI_CMD_OUT	3
146 #define	VBH_OP_FLUSH		4
147 #define	VBH_OP_FLUSH_OUT	5
148 #define	VBH_OP_IDENT		8
149 #define	VBH_OP_DISCARD		11
150 #define	VBH_OP_WRITE_ZEROES	13
151 
152 #define	VBH_FLAG_BARRIER	0x80000000	/* OR'ed into vbh_type */
153 	uint32_t	vbh_type;
154 	uint32_t	vbh_ioprio;
155 	uint64_t	vbh_sector;
156 } __packed;
157 
158 /*
159  * Debug printf
160  */
161 static int pci_vtblk_debug;
162 #define	DPRINTF(params) if (pci_vtblk_debug) PRINTLN params
163 #define	WPRINTF(params) PRINTLN params
164 
165 struct pci_vtblk_ioreq {
166 	struct blockif_req		io_req;
167 	struct pci_vtblk_softc		*io_sc;
168 	uint8_t				*io_status;
169 	uint16_t			io_idx;
170 };
171 
172 struct virtio_blk_discard_write_zeroes {
173 	uint64_t	sector;
174 	uint32_t	num_sectors;
175 	struct {
176 		uint32_t unmap:1;
177 		uint32_t reserved:31;
178 	} flags;
179 };
180 
181 /*
182  * Per-device softc
183  */
184 struct pci_vtblk_softc {
185 	struct virtio_softc vbsc_vs;
186 	pthread_mutex_t vsc_mtx;
187 	struct vqueue_info vbsc_vq;
188 	struct vtblk_config vbsc_cfg;
189 	struct virtio_consts vbsc_consts;
190 	struct blockif_ctxt *bc;
191 	char vbsc_ident[VTBLK_BLK_ID_BYTES];
192 	struct pci_vtblk_ioreq vbsc_ios[VTBLK_RINGSZ];
193 };
194 
195 static void pci_vtblk_reset(void *);
196 static void pci_vtblk_notify(void *, struct vqueue_info *);
197 static int pci_vtblk_cfgread(void *, int, int, uint32_t *);
198 static int pci_vtblk_cfgwrite(void *, int, int, uint32_t);
199 #ifdef BHYVE_SNAPSHOT
200 static void pci_vtblk_pause(void *);
201 static void pci_vtblk_resume(void *);
202 static int pci_vtblk_snapshot(void *, struct vm_snapshot_meta *);
203 #endif
204 
205 static struct virtio_consts vtblk_vi_consts = {
206 	.vc_name =	"vtblk",
207 	.vc_nvq =	1,
208 	.vc_cfgsize =	sizeof(struct vtblk_config),
209 	.vc_reset =	pci_vtblk_reset,
210 	.vc_qnotify =	pci_vtblk_notify,
211 	.vc_cfgread =	pci_vtblk_cfgread,
212 	.vc_cfgwrite =	pci_vtblk_cfgwrite,
213 	.vc_apply_features = NULL,
214 	.vc_hv_caps =	VTBLK_S_HOSTCAPS,
215 #ifdef BHYVE_SNAPSHOT
216 	.vc_pause =	pci_vtblk_pause,
217 	.vc_resume =	pci_vtblk_resume,
218 	.vc_snapshot =	pci_vtblk_snapshot,
219 #endif
220 };
221 
222 static void
223 pci_vtblk_reset(void *vsc)
224 {
225 	struct pci_vtblk_softc *sc = vsc;
226 
227 	DPRINTF(("vtblk: device reset requested !"));
228 	vi_reset_dev(&sc->vbsc_vs);
229 }
230 
231 static void
232 pci_vtblk_done_locked(struct pci_vtblk_ioreq *io, int err)
233 {
234 	struct pci_vtblk_softc *sc = io->io_sc;
235 
236 	/* convert errno into a virtio block error return */
237 	if (err == EOPNOTSUPP || err == ENOSYS)
238 		*io->io_status = VTBLK_S_UNSUPP;
239 	else if (err != 0)
240 		*io->io_status = VTBLK_S_IOERR;
241 	else
242 		*io->io_status = VTBLK_S_OK;
243 
244 	/*
245 	 * Return the descriptor back to the host.
246 	 * We wrote 1 byte (our status) to host.
247 	 */
248 	vq_relchain(&sc->vbsc_vq, io->io_idx, 1);
249 	vq_endchains(&sc->vbsc_vq, 0);
250 }
251 
252 #ifdef BHYVE_SNAPSHOT
253 static void
254 pci_vtblk_pause(void *vsc)
255 {
256 	struct pci_vtblk_softc *sc = vsc;
257 
258 	DPRINTF(("vtblk: device pause requested !\n"));
259 	blockif_pause(sc->bc);
260 }
261 
262 static void
263 pci_vtblk_resume(void *vsc)
264 {
265 	struct pci_vtblk_softc *sc = vsc;
266 
267 	DPRINTF(("vtblk: device resume requested !\n"));
268 	blockif_resume(sc->bc);
269 }
270 
271 static int
272 pci_vtblk_snapshot(void *vsc, struct vm_snapshot_meta *meta)
273 {
274 	int ret;
275 	struct pci_vtblk_softc *sc = vsc;
276 
277 	SNAPSHOT_VAR_OR_LEAVE(sc->vbsc_cfg, meta, ret, done);
278 	SNAPSHOT_BUF_OR_LEAVE(sc->vbsc_ident, sizeof(sc->vbsc_ident),
279 			      meta, ret, done);
280 
281 done:
282 	return (ret);
283 }
284 #endif
285 
286 static void
287 pci_vtblk_done(struct blockif_req *br, int err)
288 {
289 	struct pci_vtblk_ioreq *io = br->br_param;
290 	struct pci_vtblk_softc *sc = io->io_sc;
291 
292 	pthread_mutex_lock(&sc->vsc_mtx);
293 	pci_vtblk_done_locked(io, err);
294 	pthread_mutex_unlock(&sc->vsc_mtx);
295 }
296 
297 static void
298 pci_vtblk_proc(struct pci_vtblk_softc *sc, struct vqueue_info *vq)
299 {
300 	struct virtio_blk_hdr *vbh;
301 	struct pci_vtblk_ioreq *io;
302 	int i, n;
303 	int err;
304 	ssize_t iolen;
305 	int writeop, type;
306 	struct vi_req req;
307 	struct iovec iov[BLOCKIF_IOV_MAX + 2];
308 	struct virtio_blk_discard_write_zeroes *discard;
309 
310 	n = vq_getchain(vq, iov, BLOCKIF_IOV_MAX + 2, &req);
311 
312 	/*
313 	 * The first descriptor will be the read-only fixed header,
314 	 * and the last is for status (hence +2 above and below).
315 	 * The remaining iov's are the actual data I/O vectors.
316 	 *
317 	 * XXX - note - this fails on crash dump, which does a
318 	 * VIRTIO_BLK_T_FLUSH with a zero transfer length
319 	 */
320 	assert(n >= 2 && n <= BLOCKIF_IOV_MAX + 2);
321 
322 	io = &sc->vbsc_ios[req.idx];
323 	assert(req.readable != 0);
324 	assert(iov[0].iov_len == sizeof(struct virtio_blk_hdr));
325 	vbh = (struct virtio_blk_hdr *)iov[0].iov_base;
326 	memcpy(&io->io_req.br_iov, &iov[1], sizeof(struct iovec) * (n - 2));
327 	io->io_req.br_iovcnt = n - 2;
328 	io->io_req.br_offset = vbh->vbh_sector * VTBLK_BSIZE;
329 	io->io_status = (uint8_t *)iov[--n].iov_base;
330 	assert(req.writable != 0);
331 	assert(iov[n].iov_len == 1);
332 
333 	/*
334 	 * XXX
335 	 * The guest should not be setting the BARRIER flag because
336 	 * we don't advertise the capability.
337 	 */
338 	type = vbh->vbh_type & ~VBH_FLAG_BARRIER;
339 	writeop = (type == VBH_OP_WRITE || type == VBH_OP_DISCARD);
340 	/*
341 	 * - Write op implies read-only descriptor
342 	 * - Read/ident op implies write-only descriptor
343 	 *
344 	 * By taking away either the read-only fixed header or the write-only
345 	 * status iovec, the following condition should hold true.
346 	 */
347 	assert(n == (writeop ? req.readable : req.writable));
348 
349 	iolen = 0;
350 	for (i = 1; i < n; i++) {
351 		iolen += iov[i].iov_len;
352 	}
353 	io->io_req.br_resid = iolen;
354 
355 	DPRINTF(("virtio-block: %s op, %zd bytes, %d segs, offset %ld",
356 		 writeop ? "write/discard" : "read/ident", iolen, i - 1,
357 		 io->io_req.br_offset));
358 
359 	switch (type) {
360 	case VBH_OP_READ:
361 		err = blockif_read(sc->bc, &io->io_req);
362 		break;
363 	case VBH_OP_WRITE:
364 		err = blockif_write(sc->bc, &io->io_req);
365 		break;
366 	case VBH_OP_DISCARD:
367 		/*
368 		 * We currently only support a single request, if the guest
369 		 * has submitted a request that doesn't conform to the
370 		 * requirements, we return a error.
371 		 */
372 		if (iov[1].iov_len != sizeof (*discard)) {
373 			pci_vtblk_done_locked(io, EINVAL);
374 			return;
375 		}
376 
377 		/* The segments to discard are provided rather than data */
378 		discard = (struct virtio_blk_discard_write_zeroes *)
379 		    iov[1].iov_base;
380 
381 		/*
382 		 * virtio v1.1 5.2.6.2:
383 		 * The device MUST set the status byte to VIRTIO_BLK_S_UNSUPP
384 		 * for discard and write zeroes commands if any unknown flag is
385 		 * set. Furthermore, the device MUST set the status byte to
386 		 * VIRTIO_BLK_S_UNSUPP for discard commands if the unmap flag
387 		 * is set.
388 		 *
389 		 * Currently there are no known flags for a DISCARD request.
390 		 */
391 		if (discard->flags.unmap != 0 || discard->flags.reserved != 0) {
392 			pci_vtblk_done_locked(io, ENOTSUP);
393 			return;
394 		}
395 
396 		/* Make sure the request doesn't exceed our size limit */
397 		if (discard->num_sectors > VTBLK_MAX_DISCARD_SECT) {
398 			pci_vtblk_done_locked(io, EINVAL);
399 			return;
400 		}
401 
402 		io->io_req.br_offset = discard->sector * VTBLK_BSIZE;
403 		io->io_req.br_resid = discard->num_sectors * VTBLK_BSIZE;
404 		err = blockif_delete(sc->bc, &io->io_req);
405 		break;
406 	case VBH_OP_FLUSH:
407 	case VBH_OP_FLUSH_OUT:
408 		err = blockif_flush(sc->bc, &io->io_req);
409 		break;
410 	case VBH_OP_IDENT:
411 		/* Assume a single buffer */
412 		/* S/n equal to buffer is not zero-terminated. */
413 		memset(iov[1].iov_base, 0, iov[1].iov_len);
414 		strncpy(iov[1].iov_base, sc->vbsc_ident,
415 		    MIN(iov[1].iov_len, sizeof(sc->vbsc_ident)));
416 		pci_vtblk_done_locked(io, 0);
417 		return;
418 	default:
419 		pci_vtblk_done_locked(io, EOPNOTSUPP);
420 		return;
421 	}
422 	assert(err == 0);
423 }
424 
425 static void
426 pci_vtblk_notify(void *vsc, struct vqueue_info *vq)
427 {
428 	struct pci_vtblk_softc *sc = vsc;
429 
430 	while (vq_has_descs(vq))
431 		pci_vtblk_proc(sc, vq);
432 }
433 
434 static void
435 pci_vtblk_resized(struct blockif_ctxt *bctxt __unused, void *arg,
436     size_t new_size)
437 {
438 	struct pci_vtblk_softc *sc;
439 
440 	sc = arg;
441 
442 	sc->vbsc_cfg.vbc_capacity = new_size / VTBLK_BSIZE; /* 512-byte units */
443 	vi_interrupt(&sc->vbsc_vs, VIRTIO_PCI_ISR_CONFIG,
444 	    sc->vbsc_vs.vs_msix_cfg_idx);
445 }
446 
447 static int
448 pci_vtblk_init(struct pci_devinst *pi, nvlist_t *nvl)
449 {
450 	char bident[sizeof("XXX:XXX")];
451 	struct blockif_ctxt *bctxt;
452 	const char *path, *serial;
453 	MD5_CTX mdctx;
454 	u_char digest[16];
455 	struct pci_vtblk_softc *sc;
456 	off_t size;
457 	int i, sectsz, sts, sto;
458 
459 	/*
460 	 * The supplied backing file has to exist
461 	 */
462 	snprintf(bident, sizeof(bident), "%u:%u", pi->pi_slot, pi->pi_func);
463 	bctxt = blockif_open(nvl, bident);
464 	if (bctxt == NULL) {
465 		perror("Could not open backing file");
466 		return (1);
467 	}
468 
469 	if (blockif_add_boot_device(pi, bctxt)) {
470 		perror("Invalid boot device");
471 		return (1);
472 	}
473 
474 	size = blockif_size(bctxt);
475 	sectsz = blockif_sectsz(bctxt);
476 	blockif_psectsz(bctxt, &sts, &sto);
477 
478 	sc = calloc(1, sizeof(struct pci_vtblk_softc));
479 	sc->bc = bctxt;
480 	for (i = 0; i < VTBLK_RINGSZ; i++) {
481 		struct pci_vtblk_ioreq *io = &sc->vbsc_ios[i];
482 		io->io_req.br_callback = pci_vtblk_done;
483 		io->io_req.br_param = io;
484 		io->io_sc = sc;
485 		io->io_idx = i;
486 	}
487 
488 	bcopy(&vtblk_vi_consts, &sc->vbsc_consts, sizeof (vtblk_vi_consts));
489 	if (blockif_candelete(sc->bc))
490 		sc->vbsc_consts.vc_hv_caps |= VTBLK_F_DISCARD;
491 
492 	pthread_mutex_init(&sc->vsc_mtx, NULL);
493 
494 	/* init virtio softc and virtqueues */
495 	vi_softc_linkup(&sc->vbsc_vs, &sc->vbsc_consts, sc, pi, &sc->vbsc_vq);
496 	sc->vbsc_vs.vs_mtx = &sc->vsc_mtx;
497 
498 	sc->vbsc_vq.vq_qsize = VTBLK_RINGSZ;
499 	/* sc->vbsc_vq.vq_notify = we have no per-queue notify */
500 
501 	/*
502 	 * If an explicit identifier is not given, create an
503 	 * identifier using parts of the md5 sum of the filename.
504 	 */
505 	bzero(sc->vbsc_ident, VTBLK_BLK_ID_BYTES);
506 	if ((serial = get_config_value_node(nvl, "serial")) != NULL ||
507 	    (serial = get_config_value_node(nvl, "ser")) != NULL) {
508 		strlcpy(sc->vbsc_ident, serial, VTBLK_BLK_ID_BYTES);
509 	} else {
510 		path = get_config_value_node(nvl, "path");
511 		MD5Init(&mdctx);
512 		MD5Update(&mdctx, path, strlen(path));
513 		MD5Final(digest, &mdctx);
514 		snprintf(sc->vbsc_ident, VTBLK_BLK_ID_BYTES,
515 		    "BHYVE-%02X%02X-%02X%02X-%02X%02X",
516 		    digest[0], digest[1], digest[2], digest[3], digest[4],
517 		    digest[5]);
518 	}
519 
520 	/* setup virtio block config space */
521 	sc->vbsc_cfg.vbc_capacity = size / VTBLK_BSIZE; /* 512-byte units */
522 	sc->vbsc_cfg.vbc_size_max = 0;	/* not negotiated */
523 
524 	/*
525 	 * If Linux is presented with a seg_max greater than the virtio queue
526 	 * size, it can stumble into situations where it violates its own
527 	 * invariants and panics.  For safety, we keep seg_max clamped, paying
528 	 * heed to the two extra descriptors needed for the header and status
529 	 * of a request.
530 	 */
531 	sc->vbsc_cfg.vbc_seg_max = MIN(VTBLK_RINGSZ - 2, BLOCKIF_IOV_MAX);
532 	sc->vbsc_cfg.vbc_geometry.cylinders = 0;	/* no geometry */
533 	sc->vbsc_cfg.vbc_geometry.heads = 0;
534 	sc->vbsc_cfg.vbc_geometry.sectors = 0;
535 	sc->vbsc_cfg.vbc_blk_size = sectsz;
536 	sc->vbsc_cfg.vbc_topology.physical_block_exp =
537 	    (sts > sectsz) ? (ffsll(sts / sectsz) - 1) : 0;
538 	sc->vbsc_cfg.vbc_topology.alignment_offset =
539 	    (sto != 0) ? ((sts - sto) / sectsz) : 0;
540 	sc->vbsc_cfg.vbc_topology.min_io_size = 0;
541 	sc->vbsc_cfg.vbc_topology.opt_io_size = 0;
542 	sc->vbsc_cfg.vbc_writeback = 0;
543 	sc->vbsc_cfg.max_discard_sectors = VTBLK_MAX_DISCARD_SECT;
544 	sc->vbsc_cfg.max_discard_seg = VTBLK_MAX_DISCARD_SEG;
545 	sc->vbsc_cfg.discard_sector_alignment = MAX(sectsz, sts) / VTBLK_BSIZE;
546 
547 	/*
548 	 * Should we move some of this into virtio.c?  Could
549 	 * have the device, class, and subdev_0 as fields in
550 	 * the virtio constants structure.
551 	 */
552 	pci_set_cfgdata16(pi, PCIR_DEVICE, VIRTIO_DEV_BLOCK);
553 	pci_set_cfgdata16(pi, PCIR_VENDOR, VIRTIO_VENDOR);
554 	pci_set_cfgdata8(pi, PCIR_CLASS, PCIC_STORAGE);
555 	pci_set_cfgdata16(pi, PCIR_SUBDEV_0, VIRTIO_ID_BLOCK);
556 	pci_set_cfgdata16(pi, PCIR_SUBVEND_0, VIRTIO_VENDOR);
557 
558 	if (vi_intr_init(&sc->vbsc_vs, 1, fbsdrun_virtio_msix())) {
559 		blockif_close(sc->bc);
560 		free(sc);
561 		return (1);
562 	}
563 	vi_set_io_bar(&sc->vbsc_vs, 0);
564 	blockif_register_resize_callback(sc->bc, pci_vtblk_resized, sc);
565 	return (0);
566 }
567 
568 static int
569 pci_vtblk_cfgwrite(void *vsc __unused, int offset, int size __unused,
570     uint32_t value __unused)
571 {
572 
573 	DPRINTF(("vtblk: write to readonly reg %d", offset));
574 	return (1);
575 }
576 
577 static int
578 pci_vtblk_cfgread(void *vsc, int offset, int size, uint32_t *retval)
579 {
580 	struct pci_vtblk_softc *sc = vsc;
581 	void *ptr;
582 
583 	/* our caller has already verified offset and size */
584 	ptr = (uint8_t *)&sc->vbsc_cfg + offset;
585 	memcpy(retval, ptr, size);
586 	return (0);
587 }
588 
589 static const struct pci_devemu pci_de_vblk = {
590 	.pe_emu =	"virtio-blk",
591 	.pe_init =	pci_vtblk_init,
592 	.pe_legacy_config = blockif_legacy_config,
593 	.pe_barwrite =	vi_pci_write,
594 	.pe_barread =	vi_pci_read,
595 #ifdef BHYVE_SNAPSHOT
596 	.pe_snapshot =	vi_pci_snapshot,
597 	.pe_pause =     vi_pci_pause,
598 	.pe_resume =    vi_pci_resume,
599 #endif
600 };
601 PCI_EMUL_SET(pci_de_vblk);
602