xref: /linux/drivers/cxl/pci.c (revision e80a48bade619ec5a92230b3d4ae84bfc2746822)

// SPDX-License-Identifier: GPL-2.0-only
/* Copyright(c) 2020 Intel Corporation. All rights reserved. */
#include <linux/io-64-nonatomic-lo-hi.h>
#include <linux/moduleparam.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/sizes.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/pci.h>
#include <linux/pci-doe.h>
#include <linux/aer.h>
#include <linux/io.h>
#include "cxlmem.h"
#include "cxlpci.h"
#include "cxl.h"
#define CREATE_TRACE_POINTS
#include <trace/events/cxl.h>

/**
 * DOC: cxl pci
 *
 * This implements the PCI exclusive functionality for a CXL device as it is
 * defined by the Compute Express Link specification. CXL devices may surface
 * certain functionality even if it isn't CXL enabled. While this driver is
 * focused around the PCI specific aspects of a CXL device, it binds to the
 * specific CXL memory device class code, and therefore the implementation of
 * cxl_pci is focused around CXL memory devices.
 *
 * The driver has several responsibilities, mainly:
 *  - Create the memX device and register on the CXL bus.
 *  - Enumerate device's register interface and map them.
 *  - Registers nvdimm bridge device with cxl_core.
 *  - Registers a CXL mailbox with cxl_core.
 */

#define cxl_doorbell_busy(cxlds)                                                \
	(readl((cxlds)->regs.mbox + CXLDEV_MBOX_CTRL_OFFSET) &                  \
	 CXLDEV_MBOX_CTRL_DOORBELL)

/* CXL 2.0 - 8.2.8.4 */
#define CXL_MAILBOX_TIMEOUT_MS (2 * HZ)

/*
 * CXL 2.0 ECN "Add Mailbox Ready Time" defines a capability field to
 * dictate how long to wait for the mailbox to become ready. The new
 * field allows the device to tell software the amount of time to wait
 * before mailbox ready. This field per the spec theoretically allows
 * for up to 255 seconds. 255 seconds is unreasonably long, its longer
 * than the maximum SATA port link recovery wait. Default to 60 seconds
 * until someone builds a CXL device that needs more time in practice.
 */
static unsigned short mbox_ready_timeout = 60;
module_param(mbox_ready_timeout, ushort, 0644);
MODULE_PARM_DESC(mbox_ready_timeout, "seconds to wait for mailbox ready");

static int cxl_pci_mbox_wait_for_doorbell(struct cxl_dev_state *cxlds)
{
	const unsigned long start = jiffies;
	unsigned long end = start;

	while (cxl_doorbell_busy(cxlds)) {
		end = jiffies;

		if (time_after(end, start + CXL_MAILBOX_TIMEOUT_MS)) {
			/* Check again in case preempted before timeout test */
			if (!cxl_doorbell_busy(cxlds))
				break;
			return -ETIMEDOUT;
		}
		cpu_relax();
	}

	dev_dbg(cxlds->dev, "Doorbell wait took %dms",
		jiffies_to_msecs(end) - jiffies_to_msecs(start));
	return 0;
}

#define cxl_err(dev, status, msg)                                        \
	dev_err_ratelimited(dev, msg ", device state %s%s\n",                  \
			    status & CXLMDEV_DEV_FATAL ? " fatal" : "",        \
			    status & CXLMDEV_FW_HALT ? " firmware-halt" : "")

#define cxl_cmd_err(dev, cmd, status, msg)                               \
	dev_err_ratelimited(dev, msg " (opcode: %#x), device state %s%s\n",    \
			    (cmd)->opcode,                                     \
			    status & CXLMDEV_DEV_FATAL ? " fatal" : "",        \
			    status & CXLMDEV_FW_HALT ? " firmware-halt" : "")

/**
 * __cxl_pci_mbox_send_cmd() - Execute a mailbox command
 * @cxlds: The device state to communicate with.
 * @mbox_cmd: Command to send to the memory device.
 *
 * Context: Any context. Expects mbox_mutex to be held.
 * Return: -ETIMEDOUT if timeout occurred waiting for completion. 0 on success.
 *         Caller should check the return code in @mbox_cmd to make sure it
 *         succeeded.
 *
 * This is a generic form of the CXL mailbox send command thus only using the
 * registers defined by the mailbox capability ID - CXL 2.0 8.2.8.4. Memory
 * devices, and perhaps other types of CXL devices may have further information
 * available upon error conditions. Driver facilities wishing to send mailbox
 * commands should use the wrapper command.
 *
 * The CXL spec allows for up to two mailboxes. The intention is for the primary
 * mailbox to be OS controlled and the secondary mailbox to be used by system
 * firmware. This allows the OS and firmware to communicate with the device and
 * not need to coordinate with each other. The driver only uses the primary
 * mailbox.
 */
static int __cxl_pci_mbox_send_cmd(struct cxl_dev_state *cxlds,
				   struct cxl_mbox_cmd *mbox_cmd)
{
	void __iomem *payload = cxlds->regs.mbox + CXLDEV_MBOX_PAYLOAD_OFFSET;
	struct device *dev = cxlds->dev;
	u64 cmd_reg, status_reg;
	size_t out_len;
	int rc;

	lockdep_assert_held(&cxlds->mbox_mutex);

	/*
	 * Here are the steps from 8.2.8.4 of the CXL 2.0 spec.
	 *   1. Caller reads MB Control Register to verify doorbell is clear
	 *   2. Caller writes Command Register
	 *   3. Caller writes Command Payload Registers if input payload is non-empty
	 *   4. Caller writes MB Control Register to set doorbell
	 *   5. Caller either polls for doorbell to be clear or waits for interrupt if configured
	 *   6. Caller reads MB Status Register to fetch Return code
	 *   7. If command successful, Caller reads Command Register to get Payload Length
	 *   8. If output payload is non-empty, host reads Command Payload Registers
	 *
	 * Hardware is free to do whatever it wants before the doorbell is rung,
	 * and isn't allowed to change anything after it clears the doorbell. As
	 * such, steps 2 and 3 can happen in any order, and steps 6, 7, 8 can
	 * also happen in any order (though some orders might not make sense).
	 */

	/* #1 */
	if (cxl_doorbell_busy(cxlds)) {
		u64 md_status =
			readq(cxlds->regs.memdev + CXLMDEV_STATUS_OFFSET);

		cxl_cmd_err(cxlds->dev, mbox_cmd, md_status,
			    "mailbox queue busy");
		return -EBUSY;
	}

	cmd_reg = FIELD_PREP(CXLDEV_MBOX_CMD_COMMAND_OPCODE_MASK,
			     mbox_cmd->opcode);
	if (mbox_cmd->size_in) {
		if (WARN_ON(!mbox_cmd->payload_in))
			return -EINVAL;

		cmd_reg |= FIELD_PREP(CXLDEV_MBOX_CMD_PAYLOAD_LENGTH_MASK,
				      mbox_cmd->size_in);
		memcpy_toio(payload, mbox_cmd->payload_in, mbox_cmd->size_in);
	}

	/* #2, #3 */
	writeq(cmd_reg, cxlds->regs.mbox + CXLDEV_MBOX_CMD_OFFSET);

	/* #4 */
	dev_dbg(dev, "Sending command\n");
	writel(CXLDEV_MBOX_CTRL_DOORBELL,
	       cxlds->regs.mbox + CXLDEV_MBOX_CTRL_OFFSET);

	/* #5 */
	rc = cxl_pci_mbox_wait_for_doorbell(cxlds);
	if (rc == -ETIMEDOUT) {
		u64 md_status = readq(cxlds->regs.memdev + CXLMDEV_STATUS_OFFSET);

		cxl_cmd_err(cxlds->dev, mbox_cmd, md_status, "mailbox timeout");
		return rc;
	}

	/* #6 */
	status_reg = readq(cxlds->regs.mbox + CXLDEV_MBOX_STATUS_OFFSET);
	mbox_cmd->return_code =
		FIELD_GET(CXLDEV_MBOX_STATUS_RET_CODE_MASK, status_reg);

	if (mbox_cmd->return_code != CXL_MBOX_CMD_RC_SUCCESS) {
		dev_dbg(dev, "Mailbox operation had an error: %s\n",
			cxl_mbox_cmd_rc2str(mbox_cmd));
		return 0; /* completed but caller must check return_code */
	}

	/* #7 */
	cmd_reg = readq(cxlds->regs.mbox + CXLDEV_MBOX_CMD_OFFSET);
	out_len = FIELD_GET(CXLDEV_MBOX_CMD_PAYLOAD_LENGTH_MASK, cmd_reg);

	/* #8 */
	if (out_len && mbox_cmd->payload_out) {
		/*
		 * Sanitize the copy. If hardware misbehaves, out_len per the
		 * spec can actually be greater than the max allowed size (21
		 * bits available but spec defined 1M max). The caller also may
		 * have requested less data than the hardware supplied even
		 * within spec.
		 */
		size_t n = min3(mbox_cmd->size_out, cxlds->payload_size, out_len);

		memcpy_fromio(mbox_cmd->payload_out, payload, n);
		mbox_cmd->size_out = n;
	} else {
		mbox_cmd->size_out = 0;
	}

	return 0;
}

static int cxl_pci_mbox_send(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd)
{
	int rc;

	mutex_lock_io(&cxlds->mbox_mutex);
	rc = __cxl_pci_mbox_send_cmd(cxlds, cmd);
	mutex_unlock(&cxlds->mbox_mutex);

	return rc;
}

static int cxl_pci_setup_mailbox(struct cxl_dev_state *cxlds)
{
	const int cap = readl(cxlds->regs.mbox + CXLDEV_MBOX_CAPS_OFFSET);
	unsigned long timeout;
	u64 md_status;

	timeout = jiffies + mbox_ready_timeout * HZ;
	do {
		md_status = readq(cxlds->regs.memdev + CXLMDEV_STATUS_OFFSET);
		if (md_status & CXLMDEV_MBOX_IF_READY)
			break;
		if (msleep_interruptible(100))
			break;
	} while (!time_after(jiffies, timeout));

	if (!(md_status & CXLMDEV_MBOX_IF_READY)) {
		cxl_err(cxlds->dev, md_status,
			"timeout awaiting mailbox ready");
		return -ETIMEDOUT;
	}

	/*
	 * A command may be in flight from a previous driver instance,
	 * think kexec, do one doorbell wait so that
	 * __cxl_pci_mbox_send_cmd() can assume that it is the only
	 * source for future doorbell busy events.
	 */
	if (cxl_pci_mbox_wait_for_doorbell(cxlds) != 0) {
		cxl_err(cxlds->dev, md_status, "timeout awaiting mailbox idle");
		return -ETIMEDOUT;
	}

	cxlds->mbox_send = cxl_pci_mbox_send;
	cxlds->payload_size =
		1 << FIELD_GET(CXLDEV_MBOX_CAP_PAYLOAD_SIZE_MASK, cap);

	/*
	 * CXL 2.0 8.2.8.4.3 Mailbox Capabilities Register
	 *
	 * If the size is too small, mandatory commands will not work and so
	 * there's no point in going forward. If the size is too large, there's
	 * no harm is soft limiting it.
	 */
	cxlds->payload_size = min_t(size_t, cxlds->payload_size, SZ_1M);
	if (cxlds->payload_size < 256) {
		dev_err(cxlds->dev, "Mailbox is too small (%zub)",
			cxlds->payload_size);
		return -ENXIO;
	}

	dev_dbg(cxlds->dev, "Mailbox payload sized %zu",
		cxlds->payload_size);

	return 0;
}

static int cxl_map_regblock(struct pci_dev *pdev, struct cxl_register_map *map)
{
	struct device *dev = &pdev->dev;

	map->base = ioremap(map->resource, map->max_size);
	if (!map->base) {
		dev_err(dev, "failed to map registers\n");
		return -ENOMEM;
	}

	dev_dbg(dev, "Mapped CXL Memory Device resource %pa\n", &map->resource);
	return 0;
}

static void cxl_unmap_regblock(struct pci_dev *pdev,
			       struct cxl_register_map *map)
{
	iounmap(map->base);
	map->base = NULL;
}

static int cxl_probe_regs(struct pci_dev *pdev, struct cxl_register_map *map)
{
	struct cxl_component_reg_map *comp_map;
	struct cxl_device_reg_map *dev_map;
	struct device *dev = &pdev->dev;
	void __iomem *base = map->base;

	switch (map->reg_type) {
	case CXL_REGLOC_RBI_COMPONENT:
		comp_map = &map->component_map;
		cxl_probe_component_regs(dev, base, comp_map);
		if (!comp_map->hdm_decoder.valid) {
			dev_err(dev, "HDM decoder registers not found\n");
			return -ENXIO;
		}

		if (!comp_map->ras.valid)
			dev_dbg(dev, "RAS registers not found\n");

		dev_dbg(dev, "Set up component registers\n");
		break;
	case CXL_REGLOC_RBI_MEMDEV:
		dev_map = &map->device_map;
		cxl_probe_device_regs(dev, base, dev_map);
		if (!dev_map->status.valid || !dev_map->mbox.valid ||
		    !dev_map->memdev.valid) {
			dev_err(dev, "registers not found: %s%s%s\n",
				!dev_map->status.valid ? "status " : "",
				!dev_map->mbox.valid ? "mbox " : "",
				!dev_map->memdev.valid ? "memdev " : "");
			return -ENXIO;
		}

		dev_dbg(dev, "Probing device registers...\n");
		break;
	default:
		break;
	}

	return 0;
}

static int cxl_setup_regs(struct pci_dev *pdev, enum cxl_regloc_type type,
			  struct cxl_register_map *map)
{
	int rc;

	rc = cxl_find_regblock(pdev, type, map);
	if (rc)
		return rc;

	rc = cxl_map_regblock(pdev, map);
	if (rc)
		return rc;

	rc = cxl_probe_regs(pdev, map);
	cxl_unmap_regblock(pdev, map);

	return rc;
}

static void cxl_pci_destroy_doe(void *mbs)
{
	xa_destroy(mbs);
}

static void devm_cxl_pci_create_doe(struct cxl_dev_state *cxlds)
{
	struct device *dev = cxlds->dev;
	struct pci_dev *pdev = to_pci_dev(dev);
	u16 off = 0;

	xa_init(&cxlds->doe_mbs);
	if (devm_add_action(&pdev->dev, cxl_pci_destroy_doe, &cxlds->doe_mbs)) {
		dev_err(dev, "Failed to create XArray for DOE's\n");
		return;
	}

	/*
	 * Mailbox creation is best effort.  Higher layers must determine if
	 * the lack of a mailbox for their protocol is a device failure or not.
	 */
	pci_doe_for_each_off(pdev, off) {
		struct pci_doe_mb *doe_mb;

		doe_mb = pcim_doe_create_mb(pdev, off);
		if (IS_ERR(doe_mb)) {
			dev_err(dev, "Failed to create MB object for MB @ %x\n",
				off);
			continue;
		}

		if (!pci_request_config_region_exclusive(pdev, off,
							 PCI_DOE_CAP_SIZEOF,
							 dev_name(dev)))
			pci_err(pdev, "Failed to exclude DOE registers\n");

		if (xa_insert(&cxlds->doe_mbs, off, doe_mb, GFP_KERNEL)) {
			dev_err(dev, "xa_insert failed to insert MB @ %x\n",
				off);
			continue;
		}

		dev_dbg(dev, "Created DOE mailbox @%x\n", off);
	}
}

/*
 * Assume that any RCIEP that emits the CXL memory expander class code
 * is an RCD
 */
static bool is_cxl_restricted(struct pci_dev *pdev)
{
	return pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END;
}

static void disable_aer(void *pdev)
{
	pci_disable_pcie_error_reporting(pdev);
}

static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
{
	struct cxl_register_map map;
	struct cxl_memdev *cxlmd;
	struct cxl_dev_state *cxlds;
	int rc;

	/*
	 * Double check the anonymous union trickery in struct cxl_regs
	 * FIXME switch to struct_group()
	 */
	BUILD_BUG_ON(offsetof(struct cxl_regs, memdev) !=
		     offsetof(struct cxl_regs, device_regs.memdev));

	rc = pcim_enable_device(pdev);
	if (rc)
		return rc;

	cxlds = cxl_dev_state_create(&pdev->dev);
	if (IS_ERR(cxlds))
		return PTR_ERR(cxlds);
	pci_set_drvdata(pdev, cxlds);

	cxlds->rcd = is_cxl_restricted(pdev);
	cxlds->serial = pci_get_dsn(pdev);
	cxlds->cxl_dvsec = pci_find_dvsec_capability(
		pdev, PCI_DVSEC_VENDOR_ID_CXL, CXL_DVSEC_PCIE_DEVICE);
	if (!cxlds->cxl_dvsec)
		dev_warn(&pdev->dev,
			 "Device DVSEC not present, skip CXL.mem init\n");

	rc = cxl_setup_regs(pdev, CXL_REGLOC_RBI_MEMDEV, &map);
	if (rc)
		return rc;

	rc = cxl_map_device_regs(&pdev->dev, &cxlds->regs.device_regs, &map);
	if (rc)
		return rc;

	/*
	 * If the component registers can't be found, the cxl_pci driver may
	 * still be useful for management functions so don't return an error.
	 */
	cxlds->component_reg_phys = CXL_RESOURCE_NONE;
	rc = cxl_setup_regs(pdev, CXL_REGLOC_RBI_COMPONENT, &map);
	if (rc)
		dev_warn(&pdev->dev, "No component registers (%d)\n", rc);

	cxlds->component_reg_phys = map.resource;

	devm_cxl_pci_create_doe(cxlds);

	rc = cxl_map_component_regs(&pdev->dev, &cxlds->regs.component,
				    &map, BIT(CXL_CM_CAP_CAP_ID_RAS));
	if (rc)
		dev_dbg(&pdev->dev, "Failed to map RAS capability.\n");

	rc = cxl_pci_setup_mailbox(cxlds);
	if (rc)
		return rc;

	rc = cxl_enumerate_cmds(cxlds);
	if (rc)
		return rc;

	rc = cxl_dev_state_identify(cxlds);
	if (rc)
		return rc;

	rc = cxl_mem_create_range_info(cxlds);
	if (rc)
		return rc;

	cxlmd = devm_cxl_add_memdev(cxlds);
	if (IS_ERR(cxlmd))
		return PTR_ERR(cxlmd);

	if (cxlds->regs.ras) {
		pci_enable_pcie_error_reporting(pdev);
		rc = devm_add_action_or_reset(&pdev->dev, disable_aer, pdev);
		if (rc)
			return rc;
	}
	pci_save_state(pdev);

	return rc;
}

static const struct pci_device_id cxl_mem_pci_tbl[] = {
	/* PCI class code for CXL.mem Type-3 Devices */
	{ PCI_DEVICE_CLASS((PCI_CLASS_MEMORY_CXL << 8 | CXL_MEMORY_PROGIF), ~0)},
	{ /* terminate list */ },
};
MODULE_DEVICE_TABLE(pci, cxl_mem_pci_tbl);

/* CXL spec rev3.0 8.2.4.16.1 */
static void header_log_copy(struct cxl_dev_state *cxlds, u32 *log)
{
	void __iomem *addr;
	u32 *log_addr;
	int i, log_u32_size = CXL_HEADERLOG_SIZE / sizeof(u32);

	addr = cxlds->regs.ras + CXL_RAS_HEADER_LOG_OFFSET;
	log_addr = log;

	for (i = 0; i < log_u32_size; i++) {
		*log_addr = readl(addr);
		log_addr++;
		addr += sizeof(u32);
	}
}

/*
 * Log the state of the RAS status registers and prepare them to log the
 * next error status. Return 1 if reset needed.
 */
static bool cxl_report_and_clear(struct cxl_dev_state *cxlds)
{
	struct cxl_memdev *cxlmd = cxlds->cxlmd;
	struct device *dev = &cxlmd->dev;
	u32 hl[CXL_HEADERLOG_SIZE_U32];
	void __iomem *addr;
	u32 status;
	u32 fe;

	if (!cxlds->regs.ras)
		return false;

	addr = cxlds->regs.ras + CXL_RAS_UNCORRECTABLE_STATUS_OFFSET;
	status = readl(addr);
	if (!(status & CXL_RAS_UNCORRECTABLE_STATUS_MASK))
		return false;

	/* If multiple errors, log header points to first error from ctrl reg */
	if (hweight32(status) > 1) {
		addr = cxlds->regs.ras + CXL_RAS_CAP_CONTROL_OFFSET;
		fe = BIT(FIELD_GET(CXL_RAS_CAP_CONTROL_FE_MASK, readl(addr)));
	} else {
		fe = status;
	}

	header_log_copy(cxlds, hl);
	trace_cxl_aer_uncorrectable_error(dev, status, fe, hl);
	writel(status & CXL_RAS_UNCORRECTABLE_STATUS_MASK, addr);

	return true;
}

static pci_ers_result_t cxl_error_detected(struct pci_dev *pdev,
					   pci_channel_state_t state)
{
	struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
	struct cxl_memdev *cxlmd = cxlds->cxlmd;
	struct device *dev = &cxlmd->dev;
	bool ue;

	/*
	 * A frozen channel indicates an impending reset which is fatal to
	 * CXL.mem operation, and will likely crash the system. On the off
	 * chance the situation is recoverable dump the status of the RAS
	 * capability registers and bounce the active state of the memdev.
	 */
	ue = cxl_report_and_clear(cxlds);

	switch (state) {
	case pci_channel_io_normal:
		if (ue) {
			device_release_driver(dev);
			return PCI_ERS_RESULT_NEED_RESET;
		}
		return PCI_ERS_RESULT_CAN_RECOVER;
	case pci_channel_io_frozen:
		dev_warn(&pdev->dev,
			 "%s: frozen state error detected, disable CXL.mem\n",
			 dev_name(dev));
		device_release_driver(dev);
		return PCI_ERS_RESULT_NEED_RESET;
	case pci_channel_io_perm_failure:
		dev_warn(&pdev->dev,
			 "failure state error detected, request disconnect\n");
		return PCI_ERS_RESULT_DISCONNECT;
	}
	return PCI_ERS_RESULT_NEED_RESET;
}

static pci_ers_result_t cxl_slot_reset(struct pci_dev *pdev)
{
	struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
	struct cxl_memdev *cxlmd = cxlds->cxlmd;
	struct device *dev = &cxlmd->dev;

	dev_info(&pdev->dev, "%s: restart CXL.mem after slot reset\n",
		 dev_name(dev));
	pci_restore_state(pdev);
	if (device_attach(dev) <= 0)
		return PCI_ERS_RESULT_DISCONNECT;
	return PCI_ERS_RESULT_RECOVERED;
}

static void cxl_error_resume(struct pci_dev *pdev)
{
	struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
	struct cxl_memdev *cxlmd = cxlds->cxlmd;
	struct device *dev = &cxlmd->dev;

	dev_info(&pdev->dev, "%s: error resume %s\n", dev_name(dev),
		 dev->driver ? "successful" : "failed");
}

static void cxl_cor_error_detected(struct pci_dev *pdev)
{
	struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
	struct cxl_memdev *cxlmd = cxlds->cxlmd;
	struct device *dev = &cxlmd->dev;
	void __iomem *addr;
	u32 status;

	if (!cxlds->regs.ras)
		return;

	addr = cxlds->regs.ras + CXL_RAS_CORRECTABLE_STATUS_OFFSET;
	status = readl(addr);
	if (status & CXL_RAS_CORRECTABLE_STATUS_MASK) {
		writel(status & CXL_RAS_CORRECTABLE_STATUS_MASK, addr);
		trace_cxl_aer_correctable_error(dev, status);
	}
}

static const struct pci_error_handlers cxl_error_handlers = {
	.error_detected	= cxl_error_detected,
	.slot_reset	= cxl_slot_reset,
	.resume		= cxl_error_resume,
	.cor_error_detected	= cxl_cor_error_detected,
};

static struct pci_driver cxl_pci_driver = {
	.name			= KBUILD_MODNAME,
	.id_table		= cxl_mem_pci_tbl,
	.probe			= cxl_pci_probe,
	.err_handler		= &cxl_error_handlers,
	.driver	= {
		.probe_type	= PROBE_PREFER_ASYNCHRONOUS,
	},
};

MODULE_LICENSE("GPL v2");
module_pci_driver(cxl_pci_driver);
MODULE_IMPORT_NS(CXL);