virtio_pci.c

Go to the documentation of this file.

/*
 * Virtio PCI driver
 *
 * This module allows virtio devices to be used over a virtual PCI device.
 * This can be used with QEMU based VMMs like KVM or Xen.
 *
 * Copyright IBM Corp. 2007
 *
 * Authors:
 *  Anthony Liguori  <[email protected]>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 *
 */

#include <linux/module.h>
#include <linux/list.h>
#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/virtio.h>
#include <linux/virtio_config.h>
#include <linux/virtio_ring.h>
#include <linux/virtio_pci.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>

MODULE_AUTHOR("Anthony Liguori <[email protected]>");
MODULE_DESCRIPTION("virtio-pci");
MODULE_LICENSE("GPL");
MODULE_VERSION("1");

/* Our device structure */
struct virtio_pci_device
{
    struct virtio_device vdev;
    struct pci_dev *pci_dev;

    /* the IO mapping for the PCI config space */
    void __iomem *ioaddr;

    /* a list of queues so we can dispatch IRQs */
    spinlock_t lock;
    struct list_head virtqueues;

    /* MSI-X support */
    int msix_enabled;
    int intx_enabled;
    struct msix_entry *msix_entries;
    cpumask_var_t *msix_affinity_masks;
    /* Name strings for interrupts. This size should be enough,
     * and I'm too lazy to allocate each name separately. */
    char (*msix_names)[256];
    /* Number of available vectors */
    unsigned msix_vectors;
    /* Vectors allocated, excluding per-vq vectors if any */
    unsigned msix_used_vectors;

    /* Status saved during hibernate/restore */
    u8 saved_status;

    /* Whether we have vector per vq */
    bool per_vq_vectors;
};

/* Constants for MSI-X */
/* Use first vector for configuration changes, second and the rest for
 * virtqueues Thus, we need at least 2 vectors for MSI. */
enum {
    VP_MSIX_CONFIG_VECTOR = 0,
    VP_MSIX_VQ_VECTOR = 1,
};

struct virtio_pci_vq_info
{
    /* the actual virtqueue */
    struct virtqueue *vq;

    /* the number of entries in the queue */
    int num;

    /* the virtual address of the ring queue */
    void *queue;

    /* the list node for the virtqueues list */
    struct list_head node;

    /* MSI-X vector (or none) */
    unsigned msix_vector;
};

/* Qumranet donated their vendor ID for devices 0x1000 thru 0x10FF. */
static struct pci_device_id virtio_pci_id_table[] = {
    { 0x1af4, PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 },
    { 0 },
};

MODULE_DEVICE_TABLE(pci, virtio_pci_id_table);

/* Convert a generic virtio device to our structure */
static struct virtio_pci_device *to_vp_device(struct virtio_device *vdev)
{
    return container_of(vdev, struct virtio_pci_device, vdev);
}

/* virtio config->get_features() implementation */
static u32 vp_get_features(struct virtio_device *vdev)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);

    /* When someone needs more than 32 feature bits, we'll need to
     * steal a bit to indicate that the rest are somewhere else. */
    return ioread32(vp_dev->ioaddr + VIRTIO_PCI_HOST_FEATURES);
}

/* virtio config->finalize_features() implementation */
static void vp_finalize_features(struct virtio_device *vdev)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);

    /* Give virtio_ring a chance to accept features. */
    vring_transport_features(vdev);

    /* We only support 32 feature bits. */
    BUILD_BUG_ON(ARRAY_SIZE(vdev->features) != 1);
    iowrite32(vdev->features[0], vp_dev->ioaddr+VIRTIO_PCI_GUEST_FEATURES);
}

/* virtio config->get() implementation */
static void vp_get(struct virtio_device *vdev, unsigned offset,
           void *buf, unsigned len)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    void __iomem *ioaddr = vp_dev->ioaddr +
                VIRTIO_PCI_CONFIG(vp_dev) + offset;
    u8 *ptr = buf;
    int i;

    for (i = 0; i < len; i++)
        ptr[i] = ioread8(ioaddr + i);
}

/* the config->set() implementation.  it's symmetric to the config->get()
 * implementation */
static void vp_set(struct virtio_device *vdev, unsigned offset,
           const void *buf, unsigned len)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    void __iomem *ioaddr = vp_dev->ioaddr +
                VIRTIO_PCI_CONFIG(vp_dev) + offset;
    const u8 *ptr = buf;
    int i;

    for (i = 0; i < len; i++)
        iowrite8(ptr[i], ioaddr + i);
}

/* config->{get,set}_status() implementations */
static u8 vp_get_status(struct virtio_device *vdev)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    return ioread8(vp_dev->ioaddr + VIRTIO_PCI_STATUS);
}

static void vp_set_status(struct virtio_device *vdev, u8 status)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    /* We should never be setting status to 0. */
    BUG_ON(status == 0);
    iowrite8(status, vp_dev->ioaddr + VIRTIO_PCI_STATUS);
}

/* wait for pending irq handlers */
static void vp_synchronize_vectors(struct virtio_device *vdev)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    int i;

    if (vp_dev->intx_enabled)
        synchronize_irq(vp_dev->pci_dev->irq);

    for (i = 0; i < vp_dev->msix_vectors; ++i)
        synchronize_irq(vp_dev->msix_entries[i].vector);
}

static void vp_reset(struct virtio_device *vdev)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    /* 0 status means a reset. */
    iowrite8(0, vp_dev->ioaddr + VIRTIO_PCI_STATUS);
    /* Flush out the status write, and flush in device writes,
     * including MSi-X interrupts, if any. */
    ioread8(vp_dev->ioaddr + VIRTIO_PCI_STATUS);
    /* Flush pending VQ/configuration callbacks. */
    vp_synchronize_vectors(vdev);
}

/* the notify function used when creating a virt queue */
static void vp_notify(struct virtqueue *vq)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);

    /* we write the queue's selector into the notification register to
     * signal the other end */
    iowrite16(virtqueue_get_queue_index(vq),
          vp_dev->ioaddr + VIRTIO_PCI_QUEUE_NOTIFY);
}

/* Handle a configuration change: Tell driver if it wants to know. */
static irqreturn_t vp_config_changed(int irq, void *opaque)
{
    struct virtio_pci_device *vp_dev = opaque;
    struct virtio_driver *drv;
    drv = container_of(vp_dev->vdev.dev.driver,
               struct virtio_driver, driver);

    if (drv && drv->config_changed)
        drv->config_changed(&vp_dev->vdev);
    return IRQ_HANDLED;
}

/* Notify all virtqueues on an interrupt. */
static irqreturn_t vp_vring_interrupt(int irq, void *opaque)
{
    struct virtio_pci_device *vp_dev = opaque;
    struct virtio_pci_vq_info *info;
    irqreturn_t ret = IRQ_NONE;
    unsigned long flags;

    spin_lock_irqsave(&vp_dev->lock, flags);
    list_for_each_entry(info, &vp_dev->virtqueues, node) {
        if (vring_interrupt(irq, info->vq) == IRQ_HANDLED)
            ret = IRQ_HANDLED;
    }
    spin_unlock_irqrestore(&vp_dev->lock, flags);

    return ret;
}

/* A small wrapper to also acknowledge the interrupt when it's handled.
 * I really need an EIO hook for the vring so I can ack the interrupt once we
 * know that we'll be handling the IRQ but before we invoke the callback since
 * the callback may notify the host which results in the host attempting to
 * raise an interrupt that we would then mask once we acknowledged the
 * interrupt. */
static irqreturn_t vp_interrupt(int irq, void *opaque)
{
    struct virtio_pci_device *vp_dev = opaque;
    u8 isr;

    /* reading the ISR has the effect of also clearing it so it's very
     * important to save off the value. */
    isr = ioread8(vp_dev->ioaddr + VIRTIO_PCI_ISR);

    /* It's definitely not us if the ISR was not high */
    if (!isr)
        return IRQ_NONE;

    /* Configuration change?  Tell driver if it wants to know. */
    if (isr & VIRTIO_PCI_ISR_CONFIG)
        vp_config_changed(irq, opaque);

    return vp_vring_interrupt(irq, opaque);
}

static void vp_free_vectors(struct virtio_device *vdev)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    int i;

    if (vp_dev->intx_enabled) {
        free_irq(vp_dev->pci_dev->irq, vp_dev);
        vp_dev->intx_enabled = 0;
    }

    for (i = 0; i < vp_dev->msix_used_vectors; ++i)
        free_irq(vp_dev->msix_entries[i].vector, vp_dev);

    for (i = 0; i < vp_dev->msix_vectors; i++)
        if (vp_dev->msix_affinity_masks[i])
            free_cpumask_var(vp_dev->msix_affinity_masks[i]);

    if (vp_dev->msix_enabled) {
        /* Disable the vector used for configuration */
        iowrite16(VIRTIO_MSI_NO_VECTOR,
              vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
        /* Flush the write out to device */
        ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);

        pci_disable_msix(vp_dev->pci_dev);
        vp_dev->msix_enabled = 0;
        vp_dev->msix_vectors = 0;
    }

    vp_dev->msix_used_vectors = 0;
    kfree(vp_dev->msix_names);
    vp_dev->msix_names = NULL;
    kfree(vp_dev->msix_entries);
    vp_dev->msix_entries = NULL;
    kfree(vp_dev->msix_affinity_masks);
    vp_dev->msix_affinity_masks = NULL;
}

static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
                   bool per_vq_vectors)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    const char *name = dev_name(&vp_dev->vdev.dev);
    unsigned i, v;
    int err = -ENOMEM;

    vp_dev->msix_entries = kmalloc(nvectors * sizeof *vp_dev->msix_entries,
                       GFP_KERNEL);
    if (!vp_dev->msix_entries)
        goto error;
    vp_dev->msix_names = kmalloc(nvectors * sizeof *vp_dev->msix_names,
                     GFP_KERNEL);
    if (!vp_dev->msix_names)
        goto error;
    vp_dev->msix_affinity_masks
        = kzalloc(nvectors * sizeof *vp_dev->msix_affinity_masks,
              GFP_KERNEL);
    if (!vp_dev->msix_affinity_masks)
        goto error;
    for (i = 0; i < nvectors; ++i)
        if (!alloc_cpumask_var(&vp_dev->msix_affinity_masks[i],
                    GFP_KERNEL))
            goto error;

    for (i = 0; i < nvectors; ++i)
        vp_dev->msix_entries[i].entry = i;

    /* pci_enable_msix returns positive if we can't get this many. */
    err = pci_enable_msix(vp_dev->pci_dev, vp_dev->msix_entries, nvectors);
    if (err > 0)
        err = -ENOSPC;
    if (err)
        goto error;
    vp_dev->msix_vectors = nvectors;
    vp_dev->msix_enabled = 1;

    /* Set the vector used for configuration */
    v = vp_dev->msix_used_vectors;
    snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
         "%s-config", name);
    err = request_irq(vp_dev->msix_entries[v].vector,
              vp_config_changed, 0, vp_dev->msix_names[v],
              vp_dev);
    if (err)
        goto error;
    ++vp_dev->msix_used_vectors;

    iowrite16(v, vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
    /* Verify we had enough resources to assign the vector */
    v = ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
    if (v == VIRTIO_MSI_NO_VECTOR) {
        err = -EBUSY;
        goto error;
    }

    if (!per_vq_vectors) {
        /* Shared vector for all VQs */
        v = vp_dev->msix_used_vectors;
        snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
             "%s-virtqueues", name);
        err = request_irq(vp_dev->msix_entries[v].vector,
                  vp_vring_interrupt, 0, vp_dev->msix_names[v],
                  vp_dev);
        if (err)
            goto error;
        ++vp_dev->msix_used_vectors;
    }
    return 0;
error:
    vp_free_vectors(vdev);
    return err;
}

static int vp_request_intx(struct virtio_device *vdev)
{
    int err;
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);

    err = request_irq(vp_dev->pci_dev->irq, vp_interrupt,
              IRQF_SHARED, dev_name(&vdev->dev), vp_dev);
    if (!err)
        vp_dev->intx_enabled = 1;
    return err;
}

static struct virtqueue *setup_vq(struct virtio_device *vdev, unsigned index,
                  void (*callback)(struct virtqueue *vq),
                  const char *name,
                  u16 msix_vec)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    struct virtio_pci_vq_info *info;
    struct virtqueue *vq;
    unsigned long flags, size;
    u16 num;
    int err;

    /* Select the queue we're interested in */
    iowrite16(index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);

    /* Check if queue is either not available or already active. */
    num = ioread16(vp_dev->ioaddr + VIRTIO_PCI_QUEUE_NUM);
    if (!num || ioread32(vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN))
        return ERR_PTR(-ENOENT);

    /* allocate and fill out our structure the represents an active
     * queue */
    info = kmalloc(sizeof(struct virtio_pci_vq_info), GFP_KERNEL);
    if (!info)
        return ERR_PTR(-ENOMEM);

    info->num = num;
    info->msix_vector = msix_vec;

    size = PAGE_ALIGN(vring_size(num, VIRTIO_PCI_VRING_ALIGN));
    info->queue = alloc_pages_exact(size, GFP_KERNEL|__GFP_ZERO);
    if (info->queue == NULL) {
        err = -ENOMEM;
        goto out_info;
    }

    /* activate the queue */
    iowrite32(virt_to_phys(info->queue) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT,
          vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);

    /* create the vring */
    vq = vring_new_virtqueue(index, info->num, VIRTIO_PCI_VRING_ALIGN, vdev,
                 true, info->queue, vp_notify, callback, name);
    if (!vq) {
        err = -ENOMEM;
        goto out_activate_queue;
    }

    vq->priv = info;
    info->vq = vq;

    if (msix_vec != VIRTIO_MSI_NO_VECTOR) {
        iowrite16(msix_vec, vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
        msix_vec = ioread16(vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
        if (msix_vec == VIRTIO_MSI_NO_VECTOR) {
            err = -EBUSY;
            goto out_assign;
        }
    }

    if (callback) {
        spin_lock_irqsave(&vp_dev->lock, flags);
        list_add(&info->node, &vp_dev->virtqueues);
        spin_unlock_irqrestore(&vp_dev->lock, flags);
    } else {
        INIT_LIST_HEAD(&info->node);
    }

    return vq;

out_assign:
    vring_del_virtqueue(vq);
out_activate_queue:
    iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
    free_pages_exact(info->queue, size);
out_info:
    kfree(info);
    return ERR_PTR(err);
}

static void vp_del_vq(struct virtqueue *vq)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
    struct virtio_pci_vq_info *info = vq->priv;
    unsigned long flags, size;

    spin_lock_irqsave(&vp_dev->lock, flags);
    list_del(&info->node);
    spin_unlock_irqrestore(&vp_dev->lock, flags);

    iowrite16(virtqueue_get_queue_index(vq),
        vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);

    if (vp_dev->msix_enabled) {
        iowrite16(VIRTIO_MSI_NO_VECTOR,
              vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
        /* Flush the write out to device */
        ioread8(vp_dev->ioaddr + VIRTIO_PCI_ISR);
    }

    vring_del_virtqueue(vq);

    /* Select and deactivate the queue */
    iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);

    size = PAGE_ALIGN(vring_size(info->num, VIRTIO_PCI_VRING_ALIGN));
    free_pages_exact(info->queue, size);
    kfree(info);
}

/* the config->del_vqs() implementation */
static void vp_del_vqs(struct virtio_device *vdev)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    struct virtqueue *vq, *n;
    struct virtio_pci_vq_info *info;

    list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
        info = vq->priv;
        if (vp_dev->per_vq_vectors &&
            info->msix_vector != VIRTIO_MSI_NO_VECTOR)
            free_irq(vp_dev->msix_entries[info->msix_vector].vector,
                 vq);
        vp_del_vq(vq);
    }
    vp_dev->per_vq_vectors = false;

    vp_free_vectors(vdev);
}

static int vp_try_to_find_vqs(struct virtio_device *vdev, unsigned nvqs,
                  struct virtqueue *vqs[],
                  vq_callback_t *callbacks[],
                  const char *names[],
                  bool use_msix,
                  bool per_vq_vectors)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    u16 msix_vec;
    int i, err, nvectors, allocated_vectors;

    if (!use_msix) {
        /* Old style: one normal interrupt for change and all vqs. */
        err = vp_request_intx(vdev);
        if (err)
            goto error_request;
    } else {
        if (per_vq_vectors) {
            /* Best option: one for change interrupt, one per vq. */
            nvectors = 1;
            for (i = 0; i < nvqs; ++i)
                if (callbacks[i])
                    ++nvectors;
        } else {
            /* Second best: one for change, shared for all vqs. */
            nvectors = 2;
        }

        err = vp_request_msix_vectors(vdev, nvectors, per_vq_vectors);
        if (err)
            goto error_request;
    }

    vp_dev->per_vq_vectors = per_vq_vectors;
    allocated_vectors = vp_dev->msix_used_vectors;
    for (i = 0; i < nvqs; ++i) {
        if (!names[i]) {
            vqs[i] = NULL;
            continue;
        } else if (!callbacks[i] || !vp_dev->msix_enabled)
            msix_vec = VIRTIO_MSI_NO_VECTOR;
        else if (vp_dev->per_vq_vectors)
            msix_vec = allocated_vectors++;
        else
            msix_vec = VP_MSIX_VQ_VECTOR;
        vqs[i] = setup_vq(vdev, i, callbacks[i], names[i], msix_vec);
        if (IS_ERR(vqs[i])) {
            err = PTR_ERR(vqs[i]);
            goto error_find;
        }

        if (!vp_dev->per_vq_vectors || msix_vec == VIRTIO_MSI_NO_VECTOR)
            continue;

        /* allocate per-vq irq if available and necessary */
        snprintf(vp_dev->msix_names[msix_vec],
             sizeof *vp_dev->msix_names,
             "%s-%s",
             dev_name(&vp_dev->vdev.dev), names[i]);
        err = request_irq(vp_dev->msix_entries[msix_vec].vector,
                  vring_interrupt, 0,
                  vp_dev->msix_names[msix_vec],
                  vqs[i]);
        if (err) {
            vp_del_vq(vqs[i]);
            goto error_find;
        }
    }
    return 0;

error_find:
    vp_del_vqs(vdev);

error_request:
    return err;
}

/* the config->find_vqs() implementation */
static int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
               struct virtqueue *vqs[],
               vq_callback_t *callbacks[],
               const char *names[])
{
    int err;

    /* Try MSI-X with one vector per queue. */
    err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names, true, true);
    if (!err)
        return 0;
    /* Fallback: MSI-X with one vector for config, one shared for queues. */
    err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
                 true, false);
    if (!err)
        return 0;
    /* Finally fall back to regular interrupts. */
    return vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
                  false, false);
}

static const char *vp_bus_name(struct virtio_device *vdev)
{
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);

    return pci_name(vp_dev->pci_dev);
}

/* Setup the affinity for a virtqueue:
 * - force the affinity for per vq vector
 * - OR over all affinities for shared MSI
 * - ignore the affinity request if we're using INTX
 */
static int vp_set_vq_affinity(struct virtqueue *vq, int cpu)
{
    struct virtio_device *vdev = vq->vdev;
    struct virtio_pci_device *vp_dev = to_vp_device(vdev);
    struct virtio_pci_vq_info *info = vq->priv;
    struct cpumask *mask;
    unsigned int irq;

    if (!vq->callback)
        return -EINVAL;

    if (vp_dev->msix_enabled) {
        mask = vp_dev->msix_affinity_masks[info->msix_vector];
        irq = vp_dev->msix_entries[info->msix_vector].vector;
        if (cpu == -1)
            irq_set_affinity_hint(irq, NULL);
        else {
            cpumask_set_cpu(cpu, mask);
            irq_set_affinity_hint(irq, mask);
        }
    }
    return 0;
}

static struct virtio_config_ops virtio_pci_config_ops = {
    .get        = vp_get,
    .set        = vp_set,
    .get_status = vp_get_status,
    .set_status = vp_set_status,
    .reset      = vp_reset,
    .find_vqs   = vp_find_vqs,
    .del_vqs    = vp_del_vqs,
    .get_features   = vp_get_features,
    .finalize_features = vp_finalize_features,
    .bus_name   = vp_bus_name,
    .set_vq_affinity = vp_set_vq_affinity,
};

static void virtio_pci_release_dev(struct device *_d)
{
    /*
     * No need for a release method as we allocate/free
     * all devices together with the pci devices.
     * Provide an empty one to avoid getting a warning from core.
     */
}

/* the PCI probing function */
static int __devinit virtio_pci_probe(struct pci_dev *pci_dev,
                      const struct pci_device_id *id)
{
    struct virtio_pci_device *vp_dev;
    int err;

    /* We only own devices >= 0x1000 and <= 0x103f: leave the rest. */
    if (pci_dev->device < 0x1000 || pci_dev->device > 0x103f)
        return -ENODEV;

    if (pci_dev->revision != VIRTIO_PCI_ABI_VERSION) {
        printk(KERN_ERR "virtio_pci: expected ABI version %d, got %d\n",
               VIRTIO_PCI_ABI_VERSION, pci_dev->revision);
        return -ENODEV;
    }

    /* allocate our structure and fill it out */
    vp_dev = kzalloc(sizeof(struct virtio_pci_device), GFP_KERNEL);
    if (vp_dev == NULL)
        return -ENOMEM;

    vp_dev->vdev.dev.parent = &pci_dev->dev;
    vp_dev->vdev.dev.release = virtio_pci_release_dev;
    vp_dev->vdev.config = &virtio_pci_config_ops;
    vp_dev->pci_dev = pci_dev;
    INIT_LIST_HEAD(&vp_dev->virtqueues);
    spin_lock_init(&vp_dev->lock);

    /* Disable MSI/MSIX to bring device to a known good state. */
    pci_msi_off(pci_dev);

    /* enable the device */
    err = pci_enable_device(pci_dev);
    if (err)
        goto out;

    err = pci_request_regions(pci_dev, "virtio-pci");
    if (err)
        goto out_enable_device;

    vp_dev->ioaddr = pci_iomap(pci_dev, 0, 0);
    if (vp_dev->ioaddr == NULL) {
        err = -ENOMEM;
        goto out_req_regions;
    }

    pci_set_drvdata(pci_dev, vp_dev);
    pci_set_master(pci_dev);

    /* we use the subsystem vendor/device id as the virtio vendor/device
     * id.  this allows us to use the same PCI vendor/device id for all
     * virtio devices and to identify the particular virtio driver by
     * the subsystem ids */
    vp_dev->vdev.id.vendor = pci_dev->subsystem_vendor;
    vp_dev->vdev.id.device = pci_dev->subsystem_device;

    /* finally register the virtio device */
    err = register_virtio_device(&vp_dev->vdev);
    if (err)
        goto out_set_drvdata;

    return 0;

out_set_drvdata:
    pci_set_drvdata(pci_dev, NULL);
    pci_iounmap(pci_dev, vp_dev->ioaddr);
out_req_regions:
    pci_release_regions(pci_dev);
out_enable_device:
    pci_disable_device(pci_dev);
out:
    kfree(vp_dev);
    return err;
}

static void __devexit virtio_pci_remove(struct pci_dev *pci_dev)
{
    struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);

    unregister_virtio_device(&vp_dev->vdev);

    vp_del_vqs(&vp_dev->vdev);
    pci_set_drvdata(pci_dev, NULL);
    pci_iounmap(pci_dev, vp_dev->ioaddr);
    pci_release_regions(pci_dev);
    pci_disable_device(pci_dev);
    kfree(vp_dev);
}

#ifdef CONFIG_PM
static int virtio_pci_freeze(struct device *dev)
{
    struct pci_dev *pci_dev = to_pci_dev(dev);
    struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
    struct virtio_driver *drv;
    int ret;

    drv = container_of(vp_dev->vdev.dev.driver,
               struct virtio_driver, driver);

    ret = 0;
    vp_dev->saved_status = vp_get_status(&vp_dev->vdev);
    if (drv && drv->freeze)
        ret = drv->freeze(&vp_dev->vdev);

    if (!ret)
        pci_disable_device(pci_dev);
    return ret;
}

static int virtio_pci_restore(struct device *dev)
{
    struct pci_dev *pci_dev = to_pci_dev(dev);
    struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
    struct virtio_driver *drv;
    int ret;

    drv = container_of(vp_dev->vdev.dev.driver,
               struct virtio_driver, driver);

    ret = pci_enable_device(pci_dev);
    if (ret)
        return ret;

    pci_set_master(pci_dev);
    vp_finalize_features(&vp_dev->vdev);

    if (drv && drv->restore)
        ret = drv->restore(&vp_dev->vdev);

    /* Finally, tell the device we're all set */
    if (!ret)
        vp_set_status(&vp_dev->vdev, vp_dev->saved_status);

    return ret;
}

static const struct dev_pm_ops virtio_pci_pm_ops = {
    SET_SYSTEM_SLEEP_PM_OPS(virtio_pci_freeze, virtio_pci_restore)
};
#endif

static struct pci_driver virtio_pci_driver = {
    .name       = "virtio-pci",
    .id_table   = virtio_pci_id_table,
    .probe      = virtio_pci_probe,
    .remove     = __devexit_p(virtio_pci_remove),
#ifdef CONFIG_PM
    .driver.pm  = &virtio_pci_pm_ops,
#endif
};

static int __init virtio_pci_init(void)
{
    return pci_register_driver(&virtio_pci_driver);
}

module_init(virtio_pci_init);

static void __exit virtio_pci_exit(void)
{
    pci_unregister_driver(&virtio_pci_driver);
}

module_exit(virtio_pci_exit);