Archipelago » qemu

/*

 * Virtio Support

 *

 * Copyright IBM, Corp. 2007

 *

 * Authors:

 *  Anthony Liguori   <aliguori@us.ibm.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2.  See

 * the COPYING file in the top-level directory.

 *

 */

#include <inttypes.h>

#include "trace.h"

#include "qemu-error.h"

#include "virtio.h"

#include "qemu-barrier.h"

/* The alignment to use between consumer and producer parts of vring.

 * x86 pagesize again. */

#define VIRTIO_PCI_VRING_ALIGN         4096

typedef struct VRingDesc

{

    uint64_t addr;

    uint32_t len;

    uint16_t flags;

    uint16_t next;

} VRingDesc;

typedef struct VRingAvail

{

    uint16_t flags;

    uint16_t idx;

    uint16_t ring[0];

} VRingAvail;

typedef struct VRingUsedElem

{

    uint32_t id;

    uint32_t len;

} VRingUsedElem;

typedef struct VRingUsed

{

    uint16_t flags;

    uint16_t idx;

    VRingUsedElem ring[0];

} VRingUsed;

typedef struct VRing

{

    unsigned int num;

    hwaddr desc;

    hwaddr avail;

    hwaddr used;

} VRing;

struct VirtQueue

{

    VRing vring;

    hwaddr pa;

    uint16_t last_avail_idx;

    /* Last used index value we have signalled on */

    uint16_t signalled_used;

    /* Last used index value we have signalled on */

    bool signalled_used_valid;

    /* Notification enabled? */

    bool notification;

    int inuse;

    uint16_t vector;

    void (*handle_output)(VirtIODevice *vdev, VirtQueue *vq);

    VirtIODevice *vdev;

    EventNotifier guest_notifier;

    EventNotifier host_notifier;

};

/* virt queue functions */

static void virtqueue_init(VirtQueue *vq)

{

    hwaddr pa = vq->pa;

    vq->vring.desc = pa;

    vq->vring.avail = pa + vq->vring.num * sizeof(VRingDesc);

    vq->vring.used = vring_align(vq->vring.avail +

                                 offsetof(VRingAvail, ring[vq->vring.num]),

                                 VIRTIO_PCI_VRING_ALIGN);

}

static inline uint64_t vring_desc_addr(hwaddr desc_pa, int i)

{

    hwaddr pa;

    pa = desc_pa + sizeof(VRingDesc) * i + offsetof(VRingDesc, addr);

    return ldq_phys(pa);

}

static inline uint32_t vring_desc_len(hwaddr desc_pa, int i)

{

    hwaddr pa;

    pa = desc_pa + sizeof(VRingDesc) * i + offsetof(VRingDesc, len);

    return ldl_phys(pa);

}

static inline uint16_t vring_desc_flags(hwaddr desc_pa, int i)

{

    hwaddr pa;

    pa = desc_pa + sizeof(VRingDesc) * i + offsetof(VRingDesc, flags);

    return lduw_phys(pa);

}

static inline uint16_t vring_desc_next(hwaddr desc_pa, int i)

{

    hwaddr pa;

    pa = desc_pa + sizeof(VRingDesc) * i + offsetof(VRingDesc, next);

    return lduw_phys(pa);

}

static inline uint16_t vring_avail_flags(VirtQueue *vq)

{

    hwaddr pa;

    pa = vq->vring.avail + offsetof(VRingAvail, flags);

    return lduw_phys(pa);

}

static inline uint16_t vring_avail_idx(VirtQueue *vq)

{

    hwaddr pa;

    pa = vq->vring.avail + offsetof(VRingAvail, idx);

    return lduw_phys(pa);

}

static inline uint16_t vring_avail_ring(VirtQueue *vq, int i)

{

    hwaddr pa;

    pa = vq->vring.avail + offsetof(VRingAvail, ring[i]);

    return lduw_phys(pa);

}

static inline uint16_t vring_used_event(VirtQueue *vq)

{

    return vring_avail_ring(vq, vq->vring.num);

}

static inline void vring_used_ring_id(VirtQueue *vq, int i, uint32_t val)

{

    hwaddr pa;

    pa = vq->vring.used + offsetof(VRingUsed, ring[i].id);

    stl_phys(pa, val);

}

static inline void vring_used_ring_len(VirtQueue *vq, int i, uint32_t val)

{

    hwaddr pa;

    pa = vq->vring.used + offsetof(VRingUsed, ring[i].len);

    stl_phys(pa, val);

}

static uint16_t vring_used_idx(VirtQueue *vq)

{

    hwaddr pa;

    pa = vq->vring.used + offsetof(VRingUsed, idx);

    return lduw_phys(pa);

}

static inline void vring_used_idx_set(VirtQueue *vq, uint16_t val)

{

    hwaddr pa;

    pa = vq->vring.used + offsetof(VRingUsed, idx);

    stw_phys(pa, val);

}

static inline void vring_used_flags_set_bit(VirtQueue *vq, int mask)

{

    hwaddr pa;

    pa = vq->vring.used + offsetof(VRingUsed, flags);

    stw_phys(pa, lduw_phys(pa) | mask);

}

static inline void vring_used_flags_unset_bit(VirtQueue *vq, int mask)

{

    hwaddr pa;

    pa = vq->vring.used + offsetof(VRingUsed, flags);

    stw_phys(pa, lduw_phys(pa) & ~mask);

}

static inline void vring_avail_event(VirtQueue *vq, uint16_t val)

{

    hwaddr pa;

    if (!vq->notification) {

        return;

    }

    pa = vq->vring.used + offsetof(VRingUsed, ring[vq->vring.num]);

    stw_phys(pa, val);

}

void virtio_queue_set_notification(VirtQueue *vq, int enable)

{

    vq->notification = enable;

    if (vq->vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) {

        vring_avail_event(vq, vring_avail_idx(vq));

    } else if (enable) {

        vring_used_flags_unset_bit(vq, VRING_USED_F_NO_NOTIFY);

    } else {

        vring_used_flags_set_bit(vq, VRING_USED_F_NO_NOTIFY);

    }

    if (enable) {

        /* Expose avail event/used flags before caller checks the avail idx. */

        smp_mb();

    }

}

int virtio_queue_ready(VirtQueue *vq)

{

    return vq->vring.avail != 0;

}

int virtio_queue_empty(VirtQueue *vq)

{

    return vring_avail_idx(vq) == vq->last_avail_idx;

}

void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,

                    unsigned int len, unsigned int idx)

{

    unsigned int offset;

    int i;

    trace_virtqueue_fill(vq, elem, len, idx);

    offset = 0;

    for (i = 0; i < elem->in_num; i++) {

        size_t size = MIN(len - offset, elem->in_sg[i].iov_len);

        cpu_physical_memory_unmap(elem->in_sg[i].iov_base,

                                  elem->in_sg[i].iov_len,

                                  1, size);

        offset += size;

    }

    for (i = 0; i < elem->out_num; i++)

        cpu_physical_memory_unmap(elem->out_sg[i].iov_base,

                                  elem->out_sg[i].iov_len,

                                  0, elem->out_sg[i].iov_len);

    idx = (idx + vring_used_idx(vq)) % vq->vring.num;

    /* Get a pointer to the next entry in the used ring. */

    vring_used_ring_id(vq, idx, elem->index);

    vring_used_ring_len(vq, idx, len);

}

void virtqueue_flush(VirtQueue *vq, unsigned int count)

{

    uint16_t old, new;

    /* Make sure buffer is written before we update index. */

    smp_wmb();

    trace_virtqueue_flush(vq, count);

    old = vring_used_idx(vq);

    new = old + count;

    vring_used_idx_set(vq, new);

    vq->inuse -= count;

    if (unlikely((int16_t)(new - vq->signalled_used) < (uint16_t)(new - old)))

        vq->signalled_used_valid = false;

}

void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,

                    unsigned int len)

{

    virtqueue_fill(vq, elem, len, 0);

    virtqueue_flush(vq, 1);

}

static int virtqueue_num_heads(VirtQueue *vq, unsigned int idx)

{

    uint16_t num_heads = vring_avail_idx(vq) - idx;

    /* Check it isn't doing very strange things with descriptor numbers. */

    if (num_heads > vq->vring.num) {

        error_report("Guest moved used index from %u to %u",

                     idx, vring_avail_idx(vq));

        exit(1);

    }

    /* On success, callers read a descriptor at vq->last_avail_idx.

     * Make sure descriptor read does not bypass avail index read. */

    if (num_heads) {

        smp_rmb();

    }

    return num_heads;

}

static unsigned int virtqueue_get_head(VirtQueue *vq, unsigned int idx)

{

    unsigned int head;

    /* Grab the next descriptor number they're advertising, and increment

     * the index we've seen. */

    head = vring_avail_ring(vq, idx % vq->vring.num);

    /* If their number is silly, that's a fatal mistake. */

    if (head >= vq->vring.num) {

        error_report("Guest says index %u is available", head);

        exit(1);

    }

    return head;

}

static unsigned virtqueue_next_desc(hwaddr desc_pa,

                                    unsigned int i, unsigned int max)

{

    unsigned int next;

    /* If this descriptor says it doesn't chain, we're done. */

    if (!(vring_desc_flags(desc_pa, i) & VRING_DESC_F_NEXT))

        return max;

    /* Check they're not leading us off end of descriptors. */

    next = vring_desc_next(desc_pa, i);

    /* Make sure compiler knows to grab that: we don't want it changing! */

    smp_wmb();

    if (next >= max) {

        error_report("Desc next is %u", next);

        exit(1);

    }

    return next;

}

void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,

                               unsigned int *out_bytes)

{

    unsigned int idx;

    unsigned int total_bufs, in_total, out_total;

    idx = vq->last_avail_idx;

    total_bufs = in_total = out_total = 0;

    while (virtqueue_num_heads(vq, idx)) {

        unsigned int max, num_bufs, indirect = 0;

        hwaddr desc_pa;

        int i;

        max = vq->vring.num;

        num_bufs = total_bufs;

        i = virtqueue_get_head(vq, idx++);

        desc_pa = vq->vring.desc;

        if (vring_desc_flags(desc_pa, i) & VRING_DESC_F_INDIRECT) {

            if (vring_desc_len(desc_pa, i) % sizeof(VRingDesc)) {

                error_report("Invalid size for indirect buffer table");

                exit(1);

            }

            /* If we've got too many, that implies a descriptor loop. */

            if (num_bufs >= max) {

                error_report("Looped descriptor");

                exit(1);

            }

            /* loop over the indirect descriptor table */

            indirect = 1;

            max = vring_desc_len(desc_pa, i) / sizeof(VRingDesc);

            num_bufs = i = 0;

            desc_pa = vring_desc_addr(desc_pa, i);

        }

        do {

            /* If we've got too many, that implies a descriptor loop. */

            if (++num_bufs > max) {

                error_report("Looped descriptor");

                exit(1);

            }

            if (vring_desc_flags(desc_pa, i) & VRING_DESC_F_WRITE) {

                in_total += vring_desc_len(desc_pa, i);

            } else {

                out_total += vring_desc_len(desc_pa, i);

            }

        } while ((i = virtqueue_next_desc(desc_pa, i, max)) != max);

        if (!indirect)

            total_bufs = num_bufs;

        else

            total_bufs++;

    }

    if (in_bytes) {

        *in_bytes = in_total;

    }

    if (out_bytes) {

        *out_bytes = out_total;

    }

}

int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes,

                          unsigned int out_bytes)

{

    unsigned int in_total, out_total;

    virtqueue_get_avail_bytes(vq, &in_total, &out_total);

    if ((in_bytes && in_bytes < in_total)

        || (out_bytes && out_bytes < out_total)) {

        return 1;

    }

    return 0;

}

void virtqueue_map_sg(struct iovec *sg, hwaddr *addr,

    size_t num_sg, int is_write)

{

    unsigned int i;

    hwaddr len;

    for (i = 0; i < num_sg; i++) {

        len = sg[i].iov_len;

        sg[i].iov_base = cpu_physical_memory_map(addr[i], &len, is_write);

        if (sg[i].iov_base == NULL || len != sg[i].iov_len) {

            error_report("virtio: trying to map MMIO memory");

            exit(1);

        }

    }

}

int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem)

{

    unsigned int i, head, max;

    hwaddr desc_pa = vq->vring.desc;

    if (!virtqueue_num_heads(vq, vq->last_avail_idx))

        return 0;

    /* When we start there are none of either input nor output. */

    elem->out_num = elem->in_num = 0;

    max = vq->vring.num;

    i = head = virtqueue_get_head(vq, vq->last_avail_idx++);

    if (vq->vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) {

        vring_avail_event(vq, vring_avail_idx(vq));

    }

    if (vring_desc_flags(desc_pa, i) & VRING_DESC_F_INDIRECT) {

        if (vring_desc_len(desc_pa, i) % sizeof(VRingDesc)) {

            error_report("Invalid size for indirect buffer table");

            exit(1);

        }

        /* loop over the indirect descriptor table */

        max = vring_desc_len(desc_pa, i) / sizeof(VRingDesc);

        desc_pa = vring_desc_addr(desc_pa, i);

        i = 0;

    }

    /* Collect all the descriptors */

    do {

        struct iovec *sg;

        if (vring_desc_flags(desc_pa, i) & VRING_DESC_F_WRITE) {

            if (elem->in_num >= ARRAY_SIZE(elem->in_sg)) {

                error_report("Too many write descriptors in indirect table");

                exit(1);

            }

            elem->in_addr[elem->in_num] = vring_desc_addr(desc_pa, i);

            sg = &elem->in_sg[elem->in_num++];

        } else {

            if (elem->out_num >= ARRAY_SIZE(elem->out_sg)) {

                error_report("Too many read descriptors in indirect table");

                exit(1);

            }

            elem->out_addr[elem->out_num] = vring_desc_addr(desc_pa, i);

            sg = &elem->out_sg[elem->out_num++];

        }

        sg->iov_len = vring_desc_len(desc_pa, i);

        /* If we've got too many, that implies a descriptor loop. */

        if ((elem->in_num + elem->out_num) > max) {

            error_report("Looped descriptor");

            exit(1);

        }

    } while ((i = virtqueue_next_desc(desc_pa, i, max)) != max);

    /* Now map what we have collected */

    virtqueue_map_sg(elem->in_sg, elem->in_addr, elem->in_num, 1);

    virtqueue_map_sg(elem->out_sg, elem->out_addr, elem->out_num, 0);

    elem->index = head;

    vq->inuse++;

    trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num);

    return elem->in_num + elem->out_num;

}

/* virtio device */

static void virtio_notify_vector(VirtIODevice *vdev, uint16_t vector)

{

    if (vdev->binding->notify) {

        vdev->binding->notify(vdev->binding_opaque, vector);

    }

}

void virtio_update_irq(VirtIODevice *vdev)

{

    virtio_notify_vector(vdev, VIRTIO_NO_VECTOR);

}

void virtio_set_status(VirtIODevice *vdev, uint8_t val)

{

    trace_virtio_set_status(vdev, val);

    if (vdev->set_status) {

        vdev->set_status(vdev, val);

    }

    vdev->status = val;

}

void virtio_reset(void *opaque)

{

    VirtIODevice *vdev = opaque;

    int i;

    virtio_set_status(vdev, 0);

    if (vdev->reset)

        vdev->reset(vdev);

    vdev->guest_features = 0;

    vdev->queue_sel = 0;

    vdev->status = 0;

    vdev->isr = 0;

    vdev->config_vector = VIRTIO_NO_VECTOR;

    virtio_notify_vector(vdev, vdev->config_vector);

    for(i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {

        vdev->vq[i].vring.desc = 0;

        vdev->vq[i].vring.avail = 0;

        vdev->vq[i].vring.used = 0;

        vdev->vq[i].last_avail_idx = 0;

        vdev->vq[i].pa = 0;

        vdev->vq[i].vector = VIRTIO_NO_VECTOR;

        vdev->vq[i].signalled_used = 0;

        vdev->vq[i].signalled_used_valid = false;

        vdev->vq[i].notification = true;

    }

}

uint32_t virtio_config_readb(VirtIODevice *vdev, uint32_t addr)

{

    uint8_t val;

    vdev->get_config(vdev, vdev->config);

    if (addr > (vdev->config_len - sizeof(val)))

        return (uint32_t)-1;

    val = ldub_p(vdev->config + addr);

    return val;

}

uint32_t virtio_config_readw(VirtIODevice *vdev, uint32_t addr)

{

    uint16_t val;

    vdev->get_config(vdev, vdev->config);

    if (addr > (vdev->config_len - sizeof(val)))

        return (uint32_t)-1;

    val = lduw_p(vdev->config + addr);

    return val;

}

uint32_t virtio_config_readl(VirtIODevice *vdev, uint32_t addr)

{

    uint32_t val;

    vdev->get_config(vdev, vdev->config);

    if (addr > (vdev->config_len - sizeof(val)))

        return (uint32_t)-1;

    val = ldl_p(vdev->config + addr);

    return val;

}

void virtio_config_writeb(VirtIODevice *vdev, uint32_t addr, uint32_t data)

{

    uint8_t val = data;

    if (addr > (vdev->config_len - sizeof(val)))

        return;

    stb_p(vdev->config + addr, val);

    if (vdev->set_config)

        vdev->set_config(vdev, vdev->config);

}

void virtio_config_writew(VirtIODevice *vdev, uint32_t addr, uint32_t data)

{

    uint16_t val = data;

    if (addr > (vdev->config_len - sizeof(val)))

        return;

    stw_p(vdev->config + addr, val);

    if (vdev->set_config)

        vdev->set_config(vdev, vdev->config);

}

void virtio_config_writel(VirtIODevice *vdev, uint32_t addr, uint32_t data)

{

    uint32_t val = data;

    if (addr > (vdev->config_len - sizeof(val)))

        return;

    stl_p(vdev->config + addr, val);

    if (vdev->set_config)

        vdev->set_config(vdev, vdev->config);

}

void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr)

{

    vdev->vq[n].pa = addr;

    virtqueue_init(&vdev->vq[n]);

}

hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n)

{

    return vdev->vq[n].pa;

}

int virtio_queue_get_num(VirtIODevice *vdev, int n)

{

    return vdev->vq[n].vring.num;

}

int virtio_queue_get_id(VirtQueue *vq)

{

    VirtIODevice *vdev = vq->vdev;

    assert(vq >= &vdev->vq[0] && vq < &vdev->vq[VIRTIO_PCI_QUEUE_MAX]);

    return vq - &vdev->vq[0];

}

void virtio_queue_notify_vq(VirtQueue *vq)

{

    if (vq->vring.desc) {

        VirtIODevice *vdev = vq->vdev;

        trace_virtio_queue_notify(vdev, vq - vdev->vq, vq);

        vq->handle_output(vdev, vq);

    }

}

void virtio_queue_notify(VirtIODevice *vdev, int n)

{

    virtio_queue_notify_vq(&vdev->vq[n]);

}

uint16_t virtio_queue_vector(VirtIODevice *vdev, int n)

{

    return n < VIRTIO_PCI_QUEUE_MAX ? vdev->vq[n].vector :

        VIRTIO_NO_VECTOR;

}

void virtio_queue_set_vector(VirtIODevice *vdev, int n, uint16_t vector)

{

    if (n < VIRTIO_PCI_QUEUE_MAX)

        vdev->vq[n].vector = vector;

}

VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,

                            void (*handle_output)(VirtIODevice *, VirtQueue *))

{

    int i;

    for (i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {

        if (vdev->vq[i].vring.num == 0)

            break;

    }

    if (i == VIRTIO_PCI_QUEUE_MAX || queue_size > VIRTQUEUE_MAX_SIZE)

        abort();

    vdev->vq[i].vring.num = queue_size;

    vdev->vq[i].handle_output = handle_output;

    return &vdev->vq[i];

}

void virtio_irq(VirtQueue *vq)

{

    trace_virtio_irq(vq);

    vq->vdev->isr |= 0x01;

    virtio_notify_vector(vq->vdev, vq->vector);

}

/* Assuming a given event_idx value from the other size, if

 * we have just incremented index from old to new_idx,

 * should we trigger an event? */

static inline int vring_need_event(uint16_t event, uint16_t new, uint16_t old)

{

        /* Note: Xen has similar logic for notification hold-off

         * in include/xen/interface/io/ring.h with req_event and req_prod

         * corresponding to event_idx + 1 and new respectively.

         * Note also that req_event and req_prod in Xen start at 1,

         * event indexes in virtio start at 0. */

        return (uint16_t)(new - event - 1) < (uint16_t)(new - old);

}

static bool vring_notify(VirtIODevice *vdev, VirtQueue *vq)

{

    uint16_t old, new;

    bool v;

    /* We need to expose used array entries before checking used event. */

    smp_mb();

    /* Always notify when queue is empty (when feature acknowledge) */

    if (((vdev->guest_features & (1 << VIRTIO_F_NOTIFY_ON_EMPTY)) &&

         !vq->inuse && vring_avail_idx(vq) == vq->last_avail_idx)) {

        return true;

    }

    if (!(vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX))) {

        return !(vring_avail_flags(vq) & VRING_AVAIL_F_NO_INTERRUPT);

    }

    v = vq->signalled_used_valid;

    vq->signalled_used_valid = true;

    old = vq->signalled_used;

    new = vq->signalled_used = vring_used_idx(vq);

    return !v || vring_need_event(vring_used_event(vq), new, old);

}

void virtio_notify(VirtIODevice *vdev, VirtQueue *vq)

{

    if (!vring_notify(vdev, vq)) {

        return;

    }

    trace_virtio_notify(vdev, vq);

    vdev->isr |= 0x01;

    virtio_notify_vector(vdev, vq->vector);

}

void virtio_notify_config(VirtIODevice *vdev)

{

    if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK))

        return;

    vdev->isr |= 0x03;

    virtio_notify_vector(vdev, vdev->config_vector);

}

void virtio_save(VirtIODevice *vdev, QEMUFile *f)

{

    int i;

    if (vdev->binding->save_config)

        vdev->binding->save_config(vdev->binding_opaque, f);

    qemu_put_8s(f, &vdev->status);

    qemu_put_8s(f, &vdev->isr);

    qemu_put_be16s(f, &vdev->queue_sel);

    qemu_put_be32s(f, &vdev->guest_features);

    qemu_put_be32(f, vdev->config_len);

    qemu_put_buffer(f, vdev->config, vdev->config_len);

    for (i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {

        if (vdev->vq[i].vring.num == 0)

            break;

    }

    qemu_put_be32(f, i);

    for (i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {

        if (vdev->vq[i].vring.num == 0)

            break;

        qemu_put_be32(f, vdev->vq[i].vring.num);

        qemu_put_be64(f, vdev->vq[i].pa);

        qemu_put_be16s(f, &vdev->vq[i].last_avail_idx);

        if (vdev->binding->save_queue)

            vdev->binding->save_queue(vdev->binding_opaque, i, f);

    }

}

int virtio_set_features(VirtIODevice *vdev, uint32_t val)

{

    uint32_t supported_features =

        vdev->binding->get_features(vdev->binding_opaque);

    bool bad = (val & ~supported_features) != 0;

    val &= supported_features;

    if (vdev->set_features) {

        vdev->set_features(vdev, val);

    }

    vdev->guest_features = val;

    return bad ? -1 : 0;

}

int virtio_load(VirtIODevice *vdev, QEMUFile *f)

{

    int num, i, ret;

    uint32_t features;

    uint32_t supported_features;

    if (vdev->binding->load_config) {

        ret = vdev->binding->load_config(vdev->binding_opaque, f);

        if (ret)

            return ret;

    }

    qemu_get_8s(f, &vdev->status);

    qemu_get_8s(f, &vdev->isr);

    qemu_get_be16s(f, &vdev->queue_sel);

    qemu_get_be32s(f, &features);

    if (virtio_set_features(vdev, features) < 0) {

        supported_features = vdev->binding->get_features(vdev->binding_opaque);

        error_report("Features 0x%x unsupported. Allowed features: 0x%x",

                     features, supported_features);

        return -1;

    }

    vdev->config_len = qemu_get_be32(f);

    qemu_get_buffer(f, vdev->config, vdev->config_len);

    num = qemu_get_be32(f);

    for (i = 0; i < num; i++) {

        vdev->vq[i].vring.num = qemu_get_be32(f);

        vdev->vq[i].pa = qemu_get_be64(f);

        qemu_get_be16s(f, &vdev->vq[i].last_avail_idx);

        vdev->vq[i].signalled_used_valid = false;

        vdev->vq[i].notification = true;

        if (vdev->vq[i].pa) {

            uint16_t nheads;

            virtqueue_init(&vdev->vq[i]);

            nheads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx;

            /* Check it isn't doing very strange things with descriptor numbers. */

            if (nheads > vdev->vq[i].vring.num) {

                error_report("VQ %d size 0x%x Guest index 0x%x "

                             "inconsistent with Host index 0x%x: delta 0x%x",

                             i, vdev->vq[i].vring.num,

                             vring_avail_idx(&vdev->vq[i]),

                             vdev->vq[i].last_avail_idx, nheads);

                return -1;

            }

        } else if (vdev->vq[i].last_avail_idx) {

            error_report("VQ %d address 0x0 "

                         "inconsistent with Host index 0x%x",

                         i, vdev->vq[i].last_avail_idx);

                return -1;

        }

        if (vdev->binding->load_queue) {

            ret = vdev->binding->load_queue(vdev->binding_opaque, i, f);

            if (ret)

                return ret;

        }

    }

    virtio_notify_vector(vdev, VIRTIO_NO_VECTOR);

    return 0;

}

void virtio_cleanup(VirtIODevice *vdev)

{

    qemu_del_vm_change_state_handler(vdev->vmstate);

    g_free(vdev->config);

    g_free(vdev->vq);

    g_free(vdev);

}

static void virtio_vmstate_change(void *opaque, int running, RunState state)

{

    VirtIODevice *vdev = opaque;

    bool backend_run = running && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK);

    vdev->vm_running = running;

    if (backend_run) {

        virtio_set_status(vdev, vdev->status);

    }

    if (vdev->binding->vmstate_change) {

        vdev->binding->vmstate_change(vdev->binding_opaque, backend_run);

    }

    if (!backend_run) {

        virtio_set_status(vdev, vdev->status);

    }

}

VirtIODevice *virtio_common_init(const char *name, uint16_t device_id,

                                 size_t config_size, size_t struct_size)

{

    VirtIODevice *vdev;

    int i;

    vdev = g_malloc0(struct_size);

    vdev->device_id = device_id;

    vdev->status = 0;

    vdev->isr = 0;

    vdev->queue_sel = 0;

    vdev->config_vector = VIRTIO_NO_VECTOR;

    vdev->vq = g_malloc0(sizeof(VirtQueue) * VIRTIO_PCI_QUEUE_MAX);

    vdev->vm_running = runstate_is_running();

    for(i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {

        vdev->vq[i].vector = VIRTIO_NO_VECTOR;

        vdev->vq[i].vdev = vdev;

    }