diff mbox series

[v1,13/16] virtio: add vhost-net migration of packed ring

Message ID 1542895581-10721-14-git-send-email-wexu@redhat.com (mailing list archive)
State New, archived
Headers show
Series packed ring virtio-net backend support | expand

Commit Message

Wei Xu Nov. 22, 2018, 2:06 p.m. UTC 
From: Wei Xu <wexu@redhat.com>

tweaked vhost-net code to test migration.

@@ -1414,64 +1430,20 @@ long vhost_vring_ioctl(struct vhost_dev
            r = -EFAULT;
            break;
        }
+               vq->last_avail_idx = s.num & 0x7FFF;
+               /* Forget the cached index value. */
+               vq->avail_idx = vq->last_avail_idx;
+               if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+                       vq->last_avail_wrap_counter = !!(s.num & 0x8000);
+                       vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+
+                       vq->last_used_idx = (s.num & 0x7fFF0000) >> 16;
+                       vq->last_used_wrap_counter = !!(s.num & 0x80000000);
+               }
+               break;
+       case VHOST_GET_VRING_BASE:
+               s.index = idx;
+                s.num = vq->last_avail_idx;
+               if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+                       s.num |= vq->last_avail_wrap_counter << 15;
+                       s.num |= vq->last_used_idx << 16;
+                       s.num |= vq->last_used_wrap_counter << 31;
+               }
+               if (copy_to_user(argp, &s, sizeof(s)))
+                       r = -EFAULT;
+               break;

Signed-off-by: Wei Xu <wexu@redhat.com>
---
 hw/virtio/virtio.c         | 35 ++++++++++++++++++++++++++++++-----
 include/hw/virtio/virtio.h |  4 ++--
 2 files changed, 32 insertions(+), 7 deletions(-)

Comments

Maxime Coquelin Nov. 28, 2018, 10:05 a.m. UTC | #1 
On 11/22/18 3:06 PM, wexu@redhat.com wrote:
> From: Wei Xu <wexu@redhat.com>
> 
> tweaked vhost-net code to test migration.
> 
> @@ -1414,64 +1430,20 @@ long vhost_vring_ioctl(struct vhost_dev
>              r = -EFAULT;
>              break;
>          }
> +               vq->last_avail_idx = s.num & 0x7FFF;
> +               /* Forget the cached index value. */
> +               vq->avail_idx = vq->last_avail_idx;
> +               if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
> +                       vq->last_avail_wrap_counter = !!(s.num & 0x8000);
> +                       vq->avail_wrap_counter = vq->last_avail_wrap_counter;
> +
> +                       vq->last_used_idx = (s.num & 0x7fFF0000) >> 16;
> +                       vq->last_used_wrap_counter = !!(s.num & 0x80000000);
> +               }
> +               break;
> +       case VHOST_GET_VRING_BASE:
> +               s.index = idx;
> +                s.num = vq->last_avail_idx;
> +               if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
> +                       s.num |= vq->last_avail_wrap_counter << 15;
> +                       s.num |= vq->last_used_idx << 16;
> +                       s.num |= vq->last_used_wrap_counter << 31;

We agreed to only have avail idx and its wrap counter for vhost-user,
I guess we should have the same for Kernel backend?

This is what we have for vhost-user backend:
bit[0:14] last_avail_idx
bit[15] last_avail_wrap_counter

> +               }
> +               if (copy_to_user(argp, &s, sizeof(s)))
> +                       r = -EFAULT;
> +               break;
> 
> Signed-off-by: Wei Xu <wexu@redhat.com>
> ---
>   hw/virtio/virtio.c         | 35 ++++++++++++++++++++++++++++++-----
>   include/hw/virtio/virtio.h |  4 ++--
>   2 files changed, 32 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 64d5c04..7487d3d 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2963,19 +2963,40 @@ hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n)
>       }
>   }
>   
> -uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
> +int virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
>   {
> -    return vdev->vq[n].last_avail_idx;
> +    int idx;
> +
> +    if (virtio_host_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> +        idx = vdev->vq[n].last_avail_idx;
> +        idx |= ((int)vdev->vq[n].avail_wrap_counter) << 15;
> +        idx |= (vdev->vq[n].used_idx) << 16;
> +        idx |= ((int)vdev->vq[n].used_wrap_counter) << 31;
> +    } else {
> +        idx = (int)vdev->vq[n].last_avail_idx;
> +    }
> +    return idx;
>   }
>   
> -void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)
> +void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, int idx)
>   {
> -    vdev->vq[n].last_avail_idx = idx;
> -    vdev->vq[n].shadow_avail_idx = idx;
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> +        vdev->vq[n].last_avail_idx = idx & 0x7fff;
> +        vdev->vq[n].avail_wrap_counter = !!(idx & 0x8000);
> +        vdev->vq[n].used_idx = (idx & 0x7fff0000) >> 16;
> +        vdev->vq[n].used_wrap_counter = !!(idx & 0x80000000);
> +    } else {
> +        vdev->vq[n].last_avail_idx = idx;
> +        vdev->vq[n].shadow_avail_idx = idx;
> +    }
>   }
>   
>   void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
>   {
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> +        return;
> +    }
> +
>       rcu_read_lock();
>       if (vdev->vq[n].vring.desc) {
>           vdev->vq[n].last_avail_idx = vring_used_idx(&vdev->vq[n]);
> @@ -2986,6 +3007,10 @@ void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
>   
>   void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
>   {
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> +        return;
> +    }
> +
>       rcu_read_lock();
>       if (vdev->vq[n].vring.desc) {
>           vdev->vq[n].used_idx = vring_used_idx(&vdev->vq[n]);
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index 9c1fa07..a6fdf3f 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -272,8 +272,8 @@ hwaddr virtio_queue_get_used_addr(VirtIODevice *vdev, int n);
>   hwaddr virtio_queue_get_desc_size(VirtIODevice *vdev, int n);
>   hwaddr virtio_queue_get_avail_size(VirtIODevice *vdev, int n);
>   hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n);
> -uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
> -void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx);
> +int virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
> +void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, int idx);
>   void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n);
>   void virtio_queue_invalidate_signalled_used(VirtIODevice *vdev, int n);
>   void virtio_queue_update_used_idx(VirtIODevice *vdev, int n);
>
Maxime Coquelin Nov. 28, 2018, 10:34 a.m. UTC | #2 
On 11/22/18 3:06 PM, wexu@redhat.com wrote:
> From: Wei Xu <wexu@redhat.com>
> 
> tweaked vhost-net code to test migration.
> 
> @@ -1414,64 +1430,20 @@ long vhost_vring_ioctl(struct vhost_dev
>              r = -EFAULT;
>              break;
>          }
> +               vq->last_avail_idx = s.num & 0x7FFF;
> +               /* Forget the cached index value. */
> +               vq->avail_idx = vq->last_avail_idx;
> +               if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
> +                       vq->last_avail_wrap_counter = !!(s.num & 0x8000);
> +                       vq->avail_wrap_counter = vq->last_avail_wrap_counter;
> +
> +                       vq->last_used_idx = (s.num & 0x7fFF0000) >> 16;
> +                       vq->last_used_wrap_counter = !!(s.num & 0x80000000);
> +               }
> +               break;
> +       case VHOST_GET_VRING_BASE:
> +               s.index = idx;
> +                s.num = vq->last_avail_idx;
> +               if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
> +                       s.num |= vq->last_avail_wrap_counter << 15;
> +                       s.num |= vq->last_used_idx << 16;
> +                       s.num |= vq->last_used_wrap_counter << 31;
> +               }
> +               if (copy_to_user(argp, &s, sizeof(s)))
> +                       r = -EFAULT;
> +               break;
> 
> Signed-off-by: Wei Xu <wexu@redhat.com>
> ---
>   hw/virtio/virtio.c         | 35 ++++++++++++++++++++++++++++++-----
>   include/hw/virtio/virtio.h |  4 ++--
>   2 files changed, 32 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 64d5c04..7487d3d 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2963,19 +2963,40 @@ hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n)
>       }
>   }
>   
> -uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
> +int virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
>   {
> -    return vdev->vq[n].last_avail_idx;
> +    int idx;
> +
> +    if (virtio_host_has_feature(vdev, VIRTIO_F_RING_PACKED)) {

Also, I think you want to use virtio_vdev_has_feature() here instead,
else it will set wrap counter in the case ring_packed=on in the QEMU
command line but the feature has not been negotiated.


For example, with ring_packed=on and with stock Fedora 28 kernel, which
does not support packed ring, I get this warning with DPDK vhost user
backend:

VHOST_CONFIG: last_used_idx (32768) and vq->used->idx (0) mismatches;
some packets maybe resent for Tx and dropped for Rx

> +        idx = vdev->vq[n].last_avail_idx;
> +        idx |= ((int)vdev->vq[n].avail_wrap_counter) << 15;
> +        idx |= (vdev->vq[n].used_idx) << 16;
> +        idx |= ((int)vdev->vq[n].used_wrap_counter) << 31;
> +    } else {
> +        idx = (int)vdev->vq[n].last_avail_idx;
> +    }
> +    return idx;
>   }
>   
> -void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)
> +void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, int idx)
>   {
> -    vdev->vq[n].last_avail_idx = idx;
> -    vdev->vq[n].shadow_avail_idx = idx;
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> +        vdev->vq[n].last_avail_idx = idx & 0x7fff;
> +        vdev->vq[n].avail_wrap_counter = !!(idx & 0x8000);
> +        vdev->vq[n].used_idx = (idx & 0x7fff0000) >> 16;
> +        vdev->vq[n].used_wrap_counter = !!(idx & 0x80000000);
> +    } else {
> +        vdev->vq[n].last_avail_idx = idx;
> +        vdev->vq[n].shadow_avail_idx = idx;
> +    }
>   }
>   
>   void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
>   {
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> +        return;
> +    }
> +
>       rcu_read_lock();
>       if (vdev->vq[n].vring.desc) {
>           vdev->vq[n].last_avail_idx = vring_used_idx(&vdev->vq[n]);
> @@ -2986,6 +3007,10 @@ void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
>   
>   void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
>   {
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> +        return;
> +    }
> +
>       rcu_read_lock();
>       if (vdev->vq[n].vring.desc) {
>           vdev->vq[n].used_idx = vring_used_idx(&vdev->vq[n]);
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index 9c1fa07..a6fdf3f 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -272,8 +272,8 @@ hwaddr virtio_queue_get_used_addr(VirtIODevice *vdev, int n);
>   hwaddr virtio_queue_get_desc_size(VirtIODevice *vdev, int n);
>   hwaddr virtio_queue_get_avail_size(VirtIODevice *vdev, int n);
>   hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n);
> -uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
> -void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx);
> +int virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
> +void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, int idx);
>   void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n);
>   void virtio_queue_invalidate_signalled_used(VirtIODevice *vdev, int n);
>   void virtio_queue_update_used_idx(VirtIODevice *vdev, int n);
>
Wei Xu Jan. 16, 2019, 5:48 p.m. UTC | #3 
On Wed, Nov 28, 2018 at 11:34:46AM +0100, Maxime Coquelin wrote:
> 
> 
> On 11/22/18 3:06 PM, wexu@redhat.com wrote:
> >From: Wei Xu <wexu@redhat.com>
> >
> >tweaked vhost-net code to test migration.
> >
> >@@ -1414,64 +1430,20 @@ long vhost_vring_ioctl(struct vhost_dev
> >             r = -EFAULT;
> >             break;
> >         }
> >+               vq->last_avail_idx = s.num & 0x7FFF;
> >+               /* Forget the cached index value. */
> >+               vq->avail_idx = vq->last_avail_idx;
> >+               if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
> >+                       vq->last_avail_wrap_counter = !!(s.num & 0x8000);
> >+                       vq->avail_wrap_counter = vq->last_avail_wrap_counter;
> >+
> >+                       vq->last_used_idx = (s.num & 0x7fFF0000) >> 16;
> >+                       vq->last_used_wrap_counter = !!(s.num & 0x80000000);
> >+               }
> >+               break;
> >+       case VHOST_GET_VRING_BASE:
> >+               s.index = idx;
> >+                s.num = vq->last_avail_idx;
> >+               if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
> >+                       s.num |= vq->last_avail_wrap_counter << 15;
> >+                       s.num |= vq->last_used_idx << 16;
> >+                       s.num |= vq->last_used_wrap_counter << 31;
> >+               }
> >+               if (copy_to_user(argp, &s, sizeof(s)))
> >+                       r = -EFAULT;
> >+               break;
> >
> >Signed-off-by: Wei Xu <wexu@redhat.com>
> >---
> >  hw/virtio/virtio.c         | 35 ++++++++++++++++++++++++++++++-----
> >  include/hw/virtio/virtio.h |  4 ++--
> >  2 files changed, 32 insertions(+), 7 deletions(-)
> >
> >diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >index 64d5c04..7487d3d 100644
> >--- a/hw/virtio/virtio.c
> >+++ b/hw/virtio/virtio.c
> >@@ -2963,19 +2963,40 @@ hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n)
> >      }
> >  }
> >-uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
> >+int virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
> >  {
> >-    return vdev->vq[n].last_avail_idx;
> >+    int idx;
> >+
> >+    if (virtio_host_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> 
> Also, I think you want to use virtio_vdev_has_feature() here instead,
> else it will set wrap counter in the case ring_packed=on in the QEMU
> command line but the feature has not been negotiated.
> 
> 
> For example, with ring_packed=on and with stock Fedora 28 kernel, which
> does not support packed ring, I get this warning with DPDK vhost user
> backend:
> 
> VHOST_CONFIG: last_used_idx (32768) and vq->used->idx (0) mismatches;
> some packets maybe resent for Tx and dropped for Rx

Thanks, will fix it.

Wei

> 
> >+        idx = vdev->vq[n].last_avail_idx;
> >+        idx |= ((int)vdev->vq[n].avail_wrap_counter) << 15;
> >+        idx |= (vdev->vq[n].used_idx) << 16;
> >+        idx |= ((int)vdev->vq[n].used_wrap_counter) << 31;
> >+    } else {
> >+        idx = (int)vdev->vq[n].last_avail_idx;
> >+    }
> >+    return idx;
> >  }
> >-void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)
> >+void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, int idx)
> >  {
> >-    vdev->vq[n].last_avail_idx = idx;
> >-    vdev->vq[n].shadow_avail_idx = idx;
> >+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> >+        vdev->vq[n].last_avail_idx = idx & 0x7fff;
> >+        vdev->vq[n].avail_wrap_counter = !!(idx & 0x8000);
> >+        vdev->vq[n].used_idx = (idx & 0x7fff0000) >> 16;
> >+        vdev->vq[n].used_wrap_counter = !!(idx & 0x80000000);
> >+    } else {
> >+        vdev->vq[n].last_avail_idx = idx;
> >+        vdev->vq[n].shadow_avail_idx = idx;
> >+    }
> >  }
> >  void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
> >  {
> >+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> >+        return;
> >+    }
> >+
> >      rcu_read_lock();
> >      if (vdev->vq[n].vring.desc) {
> >          vdev->vq[n].last_avail_idx = vring_used_idx(&vdev->vq[n]);
> >@@ -2986,6 +3007,10 @@ void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
> >  void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
> >  {
> >+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
> >+        return;
> >+    }
> >+
> >      rcu_read_lock();
> >      if (vdev->vq[n].vring.desc) {
> >          vdev->vq[n].used_idx = vring_used_idx(&vdev->vq[n]);
> >diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> >index 9c1fa07..a6fdf3f 100644
> >--- a/include/hw/virtio/virtio.h
> >+++ b/include/hw/virtio/virtio.h
> >@@ -272,8 +272,8 @@ hwaddr virtio_queue_get_used_addr(VirtIODevice *vdev, int n);
> >  hwaddr virtio_queue_get_desc_size(VirtIODevice *vdev, int n);
> >  hwaddr virtio_queue_get_avail_size(VirtIODevice *vdev, int n);
> >  hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n);
> >-uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
> >-void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx);
> >+int virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
> >+void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, int idx);
> >  void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n);
> >  void virtio_queue_invalidate_signalled_used(VirtIODevice *vdev, int n);
> >  void virtio_queue_update_used_idx(VirtIODevice *vdev, int n);
> >
diff mbox series

Patch

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 64d5c04..7487d3d 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2963,19 +2963,40 @@  hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n)
     }
 }
 
-uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
+int virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n)
 {
-    return vdev->vq[n].last_avail_idx;
+    int idx;
+
+    if (virtio_host_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+        idx = vdev->vq[n].last_avail_idx;
+        idx |= ((int)vdev->vq[n].avail_wrap_counter) << 15;
+        idx |= (vdev->vq[n].used_idx) << 16;
+        idx |= ((int)vdev->vq[n].used_wrap_counter) << 31;
+    } else {
+        idx = (int)vdev->vq[n].last_avail_idx;
+    }
+    return idx;
 }
 
-void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)
+void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, int idx)
 {
-    vdev->vq[n].last_avail_idx = idx;
-    vdev->vq[n].shadow_avail_idx = idx;
+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+        vdev->vq[n].last_avail_idx = idx & 0x7fff;
+        vdev->vq[n].avail_wrap_counter = !!(idx & 0x8000);
+        vdev->vq[n].used_idx = (idx & 0x7fff0000) >> 16;
+        vdev->vq[n].used_wrap_counter = !!(idx & 0x80000000);
+    } else {
+        vdev->vq[n].last_avail_idx = idx;
+        vdev->vq[n].shadow_avail_idx = idx;
+    }
 }
 
 void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
 {
+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+        return;
+    }
+
     rcu_read_lock();
     if (vdev->vq[n].vring.desc) {
         vdev->vq[n].last_avail_idx = vring_used_idx(&vdev->vq[n]);
@@ -2986,6 +3007,10 @@  void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
 
 void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
 {
+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
+        return;
+    }
+
     rcu_read_lock();
     if (vdev->vq[n].vring.desc) {
         vdev->vq[n].used_idx = vring_used_idx(&vdev->vq[n]);
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 9c1fa07..a6fdf3f 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -272,8 +272,8 @@  hwaddr virtio_queue_get_used_addr(VirtIODevice *vdev, int n);
 hwaddr virtio_queue_get_desc_size(VirtIODevice *vdev, int n);
 hwaddr virtio_queue_get_avail_size(VirtIODevice *vdev, int n);
 hwaddr virtio_queue_get_used_size(VirtIODevice *vdev, int n);
-uint16_t virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
-void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx);
+int virtio_queue_get_last_avail_idx(VirtIODevice *vdev, int n);
+void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, int idx);
 void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n);
 void virtio_queue_invalidate_signalled_used(VirtIODevice *vdev, int n);
 void virtio_queue_update_used_idx(VirtIODevice *vdev, int n);