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virtio: Add queue interface to restore avail index from vring used index

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In case of backend crash, it is not possible to restore internal
avail index from the backend value as vhost_get_vring_base
callback fails.

This patch provides a new interface to restore internal avail index
from the vring used index, as done by some vhost-user backend on
reconnection.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Maxime Coquelin 2017-11-16 19:48:34 +01:00 committed by Michael S. Tsirkin
parent 861fec459b
commit 2d4ba6cc74
2 changed files with 11 additions and 0 deletions
hw/virtio
virtio.c
include/hw/virtio
virtio.h

10
hw/virtio/virtio.c

@ -2310,6 +2310,16 @@ void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)
vdev->vq[n].shadow_avail_idx = idx;
}
void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
{
rcu_read_lock();
if (vdev->vq[n].vring.desc) {
vdev->vq[n].last_avail_idx = vring_used_idx(&vdev->vq[n]);
vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
}
rcu_read_unlock();
}
void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
{
rcu_read_lock();

1
include/hw/virtio/virtio.h

@ -272,6 +272,7 @@ 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);
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);
VirtQueue *virtio_get_queue(VirtIODevice *vdev, int n);