Re: [Qemu-devel] [PATCH v2 1/1] vhost: set the correct queue index in case of migration with multiqueue

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Oct 21, 2015 at 11:19:14AM +0200, Thibaut Collet wrote:
> When a live migration is started the log address to mark dirty pages is provided
> to the vhost backend through the vhost_dev_set_log function.
> This function is called for each queue pairs but the queue index provided to the
> vhost_virtqueue_set_addr function is wrongly set: always set to the first queue
> pair. Then vhost backend lost descriptor addresses of the queue pairs greater
> than 1 and behaviour of the vhost backend is unpredictable.
> 
> The vhost_dev_set_log is modified to provide the correct queue index to the
> vhost_virtqueue_set_addr function that calls internally the vhost_get_vq_index
> to compute the expected vhost_vq_index for vhost kernel and vhost user.
> This change implies a modification of the vhost_virtqueue_start function to
> provide the index and not the vhost_vq_index.
> 
> Signed-off-by: Thibaut Collet <thibaut.collet@6wind.com>

I applied v1 already, please post a patch on top.

> ---
>  hw/virtio/vhost.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index feeaaa4..9311832 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -628,8 +628,9 @@ static int vhost_virtqueue_set_addr(struct vhost_dev *dev,
>                                      struct vhost_virtqueue *vq,
>                                      unsigned idx, bool enable_log)
>  {
> +    int vhost_vq_index = dev->vhost_ops->vhost_get_vq_index(dev, idx);
>      struct vhost_vring_addr addr = {
> -        .index = idx,
> +        .index = vhost_vq_index,
>          .desc_user_addr = (uint64_t)(unsigned long)vq->desc,
>          .avail_user_addr = (uint64_t)(unsigned long)vq->avail,
>          .used_user_addr = (uint64_t)(unsigned long)vq->used,
> @@ -662,7 +663,7 @@ static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log)
>          goto err_features;
>      }
>      for (i = 0; i < dev->nvqs; ++i) {
> -        r = vhost_virtqueue_set_addr(dev, dev->vqs + i, i,
> +        r = vhost_virtqueue_set_addr(dev, dev->vqs + i, dev->vq_index + i,
>                                       enable_log);
>          if (r < 0) {
>              goto err_vq;
> @@ -671,7 +672,7 @@ static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log)
>      return 0;
>  err_vq:
>      for (; i >= 0; --i) {
> -        t = vhost_virtqueue_set_addr(dev, dev->vqs + i, i,
> +        t = vhost_virtqueue_set_addr(dev, dev->vqs + i, dev->vq_index + i,
>                                       dev->log_enabled);
>          assert(t >= 0);
>      }
> @@ -836,7 +837,7 @@ static int vhost_virtqueue_start(struct vhost_dev *dev,
>          goto fail_alloc_ring;
>      }
>  
> -    r = vhost_virtqueue_set_addr(dev, vq, vhost_vq_index, dev->log_enabled);
> +    r = vhost_virtqueue_set_addr(dev, vq, idx, dev->log_enabled);
>      if (r < 0) {
>          r = -errno;
>          goto fail_alloc;
> -- 
> 2.1.4