On Mon, Oct 19, 2015 at 02:59:27PM +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 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 queue index is computed by taking account of the vq_index (to retrieve the
> queue pair index) and calling the vhost_get_vq_index method of the backend.
>
> Signed-off-by: Thibaut Collet <thibaut.col...@6wind.com>
Thanks!
The code in question was added by:
commit a9f98bb5ebe6fb1869321dcc58e72041ae626ad8
Author: Jason Wang <jasow...@redhat.com>
Date: Wed Jan 30 19:12:35 2013 +0800
vhost: multiqueue support
Jason, could you comment on whether this makes sense please?
If yes - this is an old bug, and we need this on stable,
do we not?
Maybe we should refactor vhost_virtqueue_set_addr to
make it call vhost_get_vq_index internally automatically.
All callers do this anyway.
This can be a patch on top.
> ---
> hw/virtio/vhost.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index feeaaa4..de29968 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -656,13 +656,14 @@ static int vhost_dev_set_features(struct vhost_dev
> *dev, bool enable_log)
>
> static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log)
> {
> - int r, t, i;
> + int r, t, i, idx;
> r = vhost_dev_set_features(dev, enable_log);
> if (r < 0) {
> goto err_features;
> }
> for (i = 0; i < dev->nvqs; ++i) {
> - r = vhost_virtqueue_set_addr(dev, dev->vqs + i, i,
> + idx = dev->vhost_ops->vhost_get_vq_index(dev, dev->vq_index + i);
> + r = vhost_virtqueue_set_addr(dev, dev->vqs + i, idx,
> enable_log);
> if (r < 0) {
> goto err_vq;
> @@ -671,7 +672,8 @@ 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,
> + idx = dev->vhost_ops->vhost_get_vq_index(dev, dev->vq_index + i);
> + t = vhost_virtqueue_set_addr(dev, dev->vqs + i, idx,
> dev->log_enabled);
> assert(t >= 0);
> }
> --
> 2.1.4
