Re: [PATCH 7/7] vhost-vdpa: backend feature should set only once

[Jason Wang]

On Wed, Mar 30, 2022 at 2:33 PM Si-Wei Liu <si-wei.liu@oracle.com> wrote:
>
> The vhost_vdpa_one_time_request() branch in
> vhost_vdpa_set_backend_cap() incorrectly sends down
> iotls on vhost_dev with non-zero index. This may
> end up with multiple VHOST_SET_BACKEND_FEATURES
> ioctl calls sent down on the vhost-vdpa fd that is
> shared between all these vhost_dev's.
>
> To fix it, send down ioctl only once via the first
> vhost_dev with index 0. Toggle the polarity of the
> vhost_vdpa_one_time_request() test would do the trick.
>
> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>

Acked-by: Jason Wang <jasowang@redhat.com>

> ---
>  hw/virtio/vhost-vdpa.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index c5ed7a3..27ea706 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -665,7 +665,7 @@ static int vhost_vdpa_set_backend_cap(struct vhost_dev 
> *dev)
>
>      features &= f;
>
> -    if (vhost_vdpa_one_time_request(dev)) {
> +    if (!vhost_vdpa_one_time_request(dev)) {
>          r = vhost_vdpa_call(dev, VHOST_SET_BACKEND_FEATURES, &features);
>          if (r) {
>              return -EFAULT;
> --
> 1.8.3.1
>