Re: [PATCH] vhost: fix vring enable with VDPA

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 3/2/23 10:48, David Marchand wrote:
> For VDPA devices, vq are not locked once the device has been configured.
> But we need to hold the vq lock to check if vhost async is enabled.
> 
> Combining VDPA and vhost async does not seem to make much sense, so
> prevent this combination, and only assert the lock is taken when VDPA is
> not configured on this vq.
> 
> Bugzilla ID: 1169
> Fixes: 4b02c2673757 ("vhost: annotate async accesses")
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
>   lib/vhost/vhost.c      | 4 ++--
>   lib/vhost/vhost_user.c | 8 ++++----
>   2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
> index c36dc06a0a..6b73c03224 100644
> --- a/lib/vhost/vhost.c
> +++ b/lib/vhost/vhost.c
> @@ -1754,7 +1754,7 @@ rte_vhost_async_channel_register(int vid, uint16_t queue_id)
>   
>   	vq = dev->virtqueue[queue_id];
>   
> -	if (unlikely(vq == NULL || !dev->async_copy))
> +	if (unlikely(vq == NULL || !dev->async_copy || dev->vdpa_dev))
>   		return -1;
>   
>   	rte_spinlock_lock(&vq->access_lock);
> @@ -1778,7 +1778,7 @@ rte_vhost_async_channel_register_thread_unsafe(int vid, uint16_t queue_id)
>   
>   	vq = dev->virtqueue[queue_id];
>   
> -	if (unlikely(vq == NULL || !dev->async_copy))
> +	if (unlikely(vq == NULL || !dev->async_copy || dev->vdpa_dev))
>   		return -1;
>   
>   	vq_assert_lock(dev, vq);
> diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
> index d702d082dd..daf3458985 100644
> --- a/lib/vhost/vhost_user.c
> +++ b/lib/vhost/vhost_user.c
> @@ -2177,10 +2177,10 @@ vhost_user_set_vring_enable(struct virtio_net **pdev,
>   		enable, index);
>   
>   	vq = dev->virtqueue[index];
> -	/* vhost_user_lock_all_queue_pairs locked all qps */
> -	vq_assert_lock(dev, vq);
> -	if (enable && vq->async) {
> -		if (vq->async->pkts_inflight_n) {
> +	if (!(dev->flags & VIRTIO_DEV_VDPA_CONFIGURED)) {
> +		/* vhost_user_lock_all_queue_pairs locked all qps */
> +		vq_assert_lock(dev, vq);
> +		if (enable && vq->async && vq->async->pkts_inflight_n) {
>   			VHOST_LOG_CONFIG(dev->ifname, ERR,
>   				"failed to enable vring. Inflight packets must be completed first\n");
>   			return RTE_VHOST_MSG_RESULT_ERR;

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime