Re: [dpdk-dev] [PATCH v2] vhost: prevent disabled rings to be processed with zero-copy

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

On 2/28/19 6:57 PM, Maxime Coquelin wrote:
> The vhost-user spec says that once the vring is disabled, the
> client has to stop processing it. But it can happen when
> dequeue zero-copy is enabled if outstanding descriptors buffers
> are still being processed by an external NIC or another guest.
> 
> The fix consists in draining the zmbufs list to ensure no more
> descriptors buffers are in the wild.
> 
> Note that this fix is only working in the case REPLY_ACK
> protocol feature is enabled, which is not the case by default
> for now (it is only enabled when IOMMU feature is enabled in
> the vhost library).
> 
> Fixes: b0a985d1f340 ("vhost: add dequeue zero copy")
> Cc: stable@dpdk.org
> 
> Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>   lib/librte_vhost/vhost_user.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index 36c0c676d..555d09ad9 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -1345,6 +1345,10 @@ vhost_user_set_vring_enable(struct virtio_net **pdev,
>   		dev->notify_ops->vring_state_changed(dev->vid,
>   				index, enable);
>   
> +	/* On disable, rings have to be stopped being processed. */
> +	if (!enable && dev->dequeue_zero_copy)
> +		drain_zmbuf_list(dev->virtqueue[index]);
> +
>   	dev->virtqueue[index]->enabled = enable;
>   
>   	return RTE_VHOST_MSG_RESULT_OK;
> 

Applied to dpdk-next-virtio/master.

Maxime