Re: [dpdk-stable] [PATCH 18.11] vhost: remove zero-copy and client mode restriction

[Luca Boccassi <bluca@debian.org>]

On Wed, 2020-07-01 at 14:52 +0100, Kevin Traynor wrote:
> Commits [1] were backported as fixes from the latest DPDK release
> to the stable branches. They are detecting if vhost-user client and
> zero-copy are being used together. As this can be problematic in
> some cases, this combination was being rejected by those patches.
> 
> It might be ok to deprecate this combination in latest DPDK,
> but for stable releases we should not remove the functionality
> as it may be in use with earlier releases from the same stable branch.
> 
> In fact, we know that this functionality is used at least in OVS in
> multiple releases/active branches.
> 
> This patch removes the restriction of zero-copy and client mode
> and adds a warning for the user.
> 
> [1]
> commit 81e025d7ed6a
> ("vhost: prevent zero-copy with incompatible client mode")
> 
> commit 0309429b1988
> ("vhost: fix zero-copy server mode")
> 
> Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
> ---
> Cc: xuan.ding@intel.com
> ---
>  lib/librte_vhost/socket.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
> index 4819d31737..6f7142be23 100644
> --- a/lib/librte_vhost/socket.c
> +++ b/lib/librte_vhost/socket.c
> @@ -891,10 +891,8 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
>  	 */
>  	if (vsocket->dequeue_zero_copy) {
> -		if ((flags & RTE_VHOST_USER_CLIENT) != 0) {
> -			RTE_LOG(ERR, VHOST_CONFIG,
> -			"error: zero copy is incompatible with vhost client mode\n");
> -			ret = -1;
> -			goto out_mutex;
> -		}
> +		if ((flags & RTE_VHOST_USER_CLIENT) != 0)
> +			RTE_LOG(WARNING, VHOST_CONFIG,
> +			"zero copy may be incompatible with vhost client mode\n");
> +
>  		vsocket->supported_features &= ~(1ULL << VIRTIO_F_IN_ORDER);
>  		vsocket->features &= ~(1ULL << VIRTIO_F_IN_ORDER);

Acked-by: Luca Boccassi <bluca@debian.org>

-- 
Kind regards,
Luca Boccassi