[dpdk-stable] [PATCH 19.11] vhost: remove zero-copy and client mode restriction

[Kevin Traynor <ktraynor@redhat.com>]

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 a6ae060e3995
("vhost: prevent zero-copy with incompatible client mode")

commit 1c2eaf9a9852
("vhost: fix zero-copy server mode")

Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
---
Cc: xuan.ding@intel.com
Cc: bluca@debian.org
---
 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 2461549fea..dc3ee1e99d 100644
--- a/lib/librte_vhost/socket.c
+++ b/lib/librte_vhost/socket.c
@@ -927,10 +927,8 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
 			goto out_mutex;
 		}
-		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);
-- 
2.21.3