netdev - [PATCH net-next V2 2/3] vhost_net: support in order feature

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Date:   Wed,  9 Jan 2019 16:05:29 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     mst@...hat.com, jasowang@...hat.com
Cc:     kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-next V2 2/3] vhost_net: support in order feature

This makes vhost_net to support in order feature. This is as simple as
use datacopy path when it was negotiated. An alternative is not to
advertise in order when zerocopy is enabled which tends to be
suboptimal consider zerocopy may suffer from e.g HOL issues.

Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 drivers/vhost/net.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 36f3d0f49e60..0870f51a1c76 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -74,7 +74,8 @@ enum {
 	VHOST_NET_FEATURES = VHOST_FEATURES |
 			 (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
 			 (1ULL << VIRTIO_NET_F_MRG_RXBUF) |
-			 (1ULL << VIRTIO_F_IOMMU_PLATFORM)
+			 (1ULL << VIRTIO_F_IOMMU_PLATFORM) |
+	                 (1ULL << VIRTIO_F_IN_ORDER)
 };
 
 enum {
@@ -977,7 +978,8 @@ static void handle_tx(struct vhost_net *net)
 	vhost_disable_notify(&net->dev, vq);
 	vhost_net_disable_vq(net, vq);
 
-	if (vhost_sock_zcopy(sock))
+	if (vhost_sock_zcopy(sock) &&
+	    !vhost_has_feature(vq, VIRTIO_F_IN_ORDER))
 		handle_tx_zerocopy(net, sock);
 	else
 		handle_tx_copy(net, sock);
-- 
2.17.1