From: Jason Wang Date: Tue, 5 Sep 2017 01:22:05 +0000 (+0800) Subject: vhost_net: correctly check tx avail during rx busy polling X-Git-Tag: Ubuntu-4.13.0-12.13~73 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=4ab0b8d31d3f507d46e042e9094d06274c1c30a4;p=mirror_ubuntu-artful-kernel.git vhost_net: correctly check tx avail during rx busy polling BugLink: http://bugs.launchpad.net/bugs/1718412 [ Upstream commit 8b949bef9172ca69d918e93509a4ecb03d0355e0 ] We check tx avail through vhost_enable_notify() in the past which is wrong since it only checks whether or not guest has filled more available buffer since last avail idx synchronization which was just done by vhost_vq_avail_empty() before. What we really want is checking pending buffers in the avail ring. Fix this by calling vhost_vq_avail_empty() instead. This issue could be noticed by doing netperf TCP_RR benchmark as client from guest (but not host). With this fix, TCP_RR from guest to localhost restores from 1375.91 trans per sec to 55235.28 trans per sec on my laptop (Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz). Fixes: 030881372460 ("vhost_net: basic polling support") Signed-off-by: Jason Wang Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Seth Forshee --- diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 06d044862e58..1c75572f5a3f 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -634,8 +634,13 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk) preempt_enable(); - if (vhost_enable_notify(&net->dev, vq)) + if (!vhost_vq_avail_empty(&net->dev, vq)) vhost_poll_queue(&vq->poll); + else if (unlikely(vhost_enable_notify(&net->dev, vq))) { + vhost_disable_notify(&net->dev, vq); + vhost_poll_queue(&vq->poll); + } + mutex_unlock(&vq->mutex); len = peek_head_len(rvq, sk);