Re: [PATCH net v3 2/2] vhost_net: fix tx queue stuck when sendmsg fails
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: 2020-12-23 17:07:09
Also in:
virtualization
On Wed, Dec 23, 2020 at 9:47 AM wangyunjian [off-list ref] wrote:
From: Yunjian Wang <redacted> Currently the driver don't drop a packet which can't be send by tun (e.g bad packet). In this case, the driver will always process the same packet lead to the tx queue stuck. To fix this issue: 1. in the case of persistent failure (e.g bad packet), the driver can skip this descriptior by ignoring the error. 2. in the case of transient failure (e.g -EAGAIN and -ENOMEM), the driver schedules the worker to try again.
Fixes: 3a4d5c94e959 ("vhost_net: a kernel-level virtio server")
Since I have a few other comments, a few minor typo corrections too:
don't -> doesn't, send -> sent, descriptior -> descriptor.
quoted hunk ↗ jump to hunk
Signed-off-by: Yunjian Wang <redacted> drivers/vhost/net.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index c8784dfafdd7..e49dd64d086a 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c@@ -827,9 +827,8 @@ static void handle_tx_copy(struct vhost_net *net, struct socket *sock) msg.msg_flags &= ~MSG_MORE; } - /* TODO: Check specific error and bomb out unless ENOBUFS? */ err = sock->ops->sendmsg(sock, &msg, len); - if (unlikely(err < 0)) { + if (unlikely(err == -EAGAIN || err == -ENOMEM)) { vhost_discard_vq_desc(vq, 1); vhost_net_enable_vq(net, vq); break;@@ -922,7 +921,6 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock) msg.msg_flags &= ~MSG_MORE; } - /* TODO: Check specific error and bomb out unless ENOBUFS? */ err = sock->ops->sendmsg(sock, &msg, len); if (unlikely(err < 0)) { if (zcopy_used) {@@ -931,9 +929,11 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock) nvq->upend_idx = ((unsigned)nvq->upend_idx - 1) % UIO_MAXIOV; } - vhost_discard_vq_desc(vq, 1); - vhost_net_enable_vq(net, vq); - break; + if (err == -EAGAIN || err == -ENOMEM) { + vhost_discard_vq_desc(vq, 1); + vhost_net_enable_vq(net, vq); + break; + } } if (err != len) pr_debug("Truncated TX packet: "
Probably my bad for feedback in patch 2/2, but now vhost will incorrectly log bad packets as truncated packets. This will need to be if (err >= 0 && err != len). It would be nice if we could notify the guest in the transmit descriptor when a packet was dropped due to failing integrity checks (bad packet). But I don't think we easily can, so out of scope for this fix.