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authorMagnus Karlsson <magnus.karlsson@intel.com>2023-01-25 10:48:59 +0300
committerJakub Kicinski <kuba@kernel.org>2023-01-28 09:27:59 +0300
commitad7e615f646c9b5b2cf655cdfb9d91a28db4f25a (patch)
treed82367374b50b302581fb509fa1e4ff554e742f0 /drivers/net/virtio_net.c
parent12b5717990c81fc2f6f2aa9d53d960b916478d4f (diff)
downloadlinux-ad7e615f646c9b5b2cf655cdfb9d91a28db4f25a.tar.xz
virtio-net: execute xdp_do_flush() before napi_complete_done()
Make sure that xdp_do_flush() is always executed before napi_complete_done(). This is important for two reasons. First, a redirect to an XSKMAP assumes that a call to xdp_do_redirect() from napi context X on CPU Y will be followed by a xdp_do_flush() from the same napi context and CPU. This is not guaranteed if the napi_complete_done() is executed before xdp_do_flush(), as it tells the napi logic that it is fine to schedule napi context X on another CPU. Details from a production system triggering this bug using the veth driver can be found following the first link below. The second reason is that the XDP_REDIRECT logic in itself relies on being inside a single NAPI instance through to the xdp_do_flush() call for RCU protection of all in-kernel data structures. Details can be found in the second link below. Fixes: 186b3c998c50 ("virtio-net: support XDP_REDIRECT") Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com> Acked-by: Toke Høiland-Jørgensen <toke@redhat.com> Link: https://lore.kernel.org/r/20221220185903.1105011-1-sbohrer@cloudflare.com Link: https://lore.kernel.org/all/20210624160609.292325-1-toke@redhat.com/ Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'drivers/net/virtio_net.c')
-rw-r--r--drivers/net/virtio_net.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 18b3de854aeb..6df14dd5bf46 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1677,13 +1677,13 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
received = virtnet_receive(rq, budget, &xdp_xmit);
+ if (xdp_xmit & VIRTIO_XDP_REDIR)
+ xdp_do_flush();
+
/* Out of packets? */
if (received < budget)
virtqueue_napi_complete(napi, rq->vq, received);
- if (xdp_xmit & VIRTIO_XDP_REDIR)
- xdp_do_flush();
-
if (xdp_xmit & VIRTIO_XDP_TX) {
sq = virtnet_xdp_get_sq(vi);
if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq)) {