diff options
| author | Magnus Karlsson <magnus.karlsson@intel.com> | 2023-01-25 10:48:59 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2023-01-28 09:27:59 +0300 |
| commit | ad7e615f646c9b5b2cf655cdfb9d91a28db4f25a (patch) | |
| tree | d82367374b50b302581fb509fa1e4ff554e742f0 | |
| parent | 12b5717990c81fc2f6f2aa9d53d960b916478d4f (diff) | |
| download | linux-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>
| -rw-r--r-- | drivers/net/virtio_net.c | 6 |
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)) { |