From: Magnus Karlsson magnus.karlsson@intel.com
[ Upstream commit a3191c4d86c5d3bd35b00dfde6910b88391436a0 ]
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: d678be1dc1ec ("dpaa2-eth: add XDP_REDIRECT support") 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/ Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c index 5899139aec97..c48d41093651 100644 --- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c +++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c @@ -1597,10 +1597,15 @@ static int dpaa2_eth_poll(struct napi_struct *napi, int budget) if (rx_cleaned >= budget || txconf_cleaned >= DPAA2_ETH_TXCONF_PER_NAPI) { work_done = budget; + if (ch->xdp.res & XDP_REDIRECT) + xdp_do_flush(); goto out; } } while (store_cleaned);
+ if (ch->xdp.res & XDP_REDIRECT) + xdp_do_flush(); + /* We didn't consume the entire budget, so finish napi and * re-enable data availability notifications */ @@ -1625,9 +1630,7 @@ static int dpaa2_eth_poll(struct napi_struct *napi, int budget) txc_fq->dq_bytes = 0; }
- if (ch->xdp.res & XDP_REDIRECT) - xdp_do_flush_map(); - else if (rx_cleaned && ch->xdp.res & XDP_TX) + if (rx_cleaned && ch->xdp.res & XDP_TX) dpaa2_eth_xdp_tx_flush(priv, ch, &priv->fq[flowid]);
return work_done;