From: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
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 follwed 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@xxxxxxxxx>
Link: https://lore.kernel.org/r/20221220185903.1105011-1-sbohrer@xxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/20210624160609.292325-1-toke@xxxxxxxxxx/
---
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 0c35abb7d065..2e79d18fc3c7 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -1993,10 +1993,15 @@ 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();
+
/* Update NET DIM with the values for this CDAN */
dpaa2_io_update_net_dim(ch->dpio, ch->stats.frames_per_cdan,
ch->stats.bytes_per_cdan);
@@ -2032,9 +2037,7 @@ 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;
--
2.34.1
