This is a note to let you know that I've just added the patch titled
dpaa_eth: execute xdp_do_flush() before napi_complete_done()
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dpaa_eth-execute-xdp_do_flush-before-napi_complete_d.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 887859ffa95dbcb485c7c66c3bbfab2c2c8862b2
Author: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
Date: Wed Jan 25 08:49:00 2023 +0100
dpaa_eth: execute xdp_do_flush() before napi_complete_done()
[ Upstream commit b534013798b77f81a36f36dafd59bab9de837619 ]
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: a1e031ffb422 ("dpaa_eth: add XDP_REDIRECT support")
Signed-off-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
Acked-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221220185903.1105011-1-sbohrer@xxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/20210624160609.292325-1-toke@xxxxxxxxxx/
Acked-by: Camelia Groza <camelia.groza@xxxxxxx>
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index fc68a32ce2f7..d8fb7d4ebd51 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
@@ -2400,6 +2400,9 @@ static int dpaa_eth_poll(struct napi_struct *napi, int budget)
cleaned = qman_p_poll_dqrr(np->p, budget);
+ if (np->xdp_act & XDP_REDIRECT)
+ xdp_do_flush();
+
if (cleaned < budget) {
napi_complete_done(napi, cleaned);
qman_p_irqsource_add(np->p, QM_PIRQ_DQRI);
@@ -2407,9 +2410,6 @@ static int dpaa_eth_poll(struct napi_struct *napi, int budget)
qman_p_irqsource_add(np->p, QM_PIRQ_DQRI);
}
- if (np->xdp_act & XDP_REDIRECT)
- xdp_do_flush();
-
return cleaned;
}
