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dpaa_eth: execute xdp_do_flush() before napi_complete_done()

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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: a1e031ffb4 ("dpaa_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/
Acked-by: Camelia Groza <camelia.groza@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Magnus Karlsson 2023-01-25 08:49:00 +01:00 committed by Jakub Kicinski
parent ad7e615f64
commit b534013798
1 changed files with 3 additions and 3 deletions
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6
drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
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@ -2410,6 +2410,9 @@ 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);
@ -2417,9 +2420,6 @@ 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;
}