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dpaa2-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: d678be1dc1 ("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>
This commit is contained in:
Magnus Karlsson 2023-01-25 08:49:01 +01:00 committed by Jakub Kicinski
parent b534013798
commit a3191c4d86
1 changed files with 6 additions and 3 deletions
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9
drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
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@ -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 @@ out:
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;