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 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: d1b25b79e162b ("qede: add .ndo_xdp_xmit() and 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/
---
drivers/net/ethernet/qlogic/qede/qede_fp.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/qlogic/qede/qede_fp.c b/drivers/net/ethernet/qlogic/qede/qede_fp.c
index 7c2af482192d..cb1746bc0e0c 100644
--- a/drivers/net/ethernet/qlogic/qede/qede_fp.c
+++ b/drivers/net/ethernet/qlogic/qede/qede_fp.c
@@ -1438,6 +1438,10 @@ int qede_poll(struct napi_struct *napi, int budget)
rx_work_done = (likely(fp->type & QEDE_FASTPATH_RX) &&
qede_has_rx_work(fp->rxq)) ?
qede_rx_int(fp, budget) : 0;
+
+ if (fp->xdp_xmit & QEDE_XDP_REDIRECT)
+ xdp_do_flush();
+
/* Handle case where we are called by netpoll with a budget of 0 */
if (rx_work_done < budget || !budget) {
if (!qede_poll_is_more_work(fp)) {
@@ -1457,9 +1461,6 @@ int qede_poll(struct napi_struct *napi, int budget)
qede_update_tx_producer(fp->xdp_tx);
}
- if (fp->xdp_xmit & QEDE_XDP_REDIRECT)
- xdp_do_flush_map();
-
return rx_work_done;
}
--
2.34.1
