> -----Original Message-----
> From: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
> Sent: Wednesday, January 25, 2023 9:49
> To: magnus.karlsson@xxxxxxxxx; bjorn@xxxxxxxxxx; ast@xxxxxxxxxx;
> daniel@xxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx;
> jonathan.lemon@xxxxxxxxx; maciej.fijalkowski@xxxxxxxxx;
> kuba@xxxxxxxxxx; toke@xxxxxxxxxx; pabeni@xxxxxxxxxx;
> davem@xxxxxxxxxxxxx; aelior@xxxxxxxxxxx; manishc@xxxxxxxxxxx;
> horatiu.vultur@xxxxxxxxxxxxx; UNGLinuxDriver@xxxxxxxxxxxxx;
> mst@xxxxxxxxxx; jasowang@xxxxxxxxxx; Ioana Ciornei
> <ioana.ciornei@xxxxxxx>; Madalin Bucur <madalin.bucur@xxxxxxx>
> Cc: bpf@xxxxxxxxxxxxxxx
> Subject: [PATCH net v2 4/5] dpaa_eth: execute xdp_do_flush() before
> napi_complete_done()
>
> 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: 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>
Thanks!
> drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> index 3f8032947d86..027fff9f7db0 100644
> --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> @@ -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;
> }
>
> --
> 2.34.1
