Patch "qede: execute xdp_do_flush() before napi_complete_done()" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    qede: execute xdp_do_flush() before napi_complete_done()

to the 5.15-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:
     qede-execute-xdp_do_flush-before-napi_complete_done.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit c17b511864ff2e0f322ad13d6ebef96ceca35b07
Author: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
Date:   Wed Jan 25 08:48:57 2023 +0100

    qede: execute xdp_do_flush() before napi_complete_done()
    
    [ Upstream commit 2ccce20d51faa0178086163ccb6c84a099a87ab4 ]
    
    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/
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/ethernet/qlogic/qede/qede_fp.c b/drivers/net/ethernet/qlogic/qede/qede_fp.c
index 17f895250e04..d67d4e74b326 100644
--- a/drivers/net/ethernet/qlogic/qede/qede_fp.c
+++ b/drivers/net/ethernet/qlogic/qede/qede_fp.c
@@ -1439,6 +1439,10 @@ 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)) {
@@ -1458,9 +1462,6 @@ 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;
 }