netdev - [PATCH intel-net] ixgbe: xsk: change !netif_carrier_ok() handling in ixgbe_xmit

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Date:   Thu,  3 Feb 2022 13:58:03 +0100
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     intel-wired-lan@...ts.osuosl.org
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        anthony.l.nguyen@...el.com, kuba@...nel.org, davem@...emloft.net,
        magnus.karlsson@...el.com, alexandr.lobakin@...el.com,
        jesse.brandeburg@...el.com,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Maurice Baijens <maurice.baijens@...ips.com>
Subject: [PATCH intel-net] ixgbe: xsk: change !netif_carrier_ok() handling in ixgbe_xmit_zc()

Commit c685c69fba71 ("ixgbe: don't do any AF_XDP zero-copy transmit if
netif is not OK") addressed the ring transient state when
MEM_TYPE_XSK_BUFF_POOL was being configured which in turn caused the
interface to through down/up. Maurice reported that when carrier is not
ok and xsk_pool is present on ring pair, ksoftirqd will consume 100% CPU
cycles due to the constant NAPI rescheduling as ixgbe_poll() states that
there is still some work to be done.

To fix this, do not set work_done to false for a !netif_carrier_ok().

Fixes: c685c69fba71 ("ixgbe: don't do any AF_XDP zero-copy transmit if netif is not OK")
Reported-by: Maurice Baijens <maurice.baijens@...ips.com>
Tested-by: Maurice Baijens <maurice.baijens@...ips.com>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
index b3fd8e5cd85b..6a5e9cf6b5da 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
@@ -390,12 +390,14 @@ static bool ixgbe_xmit_zc(struct ixgbe_ring *xdp_ring, unsigned int budget)
 	u32 cmd_type;
 
 	while (budget-- > 0) {
-		if (unlikely(!ixgbe_desc_unused(xdp_ring)) ||
-		    !netif_carrier_ok(xdp_ring->netdev)) {
+		if (unlikely(!ixgbe_desc_unused(xdp_ring))) {
 			work_done = false;
 			break;
 		}
 
+		if (!netif_carrier_ok(xdp_ring->netdev))
+			break;
+
 		if (!xsk_tx_peek_desc(pool, &desc))
 			break;
 
-- 
2.33.1