RE: [PATCH] igc: Fix trigger of incorrect irq in igc_xsk_wakeup function
From: Behera, VIVEK <hidden>
Date: 2025-12-09 06:03:13
Also in:
intel-wired-lan, lkml
Hi Jacob, Thank you very much for taking the time to review the patch and for the `Reviewed-by:` tag! I really appreciate your feedback. Just wanted to let you know that I had already sent out `v2` of this patch, which included the PTP TX wakeup fix and addressed some `checkpatch.pl` comments. For `v3`, I will incorporate your suggestions and send it out shortly. Thanks again, Vivek Behera -----Original Message----- From: Jacob Keller <jacob.e.keller@intel.com> Sent: Tuesday, December 9, 2025 12:54 AM To: Behera, Vivek (DI FA DSP ICC PRC1) <redacted>; Tony Nguyen <anthony.l.nguyen@intel.com>; Przemek Kitszel <przemyslaw.kitszel@intel.com>; Andrew Lunn <andrew+netdev@lunn.ch>; David S. Miller <davem@davemloft.net>; Eric Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com> Cc: intel-wired-lan@lists.osuosl.org; netdev@vger.kernel.org; linux-kernel@vger.kernel.org Subject: Re: [PATCH] igc: Fix trigger of incorrect irq in igc_xsk_wakeup function On 12/5/2025 4:39 AM, Behera, VIVEK wrote:
From 4e3ebdc0af6baa83ccfc17c61c1eb61408095ffd Mon Sep 17 00:00:00 2001 From: Vivek Behera <redacted> Date: Fri, 5 Dec 2025 10:26:05 +0100 Subject: [PATCH] igc: Fix trigger of incorrect irq in igc_xsk_wakeup function When the i226 is configured to use only 2 combined queues using ethtool or in an environment with only 2 active CPU cores the 4 irq lines are used in a split configuration with one irq assigned to each of the two rx and tx queues (see console output below) sudo ethtool -l enp1s0 Channel parameters for enp1s0: Pre-set maximums: RX: n/a TX: n/a Other: 1 Combined: 4 Current hardware settings: RX: n/a TX: n/a Other: 1 Combined: 2 eddx@mvs:~$ cat /proc/interrupts | grep enp1s0 147: 1 0 IR-PCI-MSIX-0000:01:00.0 0-edge enp1s0 148: 8 0 IR-PCI-MSIX-0000:01:00.0 1-edge enp1s0-rx-0 149: 0 0 IR-PCI-MSIX-0000:01:00.0 2-edge enp1s0-rx-1 150: 26 0 IR-PCI-MSIX-0000:01:00.0 3-edge enp1s0-tx-0 151: 0 0 IR-PCI-MSIX-0000:01:00.0 4-edge enp1s0-tx-1 While testing with the RTC Testbench it was noticed using the bpftrace that the igc_xsk_wakeup when triggered by xsk_sendmsg was triggering the incorrect irq for tx-0(see trace below) TIMESTAMP: 456992309829 | FUNCTION: igc_xsk_wakeup | ENTRY: RtcTxThread (PID: 945) - queue_id: 0 TIMESTAMP: 456992317157 | FUNCTION: igc_poll | ENTRY: irq/148-enp1s0- (PID: 948) TIMESTAMP: 456993309408 | FUNCTION: igc_xsk_wakeup | ENTRY: RtcTxThread (PID: 945) - queue_id: 0 TIMESTAMP: 456993316591 | FUNCTION: igc_poll | ENTRY: irq/148-enp1s0- (PID: 948) TIMESTAMP: 456994309630 | FUNCTION: igc_xsk_wakeup | ENTRY: RtcTxThread (PID: 945) - queue_id: 0 TIMESTAMP: 456994316674 | FUNCTION: igc_poll | ENTRY: irq/148-enp1s0- (PID: 948) TIMESTAMP: 456995309493 | FUNCTION: igc_xsk_wakeup | ENTRY: RtcTxThread (PID: 945) - queue_id: 0 TIMESTAMP: 456995316593 | FUNCTION: igc_poll | ENTRY: irq/148-enp1s0- (PID: 948) Due to this bug no XDP Zc send is possible in this split irq configuration. This patch implements the correct logic of extracting the q_vectors saved duirng the rx and tx ring allocation. Furthermore the patch includes usage of flags provided by the ndo_xsk_wakeup api to trigger the required irq. With this patch correct irqs are triggered cat /proc/interrupts | grep enp1s0 161: 1 0 0 0 IR-PCI-MSIX-0000:01:00.0 0-edge enp1s0 162: 2 0 0 0 IR-PCI-MSIX-0000:01:00.0 1-edge enp1s0-rx-0 163: 359 0 0 0 IR-PCI-MSIX-0000:01:00.0 2-edge enp1s0-rx-1 164: 872005 0 0 0 IR-PCI-MSIX-0000:01:00.0 3-edge enp1s0-tx-0 165: 71 0 0 0 IR-PCI-MSIX-0000:01:00.0 4-edge enp1s0-tx-1 TIMESTAMP: 149658589239205 | FUNCTION: igc_xsk_wakeup | ENTRY: RtcTxThread (PID: 10633) - queue_id: 0 TIMESTAMP: 149658589244662 | FUNCTION: igc_poll | ENTRY: irq/164-enp1s0- (PID: 10593) TIMESTAMP: 149658589293396 | FUNCTION: igc_poll | ENTRY: irq/164-enp1s0- (PID: 10593) TIMESTAMP: 149658589295357 | FUNCTION: xsk_tx_completed | ENTRY: irq/164-enp1s0- (PID: 10593) - num_entries: 61 TIMESTAMP: 149658589342151 | FUNCTION: igc_poll | ENTRY: irq/164-enp1s0- (PID: 10593) TIMESTAMP: 149658589343881 | FUNCTION: xsk_tx_completed | ENTRY: irq/164-enp1s0- (PID: 10593) - num_entries: 3 TIMESTAMP: 149658589391394 | FUNCTION: igc_poll | ENTRY: irq/164-enp1s0- (PID: 10593) TIMESTAMP: 149658590239215 | FUNCTION: igc_xsk_wakeup | ENTRY: RtcTxThread (PID: 10633) - queue_id: 0
I appreciate the detailed outline of how to configure the system so this fails, and the steps taken to verify the change fixes the issue.
Signed-off-by: Vivek Behera <redacted>
This is a bug fix, so it should be targeted at net. You will need a Fixes tag associating which commit this fixes as well. Alternatively, since this is for an Intel networking driver and you sent it to Intel Wired LAN, it would be "iwl-net" so that it gets picked up by Tony for testing along with our other igc changes.
quoted hunk ↗ jump to hunk
--- drivers/net/ethernet/intel/igc/igc_main.c | 31 +++++++++++++++++++---- 1 file changed, 26 insertions(+), 5 deletions(-)diff --git a/drivers/net/ethernet/intel/igc/igc_main.cb/drivers/net/ethernet/intel/igc/igc_main.c index 7aafa60ba0c8..0cfcd20a2536 100644--- a/drivers/net/ethernet/intel/igc/igc_main.c +++ b/drivers/net/ethernet/intel/igc/igc_main.c@@ -6930,21 +6930,42 @@ int igc_xsk_wakeup(struct net_device *dev, u32 queue_id, u32 flags) if (!igc_xdp_is_enabled(adapter)) return -ENXIO; - if (queue_id >= adapter->num_rx_queues) + if ((flags & XDP_WAKEUP_RX) && (flags & XDP_WAKEUP_TX)) { + /* If both TX and RX need to be woken up queue pair per IRQ is needed */ + if (!(adapter->flags & IGC_FLAG_QUEUE_PAIRS)) + return -EINVAL; /* igc queue pairs are not activated. + * Can't trigger irq + */
We only have to check for queue pairs if we want to wake both. Makes sense.
+ /* Just get the ring params from Rx */
+ if (queue_id >= adapter->num_rx_queues)
+ return -EINVAL;
+ ring = adapter->rx_ring[queue_id];
+ } else if (flags & XDP_WAKEUP_TX) {
+ if (queue_id >= adapter->num_tx_queues)
+ return -EINVAL;
+ /* Get the ring params from Tx */
+ ring = adapter->tx_ring[queue_id];
+ } else if (flags & XDP_WAKEUP_RX) {
+ if (queue_id >= adapter->num_rx_queues)
+ return -EINVAL;
+ /* Get the ring params from Rx */
+ ring = adapter->rx_ring[queue_id];
+ } else {
+ /* Invalid Flags */
return -EINVAL;
-
- ring = adapter->rx_ring[queue_id];
+ }
if (!ring->xsk_pool)
return -ENXIO;
-
- q_vector = adapter->q_vector[queue_id];
+ /* Retrieve the q_vector saved in the ring */
+ q_vector = ring->q_vector;
if (!napi_if_scheduled_mark_missed(&q_vector->napi))
igc_trigger_rxtxq_interrupt(adapter, q_vector);The actual code changes seem correct to me, so you may add my review tag on a version which has the Fixes and the appropriate tree tag i.e. [iwl-net] or [PATCH iwl-net]. Reviewed-by: Jacob Keller <redacted> Thanks, Jake