From eed913f6919e253f35d454b2f115f2a4db2b741a Mon Sep 17 00:00:00 2001

From: Akihiko Odaki <akihiko.odaki@daynix.com>

Date: Fri, 28 Oct 2022 22:00:00 +0900

Subject: [PATCH] e1000e: Fix TX dispatch condition

Git-commit: eed913f6919e253f35d454b2f115f2a4db2b741a

Patch-mainline: v6.1

References: git-fixes

e1000_xmit_frame is expected to stop the queue and dispatch frames to

hardware if there is not sufficient space for the next frame in the

buffer, but sometimes it failed to do so because the estimated maximum

size of frame was wrong. As the consequence, the later invocation of

e1000_xmit_frame failed with NETDEV_TX_BUSY, and the frame in the buffer

remained forever, resulting in a watchdog failure.

This change fixes the estimated size by making it match with the

condition for NETDEV_TX_BUSY. Apparently, the old estimation failed to

account for the following lines which determines the space requirement

for not causing NETDEV_TX_BUSY:

    ```

    	/* reserve a descriptor for the offload context */

    	if ((mss) || (skb->ip_summed == CHECKSUM_PARTIAL))

    		count++;

    	count++;

    	count += DIV_ROUND_UP(len, adapter->tx_fifo_limit);

    ```

This issue was found when running http-stress02 test included in Linux

Test Project 20220930 on QEMU with the following commandline:

```

qemu-system-x86_64 -M q35,accel=kvm -m 8G -smp 8

	-drive if=virtio,format=raw,file=root.img,file.locking=on

	-device e1000e,netdev=netdev

	-netdev tap,script=ifup,downscript=no,id=netdev

```

Fixes: bc7f75fa9788 ("[E1000E]: New pci-express e1000 driver (currently for ICH9 devices only)")

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>

Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)

Tested-by: Naama Meir <naamax.meir@linux.intel.com>

Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 drivers/net/ethernet/intel/e1000e/netdev.c | 4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c

index 49e926959ad3..55cf2f62bb30 100644

--- a/drivers/net/ethernet/intel/e1000e/netdev.c

+++ b/drivers/net/ethernet/intel/e1000e/netdev.c

@@ -5936,9 +5936,9 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb,

 		e1000_tx_queue(tx_ring, tx_flags, count);

 		/* Make sure there is space in the ring for the next send. */

 		e1000_maybe_stop_tx(tx_ring,

-				    (MAX_SKB_FRAGS *

+				    ((MAX_SKB_FRAGS + 1) *

 				     DIV_ROUND_UP(PAGE_SIZE,

-						  adapter->tx_fifo_limit) + 2));

+						  adapter->tx_fifo_limit) + 4));

 		if (!netdev_xmit_more() ||

 		    netif_xmit_stopped(netdev_get_tx_queue(netdev, 0))) {

-- 

2.35.3