netdev - [PATCH net] virtio_net: move netdev_tx_reset

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Message-ID: <20240814122500.1710279-1-jiri@resnulli.us>
Date: Wed, 14 Aug 2024 14:25:00 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: virtualization@...ts.linux.dev
Cc: mst@...hat.com,
	jasowang@...hat.com,
	xuanzhuo@...ux.alibaba.com,
	eperezma@...hat.com,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	netdev@...r.kernel.org,
	m.szyprowski@...sung.com
Subject: [PATCH net] virtio_net: move netdev_tx_reset_queue() call before RX napi enable

From: Jiri Pirko <jiri@...dia.com>

During suspend/resume the following BUG was hit:
------------[ cut here ]------------
kernel BUG at lib/dynamic_queue_limits.c:99!
Internal error: Oops - BUG: 0 [#1] SMP ARM
Modules linked in: bluetooth ecdh_generic ecc libaes
CPU: 1 PID: 1282 Comm: rtcwake Not tainted
6.10.0-rc3-00732-gc8bd1f7f3e61 #15240
Hardware name: Generic DT based system
PC is at dql_completed+0x270/0x2cc
LR is at __free_old_xmit+0x120/0x198
pc : [<c07ffa54>]    lr : [<c0c42bf4>]    psr: 80000013
...
Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 10c5387d  Table: 43a4406a  DAC: 00000051
...
Process rtcwake (pid: 1282, stack limit = 0xfbc21278)
Stack: (0xe0805e80 to 0xe0806000)
...
Call trace:
  dql_completed from __free_old_xmit+0x120/0x198
  __free_old_xmit from free_old_xmit+0x44/0xe4
  free_old_xmit from virtnet_poll_tx+0x88/0x1b4
  virtnet_poll_tx from __napi_poll+0x2c/0x1d4
  __napi_poll from net_rx_action+0x140/0x2b4
  net_rx_action from handle_softirqs+0x11c/0x350
  handle_softirqs from call_with_stack+0x18/0x20
  call_with_stack from do_softirq+0x48/0x50
  do_softirq from __local_bh_enable_ip+0xa0/0xa4
  __local_bh_enable_ip from virtnet_open+0xd4/0x21c
  virtnet_open from virtnet_restore+0x94/0x120
  virtnet_restore from virtio_device_restore+0x110/0x1f4
  virtio_device_restore from dpm_run_callback+0x3c/0x100
  dpm_run_callback from device_resume+0x12c/0x2a8
  device_resume from dpm_resume+0x12c/0x1e0
  dpm_resume from dpm_resume_end+0xc/0x18
  dpm_resume_end from suspend_devices_and_enter+0x1f0/0x72c
  suspend_devices_and_enter from pm_suspend+0x270/0x2a0
  pm_suspend from state_store+0x68/0xc8
  state_store from kernfs_fop_write_iter+0x10c/0x1cc
  kernfs_fop_write_iter from vfs_write+0x2b0/0x3dc
  vfs_write from ksys_write+0x5c/0xd4
  ksys_write from ret_fast_syscall+0x0/0x54
Exception stack(0xe8bf1fa8 to 0xe8bf1ff0)
...
---[ end trace 0000000000000000 ]---

After virtnet_napi_enable() is called, the following path is hit:
  __napi_poll()
    -> virtnet_poll()
      -> virtnet_poll_cleantx()
        -> netif_tx_wake_queue()

That wakes the TX queue and allows skbs to be submitted and accounted by
BQL counters.

Then netdev_tx_reset_queue() is called that resets BQL counters and
eventually leads to the BUG in dql_completed().

Move virtnet_napi_tx_enable() what does BQL counters reset before RX
napi enable to avoid the issue.

Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Closes: https://lore.kernel.org/netdev/e632e378-d019-4de7-8f13-07c572ab37a9@samsung.com/
Fixes: c8bd1f7f3e61 ("virtio_net: add support for Byte Queue Limits")
Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
Signed-off-by: Jiri Pirko <jiri@...dia.com>
---
 drivers/net/virtio_net.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 3f10c72743e9..c6af18948092 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2867,8 +2867,8 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
 	if (err < 0)
 		goto err_xdp_reg_mem_model;
 
-	virtnet_napi_enable(vi->rq[qp_index].vq, &vi->rq[qp_index].napi);
 	netdev_tx_reset_queue(netdev_get_tx_queue(vi->dev, qp_index));
+	virtnet_napi_enable(vi->rq[qp_index].vq, &vi->rq[qp_index].napi);
 	virtnet_napi_tx_enable(vi, vi->sq[qp_index].vq, &vi->sq[qp_index].napi);
 
 	return 0;
-- 
2.45.2