Re: [PATCH net-next] virtio_net: Fix napi_skb_cache_put warning

[Jakub Kicinski]

On Fri, 12 Jul 2024 04:53:25 -0700 Breno Leitao wrote:
> After the commit bdacf3e34945 ("net: Use nested-BH locking for
> napi_alloc_cache.") was merged, the following warning began to appear:
> 
> 	 WARNING: CPU: 5 PID: 1 at net/core/skbuff.c:1451 napi_skb_cache_put+0x82/0x4b0
> 
> 	  __warn+0x12f/0x340
> 	  napi_skb_cache_put+0x82/0x4b0
> 	  napi_skb_cache_put+0x82/0x4b0
> 	  report_bug+0x165/0x370
> 	  handle_bug+0x3d/0x80
> 	  exc_invalid_op+0x1a/0x50
> 	  asm_exc_invalid_op+0x1a/0x20
> 	  __free_old_xmit+0x1c8/0x510
> 	  napi_skb_cache_put+0x82/0x4b0
> 	  __free_old_xmit+0x1c8/0x510
> 	  __free_old_xmit+0x1c8/0x510
> 	  __pfx___free_old_xmit+0x10/0x10
> 
> The issue arises because virtio is assuming it's running in NAPI context
> even when it's not, such as in the netpoll case.
> 
> To resolve this, modify virtnet_poll_tx() to only set NAPI when budget
> is available. Same for virtnet_poll_cleantx(), which always assumed that
> it was in a NAPI context.
> 
> Fixes: df133f3f9625 ("virtio_net: bulk free tx skbs")
> Suggested-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>

Reviewed-by: Jakub Kicinski <kuba@xxxxxxxxxx>