linux-kernel - Re: [PATCH v4.19-v5.10] virtio_net: Fix napi_skb_cache

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Message-ID: <2024090539-refusing-contour-2dbc@gregkh>
Date: Thu, 5 Sep 2024 10:00:47 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Shivani Agarwal <shivani.agarwal@...adcom.com>
Cc: stable@...r.kernel.org, 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, virtualization@...ts.linux.dev,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	ajay.kaher@...adcom.com, alexey.makhalov@...adcom.com,
	vasavi.sirnapalli@...adcom.com, Breno Leitao <leitao@...ian.org>,
	Heng Qi <hengqi@...ux.alibaba.com>, Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH v4.19-v5.10] virtio_net: Fix napi_skb_cache_put warning

On Wed, Sep 04, 2024 at 02:08:53AM -0700, Shivani Agarwal wrote:
> From: Breno Leitao <leitao@...ian.org>
> 
> [ Upstream commit f8321fa75102246d7415a6af441872f6637c93ab ]
> 
> 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@...nel.org>
> Signed-off-by: Breno Leitao <leitao@...ian.org>
> Reviewed-by: Jakub Kicinski <kuba@...nel.org>
> Acked-by: Michael S. Tsirkin <mst@...hat.com>
> Acked-by: Jason Wang <jasowang@...hat.com>
> Reviewed-by: Heng Qi <hengqi@...ux.alibaba.com>
> Link: https://patch.msgid.link/20240712115325.54175-1-leitao@debian.org
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> [Shivani: Modified to apply on v4.19.y-v5.10.y]
> Signed-off-by: Shivani Agarwal <shivani.agarwal@...adcom.com>

All now queued up, thanks.

greg k-h