netdev - Re: [PATCH net-next] virtio_net: Fix napi_skb_cache

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Message-ID: <CACGkMEtDDCtF3FrjOppS=+Fmb1uHZborXn3biuRKV4iTwHmVaw@mail.gmail.com>
Date: Mon, 15 Jul 2024 09:08:28 +0800
From: Jason Wang <jasowang@...hat.com>
To: Breno Leitao <leitao@...ian.org>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
	Eugenio Pérez <eperezma@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, rbc@...a.com, horms@...nel.org, 
	"open list:VIRTIO CORE AND NET DRIVERS" <virtualization@...ts.linux.dev>, 
	"open list:NETWORKING DRIVERS" <netdev@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next] virtio_net: Fix napi_skb_cache_put warning

On Fri, Jul 12, 2024 at 7:54 PM Breno Leitao <leitao@...ian.org> 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@...nel.org>
> Signed-off-by: Breno Leitao <leitao@...ian.org>
> ---

Acked-by: Jason Wang <jasowang@...hat.com>

Thanks