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

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Message-Id: <20240904090853.15187-1-shivani.agarwal@broadcom.com>
Date: Wed,  4 Sep 2024 02:08:53 -0700
From: Shivani Agarwal <shivani.agarwal@...adcom.com>
To: stable@...r.kernel.org,
	gregkh@...uxfoundation.org
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,
	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>,
	Shivani Agarwal <shivani.agarwal@...adcom.com>
Subject: [PATCH v4.19-v5.10] virtio_net: Fix napi_skb_cache_put warning

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>
---
 drivers/net/virtio_net.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f7ed99561..99dea89b2 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1497,7 +1497,7 @@ static bool is_xdp_raw_buffer_queue(struct virtnet_info *vi, int q)
 		return false;
 }
 
-static void virtnet_poll_cleantx(struct receive_queue *rq)
+static void virtnet_poll_cleantx(struct receive_queue *rq, int budget)
 {
 	struct virtnet_info *vi = rq->vq->vdev->priv;
 	unsigned int index = vq2rxq(rq->vq);
@@ -1508,7 +1508,7 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
 		return;
 
 	if (__netif_tx_trylock(txq)) {
-		free_old_xmit_skbs(sq, true);
+		free_old_xmit_skbs(sq, !!budget);
 		__netif_tx_unlock(txq);
 	}
 
@@ -1525,7 +1525,7 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
 	unsigned int received;
 	unsigned int xdp_xmit = 0;
 
-	virtnet_poll_cleantx(rq);
+	virtnet_poll_cleantx(rq, budget);
 
 	received = virtnet_receive(rq, budget, &xdp_xmit);
 
@@ -1598,7 +1598,7 @@ static int virtnet_poll_tx(struct napi_struct *napi, int budget)
 	txq = netdev_get_tx_queue(vi->dev, index);
 	__netif_tx_lock(txq, raw_smp_processor_id());
 	virtqueue_disable_cb(sq->vq);
-	free_old_xmit_skbs(sq, true);
+	free_old_xmit_skbs(sq, !!budget);
 
 	opaque = virtqueue_enable_cb_prepare(sq->vq);
 
-- 
2.39.4