netdev - [PATCH v6.6] virtio_net: Fix napi_skb_cache

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Message-Id: <20240904085829.14684-1-shivani.agarwal@broadcom.com>
Date: Wed,  4 Sep 2024 01:58:29 -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 v6.6] 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 v6.6.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 51ade909c84f..bc01f2dafa94 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2140,7 +2140,7 @@ static int virtnet_receive(struct receive_queue *rq, int budget,
 	return packets;
 }
 
-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);
@@ -2158,7 +2158,7 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
 
 		do {
 			virtqueue_disable_cb(sq->vq);
-			free_old_xmit_skbs(sq, true);
+			free_old_xmit_skbs(sq, !!budget);
 		} while (unlikely(!virtqueue_enable_cb_delayed(sq->vq)));
 
 		if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
@@ -2177,7 +2177,7 @@ 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);
 
@@ -2280,7 +2280,7 @@ 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);
 
 	if (sq->vq->num_free >= 2 + MAX_SKB_FRAGS)
 		netif_tx_wake_queue(txq);
-- 
2.39.4