6.12-stable review patch. If anyone has any objections, please let me know.
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From: Laurent Vivier lvivier@redhat.com
[ Upstream commit 24b2f5df86aaebbe7bac40304eaf5a146c02367c ]
The `tx_may_stop()` logic stops TX queues if free descriptors (`sq->vq->num_free`) fall below the threshold of (`MAX_SKB_FRAGS` + 2). If the total ring size (`ring_num`) is not strictly greater than this value, queues can become persistently stopped or stop after minimal use, severely degrading performance.
A single sk_buff transmission typically requires descriptors for: - The virtio_net_hdr (1 descriptor) - The sk_buff's linear data (head) (1 descriptor) - Paged fragments (up to MAX_SKB_FRAGS descriptors)
This patch enforces that the TX ring size ('ring_num') must be strictly greater than (MAX_SKB_FRAGS + 2). This ensures that the ring is always large enough to hold at least one maximally-fragmented packet plus at least one additional slot.
Reported-by: Lei Yang leiyang@redhat.com Signed-off-by: Laurent Vivier lvivier@redhat.com Reviewed-by: Xuan Zhuo xuanzhuo@linux.alibaba.com Acked-by: Jason Wang jasowang@redhat.com Link: https://patch.msgid.link/20250521092236.661410-4-lvivier@redhat.com Tested-by: Lei Yang leiyang@redhat.com Acked-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/virtio_net.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 0408c21bb1220..fb3908798458b 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3275,6 +3275,12 @@ static int virtnet_tx_resize(struct virtnet_info *vi, struct send_queue *sq, { int qindex, err;
+ if (ring_num <= MAX_SKB_FRAGS + 2) { + netdev_err(vi->dev, "tx size (%d) cannot be smaller than %d\n", + ring_num, MAX_SKB_FRAGS + 2); + return -EINVAL; + } + qindex = sq - vi->sq;
virtnet_tx_pause(vi, sq);