Message-ID: <20241126024200.2371546-1-koichiro.den@canonical.com>
Date: Tue, 26 Nov 2024 11:42:00 +0900
From: Koichiro Den <koichiro.den@...onical.com>
To: virtualization@...ts.linux.dev
Cc: mst@...hat.com,
	jasowang@...hat.com,
	xuanzhuo@...ux.alibaba.com,
	eperezma@...hat.com,
	andrew+netdev@...n.ch,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: [PATCH] virtio_net: drain unconsumed tx completions if any before dql_reset

When virtnet_close is followed by virtnet_open, there is a slight chance
that some TX completions remain unconsumed. Those are handled during the
first NAPI poll, but since dql_reset occurs just beforehand, it can lead
to a crash [1].

This issue can be reproduced by running: `while :; do ip l set DEV down;
ip l set DEV up; done` under heavy network TX load from inside of the
machine.

To fix this, drain unconsumed TX completions if any before dql_reset,
allowing BQL to start cleanly.

------------[ cut here ]------------
kernel BUG at lib/dynamic_queue_limits.c:99!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
CPU: 7 UID: 0 PID: 1598 Comm: ip Tainted: G    N 6.12.0net-next_main+ #2
Tainted: [N]=TEST
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), \
BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
RIP: 0010:dql_completed+0x26b/0x290
Code: b7 c2 49 89 e9 44 89 da 89 c6 4c 89 d7 e8 ed 17 47 00 58 65 ff 0d
4d 27 90 7e 0f 85 fd fe ff ff e8 ea 53 8d ff e9 f3 fe ff ff <0f> 0b 01
d2 44 89 d1 29 d1 ba 00 00 00 00 0f 48 ca e9 28 ff ff ff
RSP: 0018:ffffc900002b0d08 EFLAGS: 00010297
RAX: 0000000000000000 RBX: ffff888102398c80 RCX: 0000000080190009
RDX: 0000000000000000 RSI: 000000000000006a RDI: 0000000000000000
RBP: ffff888102398c00 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000000ca R11: 0000000000015681 R12: 0000000000000001
R13: ffffc900002b0d68 R14: ffff88811115e000 R15: ffff8881107aca40
FS:  00007f41ded69500(0000) GS:ffff888667dc0000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000556ccc2dc1a0 CR3: 0000000104fd8003 CR4: 0000000000772ef0
PKRU: 55555554
Call Trace:
 <IRQ>
 ? die+0x32/0x80
 ? do_trap+0xd9/0x100
 ? dql_completed+0x26b/0x290
 ? dql_completed+0x26b/0x290
 ? do_error_trap+0x6d/0xb0
 ? dql_completed+0x26b/0x290
 ? exc_invalid_op+0x4c/0x60
 ? dql_completed+0x26b/0x290
 ? asm_exc_invalid_op+0x16/0x20
 ? dql_completed+0x26b/0x290
 __free_old_xmit+0xff/0x170 [virtio_net]
 free_old_xmit+0x54/0xc0 [virtio_net]
 virtnet_poll+0xf4/0xe30 [virtio_net]
 ? __update_load_avg_cfs_rq+0x264/0x2d0
 ? update_curr+0x35/0x260
 ? reweight_entity+0x1be/0x260
 __napi_poll.constprop.0+0x28/0x1c0
 net_rx_action+0x329/0x420
 ? enqueue_hrtimer+0x35/0x90
 ? trace_hardirqs_on+0x1d/0x80
 ? kvm_sched_clock_read+0xd/0x20
 ? sched_clock+0xc/0x30
 ? kvm_sched_clock_read+0xd/0x20
 ? sched_clock+0xc/0x30
 ? sched_clock_cpu+0xd/0x1a0
 handle_softirqs+0x138/0x3e0
 do_softirq.part.0+0x89/0xc0
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0xa7/0xb0
 virtnet_open+0xc8/0x310 [virtio_net]
 __dev_open+0xfa/0x1b0
 __dev_change_flags+0x1de/0x250
 dev_change_flags+0x22/0x60
 do_setlink.isra.0+0x2df/0x10b0
 ? rtnetlink_rcv_msg+0x34f/0x3f0
 ? netlink_rcv_skb+0x54/0x100
 ? netlink_unicast+0x23e/0x390
 ? netlink_sendmsg+0x21e/0x490
 ? ____sys_sendmsg+0x31b/0x350
 ? avc_has_perm_noaudit+0x67/0xf0
 ? cred_has_capability.isra.0+0x75/0x110
 ? __nla_validate_parse+0x5f/0xee0
 ? __pfx___probestub_irq_enable+0x3/0x10
 ? __create_object+0x5e/0x90
 ? security_capable+0x3b/0x70
 rtnl_newlink+0x784/0xaf0
 ? avc_has_perm_noaudit+0x67/0xf0
 ? cred_has_capability.isra.0+0x75/0x110
 ? stack_depot_save_flags+0x24/0x6d0
 ? __pfx_rtnl_newlink+0x10/0x10
 rtnetlink_rcv_msg+0x34f/0x3f0
 ? do_syscall_64+0x6c/0x180
 ? entry_SYSCALL_64_after_hwframe+0x76/0x7e
 ? __pfx_rtnetlink_rcv_msg+0x10/0x10
 netlink_rcv_skb+0x54/0x100
 netlink_unicast+0x23e/0x390
 netlink_sendmsg+0x21e/0x490
 ____sys_sendmsg+0x31b/0x350
 ? copy_msghdr_from_user+0x6d/0xa0
 ___sys_sendmsg+0x86/0xd0
 ? __pte_offset_map+0x17/0x160
 ? preempt_count_add+0x69/0xa0
 ? __call_rcu_common.constprop.0+0x147/0x610
 ? preempt_count_add+0x69/0xa0
 ? preempt_count_add+0x69/0xa0
 ? _raw_spin_trylock+0x13/0x60
 ? trace_hardirqs_on+0x1d/0x80
 __sys_sendmsg+0x66/0xc0
 do_syscall_64+0x6c/0x180
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f41defe5b34
Code: 15 e1 12 0f 00 f7 d8 64 89 02 b8 ff ff ff ff eb bf 0f 1f 44 00 00
f3 0f 1e fa 80 3d 35 95 0f 00 00 74 13 b8 2e 00 00 00 0f 05 <48> 3d 00
f0 ff ff 77 4c c3 0f 1f 00 55 48 89 e5 48 83 ec 20 89 55
RSP: 002b:00007ffe5336ecc8 EFLAGS: 00000202 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f41defe5b34
RDX: 0000000000000000 RSI: 00007ffe5336ed30 RDI: 0000000000000003
RBP: 00007ffe5336eda0 R08: 0000000000000010 R09: 0000000000000001
R10: 00007ffe5336f6f9 R11: 0000000000000202 R12: 0000000000000003
R13: 0000000067452259 R14: 0000556ccc28b040 R15: 0000000000000000
 </TASK>
[...]
---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---

Fixes: c8bd1f7f3e61 ("virtio_net: add support for Byte Queue Limits")
Cc: <stable@...r.kernel.org> # v6.11+
Signed-off-by: Koichiro Den <koichiro.den@...onical.com>
---
 drivers/net/virtio_net.c | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 64c87bb48a41..3e36c0470600 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -513,7 +513,7 @@ static struct sk_buff *virtnet_skb_append_frag(struct sk_buff *head_skb,
 					       struct sk_buff *curr_skb,
 					       struct page *page, void *buf,
 					       int len, int truesize);
-static void virtnet_xsk_completed(struct send_queue *sq, int num);
+static void virtnet_xsk_completed(struct send_queue *sq, int num, bool drain);
 
 enum virtnet_xmit_type {
 	VIRTNET_XMIT_TYPE_SKB,
@@ -580,7 +580,8 @@ static void sg_fill_dma(struct scatterlist *sg, dma_addr_t addr, u32 len)
 }
 
 static void __free_old_xmit(struct send_queue *sq, struct netdev_queue *txq,
-			    bool in_napi, struct virtnet_sq_free_stats *stats)
+			    bool in_napi, struct virtnet_sq_free_stats *stats,
+			    bool drain)
 {
 	struct xdp_frame *frame;
 	struct sk_buff *skb;
@@ -620,7 +621,8 @@ static void __free_old_xmit(struct send_queue *sq, struct netdev_queue *txq,
 			break;
 		}
 	}
-	netdev_tx_completed_queue(txq, stats->napi_packets, stats->napi_bytes);
+	if (!drain)
+		netdev_tx_completed_queue(txq, stats->napi_packets, stats->napi_bytes);
 }
 
 static void virtnet_free_old_xmit(struct send_queue *sq,
@@ -628,10 +630,21 @@ static void virtnet_free_old_xmit(struct send_queue *sq,
 				  bool in_napi,
 				  struct virtnet_sq_free_stats *stats)
 {
-	__free_old_xmit(sq, txq, in_napi, stats);
+	__free_old_xmit(sq, txq, in_napi, stats, false);
 
 	if (stats->xsk)
-		virtnet_xsk_completed(sq, stats->xsk);
+		virtnet_xsk_completed(sq, stats->xsk, false);
+}
+
+static void virtnet_drain_old_xmit(struct send_queue *sq,
+				   struct netdev_queue *txq)
+{
+	struct virtnet_sq_free_stats stats = {0};
+
+	__free_old_xmit(sq, txq, false, &stats, true);
+
+	if (stats.xsk)
+		virtnet_xsk_completed(sq, stats.xsk, true);
 }
 
 /* Converting between virtqueue no. and kernel tx/rx queue no.
@@ -1499,7 +1512,8 @@ static bool virtnet_xsk_xmit(struct send_queue *sq, struct xsk_buff_pool *pool,
 	/* Avoid to wakeup napi meanless, so call __free_old_xmit instead of
 	 * free_old_xmit().
 	 */
-	__free_old_xmit(sq, netdev_get_tx_queue(dev, sq - vi->sq), true, &stats);
+	__free_old_xmit(sq, netdev_get_tx_queue(dev, sq - vi->sq), true,
+			&stats, false);
 
 	if (stats.xsk)
 		xsk_tx_completed(sq->xsk_pool, stats.xsk);
@@ -1556,10 +1570,13 @@ static int virtnet_xsk_wakeup(struct net_device *dev, u32 qid, u32 flag)
 	return 0;
 }
 
-static void virtnet_xsk_completed(struct send_queue *sq, int num)
+static void virtnet_xsk_completed(struct send_queue *sq, int num, bool drain)
 {
 	xsk_tx_completed(sq->xsk_pool, num);
 
+	if (drain)
+		return;
+
 	/* If this is called by rx poll, start_xmit and xdp xmit we should
 	 * wakeup the tx napi to consume the xsk tx queue, because the tx
 	 * interrupt may not be triggered.
@@ -3041,6 +3058,7 @@ static void virtnet_disable_queue_pair(struct virtnet_info *vi, int qp_index)
 
 static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
 {
+	struct netdev_queue *txq = netdev_get_tx_queue(vi->dev, qp_index);
 	struct net_device *dev = vi->dev;
 	int err;
 
@@ -3054,7 +3072,10 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index)
 	if (err < 0)
 		goto err_xdp_reg_mem_model;
 
-	netdev_tx_reset_queue(netdev_get_tx_queue(vi->dev, qp_index));
+	/* Drain any unconsumed TX skbs transmitted before the last virtnet_close */
+	virtnet_drain_old_xmit(&vi->sq[qp_index], txq);
+
+	netdev_tx_reset_queue(txq);
 	virtnet_napi_enable(vi->rq[qp_index].vq, &vi->rq[qp_index].napi);
 	virtnet_napi_tx_enable(vi, vi->sq[qp_index].vq, &vi->sq[qp_index].napi);
 
-- 
2.43.0

Powered by blists - more mailing lists