On Tue, Nov 26, 2024 at 10:42 AM Koichiro Den
<koichiro.den@xxxxxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxxxxxxx> # v6.11+
> Signed-off-by: Koichiro Den <koichiro.den@xxxxxxxxxxxxx>
> ---
> 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);
> }
Are we sure this can drain the queue? Note that the device is not stopped.
>
> /* 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
>
>
Thanks
