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Message-ID: <CACGkMEvR4+_iRAFACkXLgX-hGwjfOgd3emiyquzxUHL9wC-b=g@mail.gmail.com>
Date: Wed, 27 Nov 2024 11:24:15 +0800
From: Jason Wang <jasowang@...hat.com>
To: Koichiro Den <koichiro.den@...onical.com>
Cc: virtualization@...ts.linux.dev, mst@...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: Re: [PATCH] virtio_net: drain unconsumed tx completions if any before dql_reset
On Tue, Nov 26, 2024 at 12:44 PM Koichiro Den
<koichiro.den@...onical.com> wrote:
>
> On Tue, Nov 26, 2024 at 11:50:17AM +0800, Jason Wang wrote:
> > On Tue, Nov 26, 2024 at 10:42 AM Koichiro Den
> > <koichiro.den@...onical.com> 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@...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);
> > > }
> >
> > Are we sure this can drain the queue? Note that the device is not stopped.
>
> Thanks for reviewing. netif_tx_wake_queue can be invoked before the "drain"
> point I added e.g. via virtnet_config_changed_work, so it seems that I need
> to ensure it's stopped (DRV_XOFF) before the "drain" and wake it afterwards.
> Please let me know if I’m mistaken.
Not sure I get you, but I meant we don't reset the device so it can
keep raising tx interrupts:
virtnet_drain_old_xmit()
netdev_tx_reset_queue()
skb_xmit_done()
napi_enable()
netdev_tx_completed_queue() // here we might still surprise the bql?
Thanks
>
> >
> > >
> > > /* 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
> >
>
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