Date:   Wed, 28 Sep 2022 03:25:12 +0000
From:   Angus Chen <angus.chen@...uarmicro.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
CC:     "jasowang@...hat.com" <jasowang@...hat.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Liming Wu <liming.wu@...uarmicro.com>,
        "stefanha@...hat.com" <stefanha@...hat.com>,
        Christoph Hellwig <hch@....de>
Subject: RE: [PATCH v1] virtio_blk: should not use IRQD_AFFINITY_MANAGED in
 init_rq



> -----Original Message-----
> From: Michael S. Tsirkin <mst@...hat.com>
> Sent: Wednesday, September 28, 2022 4:47 AM
> To: Angus Chen <angus.chen@...uarmicro.com>
> Cc: jasowang@...hat.com; pbonzini@...hat.com; axboe@...nel.dk;
> virtualization@...ts.linux-foundation.org; linux-block@...r.kernel.org;
> linux-kernel@...r.kernel.org; Liming Wu <liming.wu@...uarmicro.com>;
> stefanha@...hat.com; Christoph Hellwig <hch@....de>
> Subject: Re: [PATCH v1] virtio_blk: should not use IRQD_AFFINITY_MANAGED in
> init_rq
> 
> On Sat, Sep 24, 2022 at 11:48:54AM +0800, Angus Chen wrote:
> > The background is that we use dpu in cloud computing,the arch is x86,80
> > cores.We will have a lots of virtio devices,like 512 or more.
> > When we probe about 200 virtio_blk devices,it will fail and
> > the stack is print as follows:
> >
> > [25338.485128] virtio-pci 0000:b3:00.0: virtio_pci: leaving for legacy driver
> > [25338.496174] genirq: Flags mismatch irq 0. 00000080 (virtio418) vs.
> 00015a00 (timer)
> > [25338.503822] CPU: 20 PID: 5431 Comm: kworker/20:0 Kdump: loaded
> Tainted: G           OE    --------- -  - 4.18.0-305.30.1.el8.x86_64
> > [25338.516403] Hardware name: Inspur NF5280M5/YZMB-00882-10E, BIOS
> 4.1.21 08/25/2021
> > [25338.523881] Workqueue: events work_for_cpu_fn
> > [25338.528235] Call Trace:
> > [25338.530687]  dump_stack+0x5c/0x80
> > [25338.534000]  __setup_irq.cold.53+0x7c/0xd3
> > [25338.538098]  request_threaded_irq+0xf5/0x160
> > [25338.542371]  vp_find_vqs+0xc7/0x190
> > [25338.545866]  init_vq+0x17c/0x2e0 [virtio_blk]
> > [25338.550223]  ? ncpus_cmp_func+0x10/0x10
> > [25338.554061]  virtblk_probe+0xe6/0x8a0 [virtio_blk]
> > [25338.558846]  virtio_dev_probe+0x158/0x1f0
> > [25338.562861]  really_probe+0x255/0x4a0
> > [25338.566524]  ? __driver_attach_async_helper+0x90/0x90
> > [25338.571567]  driver_probe_device+0x49/0xc0
> > [25338.575660]  bus_for_each_drv+0x79/0xc0
> > [25338.579499]  __device_attach+0xdc/0x160
> > [25338.583337]  bus_probe_device+0x9d/0xb0
> > [25338.587167]  device_add+0x418/0x780
> > [25338.590654]  register_virtio_device+0x9e/0xe0
> > [25338.595011]  virtio_pci_probe+0xb3/0x140
> > [25338.598941]  local_pci_probe+0x41/0x90
> > [25338.602689]  work_for_cpu_fn+0x16/0x20
> > [25338.606443]  process_one_work+0x1a7/0x360
> > [25338.610456]  ? create_worker+0x1a0/0x1a0
> > [25338.614381]  worker_thread+0x1cf/0x390
> > [25338.618132]  ? create_worker+0x1a0/0x1a0
> > [25338.622051]  kthread+0x116/0x130
> > [25338.625283]  ? kthread_flush_work_fn+0x10/0x10
> > [25338.629731]  ret_from_fork+0x1f/0x40
> > [25338.633395] virtio_blk: probe of virtio418 failed with error -16
> >
> > After I did some work of this stack,took stap and crash to get more
> > information,I found that the auto irq_affinity affect this.
> > When "vp_find_vqs" call "vp_find_vqs_msix" failed,it will be go back
> > to call vp_find_vqs_msix again with ctx be false, and when it failed again,
> > we will call vp_find_vqs_intx,if the vp_dev->pci_dev->irq is zero,
> > we will get a backtrace like above.
> >
> > The log :
> > "genirq: Flags mismatch irq 0. 00000080 (virtio418) vs. 00015a00 (timer)"
> > was print because of the irq 0 is used by timer exclusive,and when
> > vp_find_vqs called vp_find_vqs_msix and return false twice,then it will
> > call vp_find_vqs_intx for the last try.
> > Because vp_dev->pci_dev->irq is zero,so it will be request irq 0 with
> > flag IRQF_SHARED.
> 
> First this is a bug. We can fix that so it will fail more cleanly.
> 
> We should check pci_dev->pin and if 0 do not try to use INT#x
> at all.
Yes, I will send a patch for this only.
Thank you.
> It will still fail, just with a nicer backtrace.
> 
> 
> 
> 
> > without config CONFIG_GENERIC_IRQ_DEBUGFS,
> > I found that we called vp_find_vqs_msix failed twice because of
> > the irq resource was exhausted.
> 
> I see. I don't know enough about how this work, but roughly
> I think the issue is at a high level
> 
> - because of auto affinity, we try to reserve an interrupt on all CPUs
> - as there are 512 devices with a single vector per VQ we would
>   have no issue as they would be spread between CPUs,
>   but allocating on all CPUs fails.
> 
> 
> I don't think the issue should be fixed at blk level - it is not
> blk specifix - but yes this looks like a problem.
> Christoph, any idea?
> 
> 
> 
> > crash> irq_domain.name,parent 0xffff9bff87d4dec0
> >   name = 0xffff9bff87c1fd60 "INTEL-IR-MSI-1-2"
> >   parent = 0xffff9bff87400000
> > crash> irq_domain.name,parent 0xffff9bff87400000
> >   name = 0xffff9bff87c24300 "INTEL-IR-1"
> >   parent = 0xffff9bff87c6c900
> > crash> irq_domain.name,parent 0xffff9bff87c6c900
> >   name = 0xffff9bff87c3ecd0 "VECTOR"
> >   parent = 0x0----------------------the highest level
> >
> > and stap irq_matrix_alloc_managed get return value -ENOSPC.
> >
> > When no virtio_blk device probe,the vctor_matrix is:
> > crash>  p *vector_matrix
> > $1 = {
> >   matrix_bits = 256,
> >   alloc_start = 32,
> >   alloc_end = 236,
> >   alloc_size = 204,
> >   global_available = 15593,
> >   global_reserved = 149,
> >   systembits_inalloc = 3,
> >   total_allocated = 409,
> >   online_maps = 80,
> >   maps = 0x2ff20,
> >   scratch_map = {1161063342014463, 0, 1, 18446726481523507200,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
> >   system_map = {1125904739729407, 0, 1, 18446726481523507200,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
> > }
> >
> > When the dump stack occur,the vector_matrix of system is exhausted.
> > crash> p *vector_matrix
> > $82 = {
> >   matrix_bits = 256,
> >   alloc_start = 32,
> >   alloc_end = 236,
> >   alloc_size = 204,
> >   global_available = 0,//caq:irq left
> >   global_reserved = 151,
> >   systembits_inalloc = 3,
> >   total_allocated = 1922,//caq:irq that allocated
> >   online_maps = 80,
> >   maps = 0x2ff20,
> >   scratch_map = {18446744069952503807, 18446744073709551615,
> >  18446744073709551615, 18446735277616529407, 0, 0, 0, 0, 0,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
> >   system_map = {1125904739729407, 0, 1, 18446726481523507200,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
> > }
> >
> > And we tested the virtio_blk device which request irq success,
> > we found that in a system with 80 cores and two numa ,one
> > virtio_blk device with just two data queues consume 81 irqs capacity,
> > Although it just only three irqs in /proc/interrupt,80 irqs capacity
> > is effected by function "irq_build_affinity_masks" with 2*40.
> >
> > before one virtio_blk device hotplug out:
> > crash> p *vector_matrix
> > $2 = {
> >   matrix_bits = 256,
> >   alloc_start = 32,
> >   alloc_end = 236,
> >   alloc_size = 204,
> >   global_available = 15215,
> >   global_reserved = 150,
> >   systembits_inalloc = 3,
> >   total_allocated = 553,
> >   online_maps = 80,
> >   maps = 0x2ff20,
> >   scratch_map = {1179746449752063, 0, 1, 18446726481523507200, 0, 0, 0,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> >  0, 0, 0, 0, 0},
> >   system_map = {1125904739729407, 0, 1, 18446726481523507200, 0, 0, 0,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> >  0, 0, 0, 0, 0}
> > }
> >
> > after one virtio_blk device hotplug out:
> > crash> p *vector_matrix
> > $3 = {
> >   matrix_bits = 256,
> >   alloc_start = 32,
> >   alloc_end = 236,
> >   alloc_size = 204,
> >   global_available = 15296,---it increase 81,include 1 config irq.
> >   global_reserved = 150,
> >   systembits_inalloc = 3,
> >   total_allocated = 550,------it just decrease 3.
> >   online_maps = 80,
> >   maps = 0x2ff20,
> >   scratch_map = {481036337152, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> >  0, 0, 0, 0},
> >   system_map = {1125904739729407, 0, 1, 18446726481523507200, 0, 0, 0,
> >  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> >  0, 0, 0, 0, 0}
> > }
> >
> > We test the new kernel also,it occur the same result.
> > [Fri Sep 23 04:51:42 2022] genirq: Flags mismatch irq 0. 00000080 (virtio608)
> vs. 00015a00 (timer)
> > [Fri Sep 23 04:51:42 2022] CPU: 0 PID: 5749 Comm: kworker/0:0 Kdump:
> loaded Tainted: G        W  OE      6.0.0-rc6+ #5
> > [Fri Sep 23 04:51:42 2022] Hardware name: Inspur
> NF5280M5/YZMB-00882-10E, BIOS 4.1.19 06/16/2021
> > [Fri Sep 23 04:51:42 2022] Workqueue: events work_for_cpu_fn
> > [Fri Sep 23 04:51:42 2022] Call Trace:
> > [Fri Sep 23 04:51:42 2022]  <TASK>
> > [Fri Sep 23 04:51:42 2022]  dump_stack_lvl+0x33/0x46
> > [Fri Sep 23 04:51:42 2022]  __setup_irq+0x705/0x770
> > [Fri Sep 23 04:51:42 2022]  request_threaded_irq+0x109/0x170
> > [Fri Sep 23 04:51:42 2022]  vp_find_vqs+0xc4/0x190
> > [Fri Sep 23 04:51:42 2022]  init_vqs+0x348/0x580 [virtio_net]
> > [Fri Sep 23 04:51:42 2022]  virtnet_probe+0x54d/0xa80 [virtio_net]
> > [Fri Sep 23 04:51:42 2022]  virtio_dev_probe+0x19c/0x240
> > [Fri Sep 23 04:51:42 2022]  really_probe+0x106/0x3e0
> > [Fri Sep 23 04:51:42 2022]  ? pm_runtime_barrier+0x4f/0xa0
> > [Fri Sep 23 04:51:42 2022]  __driver_probe_device+0x79/0x170
> > [Fri Sep 23 04:51:42 2022]  driver_probe_device+0x1f/0xa0
> > [Fri Sep 23 04:51:42 2022]  __device_attach_driver+0x85/0x110
> > [Fri Sep 23 04:51:42 2022]  ? driver_allows_async_probing+0x60/0x60
> > [Fri Sep 23 04:51:42 2022]  ? driver_allows_async_probing+0x60/0x60
> > [Fri Sep 23 04:51:42 2022]  bus_for_each_drv+0x67/0xb0
> > [Fri Sep 23 04:51:42 2022]  __device_attach+0xe9/0x1b0
> > [Fri Sep 23 04:51:42 2022]  bus_probe_device+0x87/0xa0
> > [Fri Sep 23 04:51:42 2022]  device_add+0x59f/0x950
> > [Fri Sep 23 04:51:42 2022]  ? dev_set_name+0x4e/0x70
> > [Fri Sep 23 04:51:42 2022]  register_virtio_device+0xac/0xf0
> > [Fri Sep 23 04:51:42 2022]  virtio_pci_probe+0x101/0x170
> > [Fri Sep 23 04:51:42 2022]  local_pci_probe+0x42/0xa0
> > [Fri Sep 23 04:51:42 2022]  work_for_cpu_fn+0x13/0x20
> > [Fri Sep 23 04:51:42 2022]  process_one_work+0x1c2/0x3d0
> > [Fri Sep 23 04:51:42 2022]  ? process_one_work+0x3d0/0x3d0
> > [Fri Sep 23 04:51:42 2022]  worker_thread+0x1b9/0x360
> > [Fri Sep 23 04:51:42 2022]  ? process_one_work+0x3d0/0x3d0
> > [Fri Sep 23 04:51:42 2022]  kthread+0xe6/0x110
> > [Fri Sep 23 04:51:42 2022]  ? kthread_complete_and_exit+0x20/0x20
> > [Fri Sep 23 04:51:42 2022]  ret_from_fork+0x1f/0x30
> > [Fri Sep 23 04:51:42 2022]  </TASK>
> > [Fri Sep 23 04:51:43 2022] virtio_net: probe of virtio608 failed with error -16
> >
> > Fixes: ad71473d9c43 ("virtio_blk: use virtio IRQ affinity")
> > Signed-off-by: Angus Chen <angus.chen@...uarmicro.com>
> > Tested-by: Liming Wu <liming.wu@...uarmicro.com>
> > ---
> >  drivers/block/virtio_blk.c | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> > index a8bcf3f664af..075de30a9bb4 100644
> > --- a/drivers/block/virtio_blk.c
> > +++ b/drivers/block/virtio_blk.c
> > @@ -513,7 +513,6 @@ static int init_vq(struct virtio_blk *vblk)
> >  	struct virtqueue **vqs;
> >  	unsigned short num_vqs;
> >  	struct virtio_device *vdev = vblk->vdev;
> > -	struct irq_affinity desc = { 0, };
> >
> >  	err = virtio_cread_feature(vdev, VIRTIO_BLK_F_MQ,
> >  				   struct virtio_blk_config, num_queues,
> > @@ -548,7 +547,7 @@ static int init_vq(struct virtio_blk *vblk)
> >  	}
> >
> >  	/* Discover virtqueues and write information to configuration.  */
> > -	err = virtio_find_vqs(vdev, num_vqs, vqs, callbacks, names, &desc);
> > +	err = virtio_find_vqs(vdev, num_vqs, vqs, callbacks, names, NULL);
> >  	if (err)
> >  		goto out;
> >
> > --
> > 2.17.1

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