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SubjectRE: [PATCH AUTOSEL 4.9 8/8] virtio_pci: don't try to use intxif pin is zero
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Hi sasha

> -----Original Message-----
> From: Sasha Levin <sashal@kernel.org>
> Sent: Tuesday, October 18, 2022 8:12 AM
> To: linux-kernel@vger.kernel.org; stable@vger.kernel.org
> Cc: Angus Chen <angus.chen@jaguarmicro.com>; Michael S . Tsirkin
> <mst@redhat.com>; Sasha Levin <sashal@kernel.org>; jasowang@redhat.com;
> virtualization@lists.linux-foundation.org
> Subject: [PATCH AUTOSEL 4.9 8/8] virtio_pci: don't try to use intxif pin is zero
>
> From: Angus Chen <angus.chen@jaguarmicro.com>
>
> [ Upstream commit 71491c54eafa318fdd24a1f26a1c82b28e1ac21d ]
>
> 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 printed 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
>
> The log :
> "genirq: Flags mismatch irq 0. 00000080 (virtio418) vs. 00015a00 (timer)"
> was printed because of the irq 0 is used by timer exclusive,and when
> vp_find_vqs call vp_find_vqs_msix and returns false twice (for
> whatever reason), then it will call vp_find_vqs_intx as a fallback.
> Because vp_dev->pci_dev->irq is zero, we request irq 0 with
> flag IRQF_SHARED, and get a backtrace like above.
>
> According to PCI spec about "Interrupt Pin" Register (Offset 3Dh):
> "The Interrupt Pin register is a read-only register that identifies the
> legacy interrupt Message(s) the Function uses. Valid values are 01h, 02h,
> 03h, and 04h that map to legacy interrupt Messages for INTA,
> INTB, INTC, and INTD respectively. A value of 00h indicates that the
> Function uses no legacy interrupt Message(s)."
>
> So if vp_dev->pci_dev->pin is zero, we should not request legacy
> interrupt.
>
> Signed-off-by: Angus Chen <angus.chen@jaguarmicro.com>
> Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> Message-Id: <20220930000915.548-1-angus.chen@jaguarmicro.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> drivers/virtio/virtio_pci_common.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/virtio/virtio_pci_common.c
> b/drivers/virtio/virtio_pci_common.c
> index 37e3ba5dadf6..d634eb926a2f 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -389,6 +389,9 @@ int vp_find_vqs(struct virtio_device *vdev, unsigned
> nvqs,
> true, false);
> if (!err)
> return 0;
> + /* Is there an interrupt pin? If not give up. */
> + if (!(to_vp_device(vdev)->pci_dev->pin))
> + return err;
> /* Finally fall back to regular interrupts. */
> return vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
> false, false);
> --
> 2.35.1

the patch 71491c54eafa31 has been fixed by 2145ab513e3b3,
It is report by Michael Ellerman <mpe@ellerman.id.au> and suggested by linus.
If it is merged in the stable git repo, I worry about powerpc arch.
Thans.

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