* Re: [PATCH v2] virtio_pci: avoid to request intx irq if pin is zero
[not found] <20220928053522.440-1-angus.chen@jaguarmicro.com>
@ 2022-09-28 5:59 ` Michael S. Tsirkin
0 siblings, 0 replies; only message in thread
From: Michael S. Tsirkin @ 2022-09-28 5:59 UTC (permalink / raw)
To: Angus Chen; +Cc: linux-kernel, virtualization
Thanks! More minor issues to address
On Wed, Sep 28, 2022 at 01:35:22PM +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
>
> 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 call vp_find_vqs_msix and return false twice for
> whatever reason,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,we will get a backtrace like above.
>
> according to PCI spec , Devices (or device functions)
> that do not use an interrupt pin must put a 0 in this register.
Pls add quotes and add "Interrupt Pin:" to make it clear in which register.
> So if vp_dev->pci_dev->pin is zero, maybe we should not request legacy
> interrupt.
and drop "maybe" here pls. I guess it sounds impolite to you but
as the patch author you get to make the tough decisions :)
>
> Signed-off-by: Angus Chen <angus.chen@jaguarmicro.com>
> Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> v2:
> - Decide whether to request an intx interrupt by pin instead of irq
> - suggested by mst
>
> v1:https://lore.kernel.org/virtualization/20220928000228-mutt-send-email-mst@kernel.org/T/#u
>
> 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 ad258a9d3b9f..81225e503e69 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -362,6 +362,9 @@ static int vp_find_vqs_intx(struct virtio_device *vdev, unsigned int nvqs,
> struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> int i, err, queue_idx = 0;
>
> + if (vp_dev->pci_dev->pin == 0)
> + return -EINVAL;
> +
Pls use !pin for brevity.
> vp_dev->vqs = kcalloc(nvqs, sizeof(*vp_dev->vqs), GFP_KERNEL);
> if (!vp_dev->vqs)
> return -ENOMEM;
So, this is mostly ok. The only issue is this:
int vp_find_vqs(struct virtio_device *vdev, unsigned int nvqs,
struct virtqueue *vqs[], vq_callback_t *callbacks[],
const char * const names[], const bool *ctx,
struct irq_affinity *desc)
{
int err;
/* Try MSI-X with one vector per queue. */
err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, true, ctx, desc);
if (!err)
return 0;
/* Fallback: MSI-X with one vector for config, one shared for queues. */
err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, false, ctx, desc);
if (!err)
return 0;
/* Finally fall back to regular interrupts. */
return vp_find_vqs_intx(vdev, nvqs, vqs, callbacks, names, ctx);
}
So the real source of failure to use msix, will be overwritten in err by EINVAL.
How about moving the "if" to vp_find_vqs?
E.g.
/* Is there an interrupt pin? If not give up. */
if (!vdev->pci_dev->pin)
return err;
> --
> 2.17.1
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