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virtio_pci: use irq to detect interrupt support 

commit 71491c54ea ("virtio_pci: don't try to use intxif pin is zero")
breaks virtio_pci on powerpc, when running as a qemu guest.

vp_find_vqs() bails out because pci_dev->pin == 0.

But pci_dev->irq is populated correctly, so vp_find_vqs_intx() would
succeed if we called it - which is what the code used to do.

This seems to happen because pci_dev->pin is not populated in
pci_assign_irq(). A PCI core bug? Maybe.

However Linus said:
	I really think that that is basically the only time you should use
	that 'pci_dev->pin' thing: it basically exists not for "does this
	device have an IRQ", but for "what is the routing of this irq on this
	device".

and
	The correct way to check for "no irq" doesn't use NO_IRQ at all, it just does
		if (dev->irq) ...

so let's just check irq and be done with it.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Fixes: 71491c54ea ("virtio_pci: don't try to use intxif pin is zero")
Cc: "Angus Chen" <angus.chen@jaguarmicro.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20221012220312.308522-1-mst@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2022-10-12 17:58:28 -04:00
parent 041bc24d86
commit 2145ab513e
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
drivers/virtio/virtio_pci_common.c
View File

@ -409,8 +409,8 @@ int vp_find_vqs(struct virtio_device *vdev, unsigned int nvqs,
err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, false, ctx, desc); err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, false, ctx, desc);
if (!err) if (!err)
return 0; return 0;
/* Is there an interrupt pin? If not give up. */ /* Is there an interrupt? If not give up. */
if (!(to_vp_device(vdev)->pci_dev->pin)) if (!(to_vp_device(vdev)->pci_dev->irq))
return err; return err;
/* Finally fall back to regular interrupts. */ /* Finally fall back to regular interrupts. */
return vp_find_vqs_intx(vdev, nvqs, vqs, callbacks, names, ctx); return vp_find_vqs_intx(vdev, nvqs, vqs, callbacks, names, ctx);