On Thu, Oct 13, 2022 at 01:33:59AM +1100, Michael Ellerman wrote:

Michael Ellerman [off-list ref] writes:

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[ Cc += Bjorn & linux-pci ]

"Michael S. Tsirkin" [off-list ref] writes:

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On Wed, Oct 12, 2022 at 05:21:24PM +1100, Michael Ellerman wrote:

quoted

"Michael S. Tsirkin" [off-list ref] writes:

...

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----------------------------------------------------------------
virtio: fixes, features

9k mtu perf improvements
vdpa feature provisioning
virtio blk SECURE ERASE support

Fixes, cleanups all over the place.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

----------------------------------------------------------------
Alvaro Karsz (1):
      virtio_blk: add SECURE ERASE command support

Angus Chen (1):
      virtio_pci: don't try to use intxif pin is zero

This commit breaks virtio_pci for me 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.

I think this happens because pci_dev->pin is not populated in
pci_assign_irq().

I would absolutely believe this is bug in our PCI code, but I think it
may also affect other platforms that use of_irq_parse_and_map_pci().

How about fixing this in of_irq_parse_and_map_pci then?
Something like the below maybe?

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index 196834ed44fe..504c4d75c83f 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c

@@ -446,6 +446,8 @@ static int of_irq_parse_pci(const struct pci_dev *pdev, struct of_phandle_args *
 	if (pin == 0)
 		return -ENODEV;
 
+	pdev->pin = pin;
+
 	/* Local interrupt-map in the device node? Use it! */
 	if (of_get_property(dn, "interrupt-map", NULL)) {
 		pin = pci_swizzle_interrupt_pin(pdev, pin);

Backing up a bit. Should the virtio code be looking at pci_dev->pin in
the first place?

Shouldn't it be checking pci_dev->irq instead?

The original commit talks about irq being 0 and colliding with the timer
interrupt.

But all (most?) platforms have converged on 0 meaning NO_IRQ since quite
a fews ago AFAIK.

Are you sure?

arch/arm/include/asm/irq.h:#ifndef NO_IRQ
arch/arm/include/asm/irq.h:#define NO_IRQ       ((unsigned int)(-1))

And the timer irq == 0 is a special case AIUI:
  https://lore.kernel.org/all/CA+55aFwiLp1z+2mzkrFsid1WZQ0TQkcn8F2E6NL_AVR+m1fZ2w@mail.gmail.com/ (local)

cheers