Virtualization - Oct 2022 - [GIT PULL] virtio: fixes, features

On Thu, Oct 13, 2022 at 01:33:59AM +1100, Michael Ellerman
wrote:
> Michael Ellerman <mpe at ellerman.id.au> writes:
> > [ Cc += Bjorn & linux-pci ]
> >
> > "Michael S. Tsirkin" <mst at redhat.com> writes:
> >> On Wed, Oct 12, 2022 at 05:21:24PM +1100, Michael Ellerman wrote:
> >>> "Michael S. Tsirkin" <mst at redhat.com>
writes:
> > ...
> >>> >
----------------------------------------------------------------
> >>> > 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 at
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
at mail.gmail.com/
> 
> cheers

On Wed, Oct 12, 2022 at 8:51 AM Michael S. Tsirkin <mst at redhat.com>
wrote:
>
> Are you sure?
MichaelE is right.

This is just bogus historical garbage:
> arch/arm/include/asm/irq.h:#ifndef NO_IRQ
> arch/arm/include/asm/irq.h:#define NO_IRQ       ((unsigned int)(-1))
that I've tried to get rid of for years, but for some reason it just
won't die.

NO_IRQ should be zero. Or rather, it shouldn't exist at all. It's a
bogus thing.

You can see just how bogus it is from grepping for it - the users are
all completely and utterly confused, and all are entirely historical
brokenness.

The correct way to check for "no irq" doesn't use NO_IRQ at all,
it just does

        if (dev->irq) ...

which is why you will only find a few instances of NO_IRQ in the tree
in the first place.

The NO_IRQ thing is mainly actually defined by a few drivers that just
never got converted to the proper world order, and even then you can
see the confusion (ie some drivers use "-1", others use "0",
and yet
others use "((unsigned int)(-1)".

                   Linus