netdev - Re: [GIT PULL] virtio: fixes, features

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Message-ID: <87edvdm7qg.fsf@mpe.ellerman.id.au>
Date:   Thu, 13 Oct 2022 01:33:59 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        alvaro.karsz@...id-run.com, angus.chen@...uarmicro.com,
        gavinl@...dia.com, jasowang@...hat.com, lingshan.zhu@...el.com,
        wangdeming@...pur.com, xiujianfeng@...wei.com,
        linuxppc-dev@...ts.ozlabs.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [GIT PULL] virtio: fixes, features

Michael Ellerman <mpe@...erman.id.au> writes:
> [ Cc += Bjorn & linux-pci ]
>
> "Michael S. Tsirkin" <mst@...hat.com> writes:
>> On Wed, Oct 12, 2022 at 05:21:24PM +1100, Michael Ellerman wrote:
>>> "Michael S. Tsirkin" <mst@...hat.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@...hat.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.

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

cheers