Re: [PATCH] pci-hyperv: Use only 16 bit integer for PCI domain

John Hubbard
2017-04-25T18:19:13Z

On Tue, 25 Apr 2017, Christoph Hellwig wrote:

> Hi John,
>
> please fix your quoting of the previous mails, thanks!

Shoot, sorry about any quoting issues. I'm sufficiently new to conversing
on these lists that I'm not even sure which mistake I made.

>
>
> What ACPI defines does not matter at all. Linux uses 32-bit domains
> IDs, and on x86 specifily uses those for non-ACPI enumarated domains
> (e.g. VMD).
>
> You've also not demontrated any issue with any Linux driver yet.

The NVIDIA out-of-tree driver has historically treated domains as 16-bit.
So this showed up when people tried to run that driver in a hyper-v VM.

>
> > Also...it would be nice if we could use Haiyang's patch as at least a
> > temporary fix, because distros are just today releasing the previous code,
> > and HyperV will start breaking "occasionally", depending on whether the
> > 32-bit virtual (fake) PCI domain fits within 16 bits. (If not, then we can
> > rush out a driver update to fix it, but there will be a window of time with
> > some breakage there.)
>
> Just send the fix to whatever driver is broken to the driver maintainer.

Done: that would be us. :)

> But I can't find a single broken driver in the tree, and as you know
> nothing else matters for Linux anyway.
>

Yes, I looked at Nouveau, and I see that they allow for a 32-bit domain,
so I agree that we haven't found any in-tree drivers that have a problem.

Anyway, thanks for the answers and explanations.

--
thanks,
john h