[PATCH v10 3/4] powerpc/powernv: Override pcibios_default_alignment() to force PCI devices to be page aligned

[Bjorn Helgaas]

On Sat, Apr 15, 2017 at 5:06 PM, Benjamin Herrenschmidt
<benh at kernel.crashing.org> wrote:
> On Sat, 2017-04-15 at 11:36 -0500, Bjorn Helgaas wrote:
>> > I agree in principle. I'm surprised that PowerPC is the only one
>> > interested here though, what about other platforms who want to use
>> > KVM and PCI pass-through and use Linux to assign BARs ?
>>
>> If I understand correctly, the problem is with BARs smaller than a
>> page, and this happens more on PowerPC because larger page sizes are
>> more common there.
>
> Yes, it happens "more". That doesn't mean it doesn't happen at all on
> others :-) Anyway, I'm not objecting, just surprised.

Yeah, I agree.  Maybe the devices interesting for pass-through tend to
have BARs of least 4KB?  Those would never be a problem on x86.  But I
have absolutely no data either way.