Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first

Bjorn Helgaas
2012-05-26T00:13:05Z

On Fri, May 25, 2012 at 5:10 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> On Fri, May 25, 2012 at 2:55 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
>> I think we should fix this with a separate patch that removes
>> PCIBIOS_MAX_MEM_32 altogether, replacing this use with an explicit
>> 0xffffffff (or some other "max 32-bit value" symbol).  I don't think
>> there's anything arch-specific about this.
>>
>> So I'd like to see two patches here:
>>  1) Avoid allocating 64-bit regions for 32-bit BARs
>>  2) Try to allocate regions above 4GB for 64-bit BARs
>
> Sure. please check updated two patches.

I think the first one looks good.

I'm curious about the second. Why did you add the IORESOURCE_MEM
test? That's doesn't affect the "start =" piece because
IORESOURCE_MEM is always set if IORESOURCE_MEM_64 is set.

But it does affect the "end =" part. Previously we limited all I/O
and 32-bit mem BARs to the low 4GB. This patch makes it so we limit
32-bit mem BARs to the low 4GB, but we don't limit I/O BARs. But I/O
BARs can only have 32 bits of address, so it seems like we should
limit them the same way as 32-bit mem BARs. So I expected something
like this:

if (res->flags & IORESOURCE_MEM_64) {
start = (resource_size_t) (1ULL << 32);
end = PCI_MAX_RESOURCE;
} else {
start = 0;
end = PCI_MAX_RESOURCE_32;
}