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

Yinghai Lu
2012-05-29T17:55:28Z

On Fri, May 25, 2012 at 5:12 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> 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;
>    }

x86 are using 16bits.

some others use 32 bits.
#define IO_SPACE_LIMIT 0xffffffff

ia64 and sparc are using 64bits.
#define IO_SPACE_LIMIT 0xffffffffffffffffUL

but pci only support 16bits and 32bits.

maybe later we can add
PCI_MAX_RESOURCE_16

to handle 16bits and 32bit io ports.

Yinghai