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

H. Peter Anvin
2012-05-30T16:31:12Z

On 05/30/2012 09:27 AM, Bjorn Helgaas wrote:
>
> You're right, the spec does allow the upper 16 bits of I/O BARs to be
> hardwired to zero (PCI spec rev 3.0, p. 226), so this part does make
> some sense. I don't think it applies to x86, since I don't think
> there's a way to generate an I/O access to anything above 64K, but it
> could help other arches.
>
> I'm inclined to be conservative and wait until we find a problem where
> a patch like this would help.
>

The really conservative thing is to just use 16-bit addresses for I/O on
all platforms. I think a lot of non-x86 platforms does that.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.