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SubjectRe: Why such a big difference in init-time PCI resource call-paths (x86 vs x86_64) ?
Yinghai Lu wrote:
> On Thu, May 1, 2008 at 1:11 PM, Andi Kleen <andi@firstfloor.org> wrote:
>> On Thu, May 01, 2008 at 11:16:31AM -0700, Jesse Barnes wrote:
>> > On Wednesday, April 30, 2008 9:07 am TJ wrote:
>> > > In preparation for writing a Windows-style PCI resource allocation
>> > > strategy
>> > >
>> > > - use all e820 gaps for IOMEM resources; top-down allocation -
>> > >
>> > > and thus giving devices with large IOMEM requirements more chance of
>> > > allocation in the 32-bit address space below 4GB (see bugzilla #10461),
>>
>> I tried that some time ago and it turned out that some systems have
>> mappings in holes and don't boot anymore when you fill the holes too much.
>> But that was only considering e820. if you do this it might work if you
>> do it really like windows and consider all resources, including ACPI.
>
> wonder if using holes in MTRR AND e820 could help...
>

Typically not, since the MTRRs won't tell you what is free address space
and what is occupied by non-BAR I/O devices.

-hpa


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