Re: Why such a big difference in init-time PCI resource call-paths(x86 vs x86_64) ?

[H. Peter Anvin]

Yinghai Lu wrote:
> On Thu, May 1, 2008 at 1:11 PM, Andi Kleen <andi@xxxxxxxxxxxxxx> 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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