Re: [PATCH 5/5] PNP: HP nx6325 fixup: reserve unreported resources

H. Peter Anvin
2010-12-15T18:27:50Z

On 12/15/2010 10:18 AM, Bjorn Helgaas wrote:
>
> ACPI devices tend to be at high addresses, so allocating top-down
> is definitely more dangerous unless we explicitly avoid them. I
> should have realized that and done something like patches 1-3 of
> this series before the top-down patches.
>
> Doing it bottom-up would very likely work better than the "top-down
> without avoiding ACPI regions" model we currently have, at least in
> the short term. We *would* have to do something to avoid E820
> reservations to fix this:
> https://bugzilla.kernel.org/show_bug.cgi?id=16228,
> but that's doable.
>
> So here's my proposal for .37:
> - Keep the current state of _CRS enabled by default (for 2008
> and newer machines).
> - Allocate bottom-up always
> - Avoid E820 reservations
>
> That should fix all the regressions I'm aware of. I'll work on
> the patches this afternoon.
>

At the same time, I would like to see a few things done as a matter of
course:

a) reserve the top 2 MiB of the 32-bit address space. There *will* be
ROM at the top of the 32-bit address space; it's a fact of the
architecture, and on at least older systems it was common to have a
shadow 1 MiB below.

b) we may want to consider doing special things in the 0xFExxxxxx memory
range, which is used by the CPU-APIC-MSI system in recent processors.

-hpa

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