Re: [PATCH] x86: Construct 32 bit boot time page tables in native format.

H. Peter Anvin
2008-01-25T00:32:23Z

Pavel Machek wrote:
>>>
>> I just looked at the ACPI suspend code, and it looks like it hacks its own
>> identity map at runtime. Pavel, am I reading that code right?
>
> Yes, I think so, I believe we do it on both 32 and 64 bit now.
>

So the background to this... we need an identity map to trampoline at
early boot, obviously, but we'd like it to not stick around more than
necessary. We have zap_low_mappings() now but it's not really sufficient.

Secondary SMP processors need these mappings during trampolining --
presumably including CPU hotplug -- and I'm suspecting it might simply
make sense to use a separate set of page tables (with both the identity
and the kernel map) for trampolining and just keep them around. That
way they would be usable for ACPI as well.

> (It is early here. And I almost got the .c wakeup code to work... it
> already sets the mode).

Sweet!

-hpa