linux-kernel - Re: [PATCH] x86: make sure wakeup code is below 1M -v2

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Date:	Fri, 13 Nov 2009 08:36:08 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Pavel Machek <pavel@....cz>, Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Len Brown <lenb@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH] x86: make sure wakeup code is below 1M -v2


* Rafael J. Wysocki <rjw@...k.pl> wrote:

> On Thursday 12 November 2009, Pavel Machek wrote:
> > On Tue 2009-11-10 18:27:23, Yinghai Lu wrote:
> > > 
> > > try to find_e820_area/reserve_early, and call acpi_reserve_memory early
> > > 
> > > to get area is below 1M
> > 
> > Does it fix anything? I can't tell from the changelog...
> 
> Yes, it does.  If the area is above 1M, we can't run real mode code 
> from it.
> 
> This matters for NUMA machines supporting S3 (yes, there are a few 
> models out there).

It might also matter in more exotic kernels that might do some large 
allocations. (say 'nopentium' can cause +1MB/+2MB of kernel page table 
allocations per one GB of RAM)

Physical constraints to allocations (which this is) should be expressed 
early and with high priority, to make sure they can be met.

	Ingo
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