Re: [tip:x86/setup] x86, setup: "glove box" BIOS calls -- infrastructure

From: "H. Peter Anvin" <hpa@zytor.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Avi Kivity <avi@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Pavel Machek <pavel@ucw.cz>,
	mingo@redhat.com, linux-kernel@vger.kernel.org,
	tglx@linutronix.de, hpa@linux.intel.com, rjw@sisk.pl,
	linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/setup] x86, setup: "glove box" BIOS calls --	infrastructure
Date: Mon, 13 Apr 2009 09:27:20 -0700	[thread overview]
Message-ID: <49E367E8.7080202@zytor.com> (raw)
In-Reply-To: <20090413042459.GA6479@elte.hu>

Ingo Molnar wrote:
>> Yes, we could do memory checks, and ... hey, we already do that:
>>
>>    bb577f9: x86: add periodic corruption check
>>    5394f80: x86: check for and defend against BIOS memory corruption
>>
>> ... and i seem to be the one who implemented it! ;-)
> 
> s/implemented/merged+fixed :-)

Actually, what would probably be more productive than trying to track
corruption would be to drop the low 1 MB of memory before suspend to RAM
- make sure that it is as close to completely unused as possible.

All *known* cases of low memory corruption are either boot time or due
to s2ram.

I don't know how realistic it is to make the low 1 MB completely unused
over the s2ram cycle.  The trivial way of doing it is to simply not use
it -- it's only some 600K after all; a more sophisticated way would be
to explicitly constrain it to transient uses that would be dead at s2ram.

	-hpa

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