Re: [PATCH RFC] x86: check for and defend against BIOS memory corruption

From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Kasper Sandberg <lkml@metanurb.dk>
Cc: "Yinghai Lu" <yhlu.kernel@gmail.com>,
	"Ingo Molnar" <mingo@elte.hu>, "Rafa? Mi?ecki" <zajec5@gmail.com>,
	"Alan Jenkins" <alan-jenkins@tuffmail.co.uk>,
	"Hugh Dickens" <hugh@veritas.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC] x86: check for and defend against BIOS memory	corruption
Date: Fri, 29 Aug 2008 18:15:31 -0700	[thread overview]
Message-ID: <48B89F33.30507@goop.org> (raw)
In-Reply-To: <1220041877.9776.26.camel@localhost>

Kasper Sandberg wrote:
> On Thu, 2008-08-28 at 20:28 -0700, Jeremy Fitzhardinge wrote:
>   
>> Yinghai Lu wrote:
>>     
>>> On Thu, Aug 28, 2008 at 12:52 PM, Jeremy Fitzhardinge <jeremy@goop.org> wrote:
>>>       
> <snip>
>   
>> Yeah, OK, but I think it should default to ON for now.  The problem is
>> that we had two very different systems (Sony Vaio and Intel desktop)
>> exhibit the same problem in two different ways.  These systems worked
>>     
>
> This is very interresting. I have a gigabyte X48 board, and everything
> works perfect, however, in memtest86+ i get thousands of errors in the
> range 0-0.9mb. I am certain my ram is fine, i've tried it in other
> computers, and reversed. I've run dozens of stress tests within my
> booted linux, no trouble, also the userspace memtester (allthough im
> aware it wont actually ever get to grab offending addresses).
>
> Any thoughts?
>   

I would expect you'd get crashes if you had massive corruption in that
area.  By default it's being used for the kernel pagetables, so stomping
on them will cause problems.  In the cases we've been looking at so far,
it's only been a word or two being stomped.

The low 1Mbyte is used as general memory, so corruption over the whole
area will have widespread effects.

But try this patch (Hugh's version) and see what happens.

    J