linux-kernel - Re: Intel's response Linux/MTRR/8GB Memory Support / Why doesn't the kernel realize the BIOS has problems and re-map appropriately?

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Message-ID: <4662869A.9030700@gmail.com>
Date:	Sun, 03 Jun 2007 10:15:06 +0100
From:	Matt Keenan <tank.en.mate@...il.com>
To:	Justin Piszcz <jpiszcz@...idpixels.com>
CC:	Andi Kleen <andi@...stfloor.org>,
	Venki Pallipadi <venkatesh.pallipadi@...el.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	linux-kernel@...r.kernel.org
Subject: Re: Intel's response Linux/MTRR/8GB Memory Support / Why doesn't
 the kernel realize the BIOS has problems and re-map appropriately?

Justin Piszcz wrote:
>
>
> On Sat, 2 Jun 2007, Andi Kleen wrote:
>
>>> I feel, having a silent/transparent workaround is not a good idea.
>>> With that
>>
>> If enough RAM is chopped off users will notice. They tend to complain
>> when they miss RAM.  I don't like panic very much because for many
>> users it will be a show stopper (even when they are not blessed
>> with "quiet" boots like some distributions do)
>>
>> The message in dmesg could be also emphasized a bit with a little
>> ASCII art (but no <blink> tag in there)
>>
>> The problem I'm more worried about is if the system will be really
>> stable --- could it be that the memory controller is still
>> misconfigured and cause other stability issues? (we've had such
>> cases in the past). Also I'm not sure we can handle the case of
>> the MTRR wrong not at the end of memory but at the hole sanely.
>>
>> -Andi
>>
>
> So far I have been booting with mem=8832M and have run stress/loaded
> the memory subsystem pretty good; what other tests should I run?
>
> It'd be nice if we could pose some sort of solution/warning for the
> future so other people do not have to experience the same problems.
>
> What are the next steps?
>
Wouldn't it be possible for the e820/MTRR set up code detect the problem
and suggest a mem=xxxx that would fix the problem (while also
complaining that the BIOS is broken)?

Matt

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