linux-kernel - Re: Testing RAM from userspace / question about memmap= arguments

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Message-ID: <20071223111752.GA2340@elf.ucw.cz>
Date:	Sun, 23 Dec 2007 12:17:52 +0100
From:	Pavel Machek <pavel@....cz>
To:	David Newall <david@...idnewall.com>
Cc:	Richard D <richard@...unus.com>,
	'Matthew Bloch' <matthew@...emark.co.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: Testing RAM from userspace / question about memmap= arguments

On Sun 2007-12-23 18:05:59, David Newall wrote:
> Pavel Machek wrote:
>> On Sun 2007-12-23 07:06:58, David Newall wrote:
>>   
>>> It's kind of hard to run anything over SSH if it has to be run before 
>>> userspace is up.  But the kernel can collect results from a modified 
>>> memtest, after it chains back.
>>>     
>>
>> memtest can be ran from userspace, that's the point.
>>   
>
> I'm not sure I believe that.  You need to tinker with hardware tables 
> before you know what physical RAM is being used.  Sequential virtual

No, I can just use /dev/mem. (After passing mem=XXX exactmap to kernel
so that I know what I may play with).

>> Yes, that's what CPU microcode update is for. And I want to test my
>> RAM with up-to-date microcode.
>>   
>
> Don't microcode updates fix CPU bugs?  That's not fixing faulty RAM.

L1/L2 cache is part of memory subsystem.

> I suppose a CPU retains microcode updates, once loaded, until power-down or 
> some hard reboot that you surely can avoid.  If it does happen that
> you

If CPU retains microcode after reset, then you are right. I'm not
sure.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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