linux-kernel - Re: Linux* Processor Microcode Data File

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Date:	Fri, 13 Mar 2009 10:55:44 -0400
From:	Gene Heskett <gene.heskett@...izon.net>
To:	Dragoslav Zaric <dragoslav.zaric.kd@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Linux* Processor Microcode Data File

On Friday 13 March 2009, Dragoslav Zaric wrote:
>---------------------------------------------
>I found this on web site http://kerneltrap.org
>
>Tigran Aivazian, author of the IA32 microcode driver and Microcode
>Update Utility for Linux explained:
>
>"The answer to your question is that some Intel CPUs (just like any
>other hardware or software) contain bugs
>and, fortunately, their architecture is flexible enough to provide a
>way to fix those bugs by means of loading the
>microcode update on the fly, i.e. while the OS is running with no need
>to reboot (in fact, rebooting or otherwise
>resetting the CPU causes the update to be lost and requires to run the
>update again)."

And what runs this update?  I saw it apply once in the dmesg output, about 3 
full powerdown reboots ago, never since, and the code is still there in 
/lib/firmware

AMD quad core 9550 here, stepping 03.

Thanks.
>---------------------------------------------
>
>So when you reboot system, you reset CPU to original state, and after
>that you must apply microcode, and this
>is what is actually doing right now, you put microcode in folder
>/etc/firmware and after boot microcode is loaded.
>
>So I think for CPU hotplug it is also natural that microcode is loaded
>after plugging, because you can not use
>microcode from boot process. Maybe kernel should have database of
>tested microcodes, so when you plug CPU
>appropriate microcode is loaded.


-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
The only thing that experience teaches us is that experience teaches us 
nothing.
		-- Andre Maurois (Emile Herzog)

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