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Date: Fri, 13 Mar 2009 09:44:02 +0100
Message-ID: <2d05c4580903130144t8e92950l7a6cb1078a8a577b@mail.gmail.com>
Subject: Linux* Processor Microcode Data File
From: Dragoslav Zaric <dragoslav.zaric.kd@gmail.com>
To: LKML <linux-kernel@vger.kernel.org>
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---------------------------------------------
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)."
---------------------------------------------

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.


-- 
Thanks

Dragoslav Zaric
[Programmer ; M.Sc. in Astrophysics]
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