[rfc-patch, bugfix] x86-microcode

[Dmitry Adamushko <dmitry.adamushko@gmail.com>]

Hi,


[ consider it a pre-release and RFC... I'm a bit in hurry now and just send what I have got by this moment.
Although, I expect it to be workable ]


this change is supposed to fix bug#11197 (note, its name "Oops in microcode sysfs registration" is misleading)

The problem description can be found here:
http://www.ussg.iu.edu/hypermail/linux/kernel/0807.3/3791.html
or
http://lkml.org/lkml/2008/7/24/260

perhaps it does look quite bulky for -rc, although it's mainly move-redesign-some-bits of the code and
I tried to preserve the original logic (even if it looked like a possible optimizations might had been applied)
as much as possible.

The basic idea is that we introduce another mechanism to run ucode-updates on a target cpu
and replace set_cpus_allowed_ptr() in (1) cpu-hotplug events and (2) module load.


[1/2] x86-microcode: generic updates

Basically, it introduces microcode_update_cpu() which can be run either from start_secondary()
(perhaps via a function pointer) or scheduled via keventd ([2/2]) and reworks the logic of cpu-hotplug events.

[2/2] x86-microcode: do updates via workqueue


More testing is necessary. I tested without ucode-package (so only generic machinery) and for
- load/unload module;
- cpu-hotplug (so it doesn't give an oops anymore)

hm, suspend/resume seems to be broken even without the 'microcode' module (will check the date of my previous kernel).


--Dmitry