Re: [PATCH] dracut: add support for updating the CPU microcode

["Alexander E. Patrakov" <patrakov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

16.04.2016 18:54, Guido Trentalancia пишет:
> Hello Andrei,
>
> thanks for getting back on this...
>
> On Sat, 16/04/2016 at 09.01 +0300, Andrei Borzenkov wrote:
>> 16.04.2016 02:18, Guido Trentalancia пишет:
>>> This is the initial version of a new "microcode" dracut module
>>> that can be used to update the microcode on Intel(R) CPUs.
>>>
>>
>> ??? dracut already supports early microcode loading, why it is not
>> enough and what problem this patch solves?
>
> To be honest, I didn't notice it. I was expecting such support, if
> available, to be a module and I couldn't find it, so I wrote it.
>
> However, I have noticed it is much simpler than the actual
> implementation. It doesn't differentiate between Intel and AMD (why it
> should ?), it just loads the microcode in the standard location as
> defined by the microcode update utility.

The microcode update utility stopped working when a Haswell microcode 
update got released that makes some CPU instructions illegal (because 
they didn't work properly in the first place). Please see 
http://bugs.debian.org/762195

Sure, glibc no longer uses these instructions, but now (exactly to avoid 
repetition of this bug) the only supported way to update the microcode 
is to place it in the initcpio so that "early microcode update" in the 
kernel loader notices it.

-- 
Alexander E. Patrakov