Re: x86, microcode: BUG: microcode update that changes x86_capability

From: Josh Boyer
Date: Fri Sep 19 2014 - 09:14:55 EST

On Fri, Sep 19, 2014 at 8:54 AM, Chuck Ebbert <cebbert.lkml@xxxxxxxxx> wrote:
> On Fri, 19 Sep 2014 13:29:53 +0200
> Borislav Petkov <bp@xxxxxxxxx> wrote:
>> On Fri, Sep 19, 2014 at 08:00:15AM -0300, Henrique de Moraes Holschuh wrote:
>> > We're also killing microcode update support outside of the initramfs in
>> > Debian. It has become obvious that anything other than the early initramfs
>> > method of microcode updates should be considered a developer thing.
>> That's simply not true: long-running systems which you can't reboot for
>> whatever reason will need the late microcode update.
> Assuming we can identify all the affected models and steppings, maybe
> something like this would work:
> 1) Refuse to finish booting if a microcode update that disables TSX
> isn't applied before userspace starts running on those CPUs.

How would you accomplish that when applying a microcode update
requires userspace? Or did you mean "before we transition out of the

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