On Wed, Jan 10, 2018 at 07:20:13AM +0100, Ingo Molnar wrote:
> it be really unreasonable to say that if a microcode update changes CPU
> flags an initrd rebuild and a reboot is required? It's not like microcode
> updates
> are _that_ frequent - in fact they tend to be much _less_ frequent in a
> system's
> life time than kernel updates.
>
> So all of this 'late loading' and CPU flag splitting complexity seems
> unnecessary
> to me: we should be glad we do early microcode loading now, and should
> embrace it.
>
> Changing CPU features way after the CPU has booted up is possible, and we
> could in
> theory extend code patching to work 'late' as well, but given how infrequent
> all
> this is bound to be in practice I fear it's all going to be a big, seldom
> tested,
> often broken mess, with no real benefit to users.
Agreed: we support that late patching for those use cases where machines
run for a long time, simulating all kinds of crap. And frankly, if
those things need to get IBRS all of a sudden and *not* reboot, then
something's wrong with the whole contraption setup.
So yes, I'd vote too for supporting only early IBRS and not do the late
thing now. Maybe later, if there's, like, a really compelling use case.
I will have to do the late thing for our old kernels which don't have
early loading but that would be a one-off and my problem.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
