RE: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

[Thomas Gleixner]

On Wed, 10 Jan 2018, Van De Ven, Arjan wrote:
> > In other words, if you use late microcode loading for getting IBRS, you
> > don't get ALTERNATIVE patching and its benefits?
> > 
> > I'll also profess some microcode ignorance here.  Is "late microcode
> > patching" *all* of the stuff we do from the OS, or do we have early and
> > late Linux loading in addition to what the BIOS can do?
> 
> the early boot loader level stuff is much better generally (but does not
> work when the microcode comes out after the system booted... like really
> long uptimes)

That stuff indeed would be way simpler w/o the late support, but the fact
that the microcode for this might reach the user way later than the kernel
support makes it almost a must to support the late loading.

Thanks,

	tglx