On Wed, Sep 02, 2020 at 06:45:38PM +0200, [email protected] wrote:
> We really should clear the CPUID bits when the kernel explicitly
> disables things.
Actually, you want to *disable* the functionality behind it by clearing
a bit in CR4 - and yes, not all features have CR4 bits - so that
luserspace doesn't "probe" the existence of certain instructions.
Example: you can still try to run RDRAND and succeed even if the
corresponding CPUID bit is clear.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
