Re: [PATCH] x86/entry/64: Disallow RDPID in paranoid entry if KVM is enabled

[Borislav Petkov]

On Fri, Aug 21, 2020 at 11:05:24AM +0200, Paolo Bonzini wrote:
> ... RDTSCP is used as an ordered rdtsc but it discards the TSC_AUX
> value.

... and now because KVM is using it, the kernel can forget using
TSC_AUX. Are you kidding me?!

> Hence the assumption that KVM makes (and has made ever since TSC_AUX was
> introduced.

And *this* is the problem. KVM can't just be grabbing MSRs and claiming
them because it started using them first. You guys need to stop this. If
it is a shared resource, there better be an agreement about sharing it.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette