Re: [PATCH v2 1/3] KVM: x86: implement KVM_{GET|SET}_TSC_STATE

[Thomas Gleixner]

On Tue, Dec 08 2020 at 09:33, Andy Lutomirski wrote:
> On Tue, Dec 8, 2020 at 8:26 AM Maxim Levitsky <mlevitsk@xxxxxxxxxx> wrote:
>
> IIRC we introduced mul_u64_u32_shift() for roughly this reason,but we
> don't seem to be using it in the relevant code paths.  We should be
> able to use the same basic math with wider intermediates to allow very
> large intervals between updates.

That's 128 bit math and _NO_ we are not going there for various
reasons.

Hint1: There is a world outside of x8664 and TSC.
Hint2: Even on x8664 and TSC it comes with performance overhead

Thanks,

        tglx