Re: [PATCH] x86/tdx: Mark TSC reliable

[Kirill A. Shutemov]

On Thu, Aug 24, 2023 at 05:49:05PM +0200, Thomas Gleixner wrote:
> On Tue, Aug 08 2023 at 23:01, Kirill A. Shutemov wrote:
> > On Tue, Aug 08, 2023 at 10:13:05AM -0700, Dave Hansen wrote:
> >> I take it this is carved in stone in the TDX specs somewhere.  A
> >> reference would be nice.
> >
> > TDX Module 1.0 spec:
> >
> > 	5.3.5. Time Stamp Counter (TSC)
> >
> > 	TDX provides a trusted virtual TSC to the guest TDs. TSC value is
> > 	monotonously incrementing, starting from 0 on TD initialization by the
> > 	host VMM. The deviation between virtual TSC values read by each VCPU is
> > 	small.
> 
> Nice weasel wording. What's the definition of "small"?

The newer spec says "Virtual TSC values are consistent among all the TD’s
VCPUs at the level supported by the CPU".

-- 
  Kiryl Shutsemau / Kirill A. Shutemov