Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH] x86/tdx: Mark TSC reliable | Date | Fri, 25 Aug 2023 19:09:41 +0200 |
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On Fri, Aug 25 2023 at 16:52, Kirill A. Shutemov wrote: > 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".
That means what? It's not a guarantee for consistency either. :(
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