Re: [PATCH v3 32/41] x86/tsc: Rejects attempts to override TSC calibration with lesser routine

[David Woodhouse]

On Fri, 2026-05-15 at 12:19 -0700, Sean Christopherson wrote:
> When registering a TSC frequency calibration routine, sanity check that
> the incoming routine is as robust as the outgoing routine, and reject the
> incoming routine if the sanity check fails.
> 
> Because native calibration routines only mark the TSC frequency as known
> and reliable when they actually run, the effective progression of
> capabilities is: None (native) => Known and maybe Reliable (PV) =>
> Known and Reliable (CoCo).  Violating that progression for a PV override
> is relatively benign, but messing up the progression when CoCo is
> involved is more problematic, as it likely means a trusted source of
> information (hardware/firmware) is being discarded in favor of a less
> trusted source (hypervisor).
> 
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

Reviewed-by: David Woodhouse <dwmw@xxxxxxxxxxxx>

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