On Fri, 2026-05-15 at 12:19 -0700, Sean Christopherson wrote: > If CPUID.0x16 is present and valid, use the CPU frequency provided by > CPUID instead of assuming that the virtual CPU runs at the same > frequency as TSC and/or kvmclock. Back before constant TSCs were a > thing, treating the TSC and CPU frequencies as one and the same was > somewhat reasonable, but now it's nonsensical, especially if the > hypervisor explicitly enumerates the CPU frequency. > > Signed-off-by: Sean Christopherson <[email protected]> > --- > arch/x86/kernel/kvmclock.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index 62c8ea2e6769..7607920ae386 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -190,6 +190,20 @@ void kvmclock_cpu_action(enum kvm_guest_cpu_action > action) > } > } > > +static unsigned long kvm_get_cpu_khz(void) > +{ > + unsigned int cpu_khz; > + > + /* > + * Prefer CPUID over kvmclock when possible, as the base CPU frequency > + * isn't necessarily the same as the kvmlock "TSC" frequency. > + */ > + if (!cpuid_get_cpu_freq(&cpu_khz)) > + return cpu_khz; > + > + return pvclock_tsc_khz(this_cpu_pvti());
I'm fine with this in principle but shouldn't the fallback be calling kvm_get_tsc_khz() instead of directly calling pvclock_tsc_khz()?
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