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Instead, ignore writes to GUEST_TSC_FREQ, >>> similar to MSR_IA32_TSC, and log a warning instead. >> >> Why? >> >> Nothing should poke at the TSC MSR and those who do, deserve what they get. >> >>> Only terminate the guest when reading from intercepted GUEST_TSC_FREQ MSR >>> with Secure TSC enabled, as this indicates an unexpected hypervisor >>> configuration. >> >> Huh, this sounds weird. >> >> What are we "fixing" here? > > Returning ES_VMM_ERROR is misleading/wrong, and panicking doesn't match how the > kernel handles every other "bad" WRMSR. How's this for a changelog? > > For Secure TSC enabled guests, don't panic if the kernel hits a #VC due > to attempting to write to GUEST_TSC_FREQ, and instead WARN and drop the > write. The kernel should never write GUEST_TSC_FREQ as it's read-only, > but panicking with ES_VMM_ERROR is both misleading (it's entirely > reasonable for a VMM to intercept writes to a read-only MSR), and > unnecessary, e.g. the kernel eats #GPs with a WARN on every other "bad" > WRMSR. Maybe it should be returning ES_EXCEPTION then instead of ES_VMM_ERROR and forward a #GP, which is what would have happened if the guest tried to write to the read-only MSR if it wasn't being intercepted. I'm still not a fan of intercepting writes to read-only MSRs that are passed into the guest. If we're trying to replicate bare-metal behavior, then allowing the write to fail with a #GP seems appropriate. Thanks, Tom