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It reads like arbitrary KVM behavior. And >>> IMO the most notable thing is what's missing: an intercept check. _That_ is >>> worth commenting, e.g. >>> >>> /* >>> * VMMCALL #UDs if it's not intercepted, and KVM reaches this point if >>> * and only if the VMCALL intercept is not set in vmcb12. >>> */ >> Not intercepting VMMCALL is stated to be an unconditional VMRUN >> failure.  APM Vol3 15.5 Canonicalization and Consistency Checks. > Hrm, I can't find that. I see: > > The VMRUN intercept bit is clear. > > but I don't see anything about VMMCALL being a mandatory intercept. Gah.  I even double checked before sending, but I'm apparently completely blind to the difference between VMRUN and VMMCALL. Sorry for the noise. ~Andrew