On Tue, 2014-04-08 at 10:53 +0800, Fengguang Wu wrote: > Hi Benjamin, > > > Fengguang, > > > > I ran your script against freshly-checked-out source from staging-next, and > > was not able to reproduce the error with it. My boot log is attached. I > > noticed that your log did not have "Hypervisor detected: KVM" in the trace. > > The KVM options in your script also differ substantially from the ones > > shown at the end of your trace... > > > When I reran your script with the "-cpu Haswell,+smep,+smap" option I was > > able to get the same result as you. IMHO KVM should not be setting this bit > > if it's emulating bare metal. > > Sorry.. We tried to provide a simplified reproduce script and in your > case, it has a significant mismatch with the real KVM options. We'll > fix it, thanks for pointing it out! > > Thanks, > Fengguang
That will be helpful, and as I mentioned, I can reproduce your results, but I'm still not sure why a virtualized processor is giving an invalid opcode fault on a vmcall. The Intel documentation is pretty specific about this - IF not in VMX operation THEN #UD; ELSIF in VMX non-root operation THEN VM exit. Either KVM should be saying "I'm a real processor and not a virtual CPU, really!" - in which case, the hypervisor bit should be off and vmcalls should cause an invalid opcode fault, or, KVM should be saying "I'm a vritualized processor!" and setting the hypervisor bit, and doing a vmexit on vmcall instead. This seems like a KVM bug to me. -- Ben
