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    SubjectRe: [visorchipset] invalid opcode: 0000 [#1] PREEMPT SMP
    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
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