On Thu, Sep 09, 2021 at 05:09:11PM +0000, Sean Christopherson wrote: > On Fri, Sep 10, 2021, Yu Zhang wrote: > > On Thu, Sep 09, 2021 at 07:55:23PM +0800, Hou Wenlong wrote: > > > Per Intel's SDM, use vmcall instruction in non VMX operation for cpl3 > > > it should trigger a #UD. And in VMX root operation, it should > > > > Are you sure? IIRC, vmcall will always cause VM exit as long as CPU > > is in non-root mode(regardless the CPL). > > Correct, VMCALL unconditionally causes VM-Exit in non-root mode, but Hou is > referring to the first fault condition of "non VMX operation". The intent of the > patch is to emulate hardware behavior for CPL>0: if L1 is not in VMX operation, > a.k.a. not post-VMXON, then #UD, else #GP (because VMCALL #GPs at CPL>0 in VMX > root). Oh, I see. It's to make the virtualized world more real. But like you said, it's not KVM's target. And doing that could cause more problems - a PV guest expects the VMCALL to succeed, regardless it has VMX capability or its VMX is on or not. Thanks for the explaination. B.R. Yu
