On Fri, 5 Aug 2022 13:42:40 +0200, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > On 8/3/22 20:21, Sean Christopherson wrote: > >> I've noticed test_illegal_movbe() does not execute with KVM_FEP. > >> Just making sure: is it intentional? > > It's intentional. FEP isn't needed because KVM emulates MOVBE on #UD when it's > > not supported by the host, e.g. to allow migrating to an older host. > > > > GP(EmulateOnUD | ModRM, &three_byte_0f_38_f0), > > GP(EmulateOnUD | ModRM, &three_byte_0f_38_f1), > > > > *puts historian hat on* > > The original reason was to test Linux using MOVBE even on non-Atom > machines, when MOVBE was only on Atoms. :) So the emulator's logic for MOVBE is meant to be tested only when the guest supports MOVBE while the host does not? Michal
