On Thu, Aug 20, 2020 at 6:34 AM Maxim Levitsky <mlevitsk@xxxxxxxxxx> wrote: > > This will be used later to return an error when setting this msr fails. > > For VMX, it already has an error condition when EFER is > not in the shared MSR list, so return an error in this case. > > Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx> > --- > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1471,7 +1471,8 @@ static int set_efer(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > efer &= ~EFER_LMA; > efer |= vcpu->arch.efer & EFER_LMA; > > - kvm_x86_ops.set_efer(vcpu, efer); > + if (kvm_x86_ops.set_efer(vcpu, efer)) > + return 1; This seems like a userspace ABI change to me. Previously, it looks like userspace could always use KVM_SET_MSRS to set MSR_EFER to 0 or EFER_SCE, and it would always succeed. Now, it looks like it will fail on CPUs that don't support EFER in hardware. (Perhaps it should fail, but it didn't before, AFAICT.)
