On Mon, May 13, 2019 at 12:12 PM Sean Christopherson
<sean.j.christopherson@xxxxxxxxx> wrote:
>
> On Wed, Apr 24, 2019 at 07:17:23PM -0400, Krish Sadhukhan wrote:
> > ...based on whether the guest CPU supports PMU
> >
> > Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
> > Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx>
> > Reviewed-by: Karl Heubaum <karl.heubaum@xxxxxxxxxx>
> > ---
> > arch/x86/kvm/vmx/vmx.c | 12 ++++++++++++
> > 1 file changed, 12 insertions(+)
> >
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index 4d39f731bc33..fa9c786afcfa 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -6964,6 +6964,7 @@ static void nested_vmx_cr_fixed1_bits_update(struct kvm_vcpu *vcpu)
> > static void nested_vmx_entry_exit_ctls_update(struct kvm_vcpu *vcpu)
> > {
> > struct vcpu_vmx *vmx = to_vmx(vcpu);
> > + bool pmu_enabled = guest_cpuid_has_pmu(vcpu);
>
> A revert has been sent for the patch that added guest_cpuid_has_pmu().
>
> Regardless, checking only the guest's CPUID 0xA is not sufficient, e.g.
> at the bare minimum, exposing the controls can be done if and only if
> cpu_has_load_perf_global_ctrl() is true.
I don't think cpu_has_load_perf_global_ctrl() is required. Support for
the VM-entry and VM-exit controls, "load IA32_PERF_GLOBAL_CTRL," can
be completely emulated by kvm, since add_atomic_switch_msr() is
capable of falling back on the VM-entry and VM-exit MSR-load lists if
!cpu_has_load_perf_global_ctrl().
The only requirement should be kvm_pmu_is_valid_msr(MSR_CORE_PERF_GLOBAL_CTRL).
> In general, it's difficult for me to understand exactly what functionality
> you intend to introduce. Proper changelogs would be very helpful.
I concur!
