Re: [PATCH v3 05/27] KVM: VMX: Disable FRED if FRED consistency checks fail

[Xin Li]

On 10/22/2024 1:48 AM, Chao Gao wrote:
> On Mon, Sep 30, 2024 at 10:00:48PM -0700, Xin Li (Intel) wrote:
> > From: Xin Li <xin3.li@xxxxxxxxx>
> >
> > Do not virtualize FRED if FRED consistency checks fail.
> >
> > Either on broken hardware, or when run KVM on top of another hypervisor
> > before the underlying hypervisor implements nested FRED correctly.
> >
> > Suggested-by: Chao Gao <chao.gao@xxxxxxxxx>
> > Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
> > Signed-off-by: Xin Li (Intel) <xin@xxxxxxxxx>
> > Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
>
> Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>
>
> one nit below,
>
> > ---
> > arch/x86/kvm/vmx/capabilities.h | 7 +++++++
> > arch/x86/kvm/vmx/vmx.c          | 3 +++
> > 2 files changed, 10 insertions(+)
> >
> > diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
> > index e8f3ad0f79ee..2962a3bb9747 100644
> > --- a/arch/x86/kvm/vmx/capabilities.h
> > +++ b/arch/x86/kvm/vmx/capabilities.h
> > @@ -400,6 +400,13 @@ static inline bool vmx_pebs_supported(void)
> > 	return boot_cpu_has(X86_FEATURE_PEBS) && kvm_pmu_cap.pebs_ept;
> > }
> >
> > +static inline bool cpu_has_vmx_fred(void)
> > +{
> > +	/* No need to check FRED VM exit controls. */
>
> how about:
>
> 	/*
> 	 * setup_vmcs_config() guarantees FRED VM-entry/exit controls are
> 	 * either all set or none. So, no need to check FRED VM-exit controls.
> 	 */
>
> It is better to call out the reason.

make sense!