Re: [PATCH v4 09/25] KVM: VMX: nVMX: Support TSC scaling and PERF_GLOBAL_CTRL with enlightened VMCS

Sean Christopherson
2022-07-25T18:18:53Z

On Mon, Jul 25, 2022, Paolo Bonzini wrote:
> On 7/21/22 23:58, Sean Christopherson wrote:
> >
> > diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
> > index b5cfbf7d487b..7b348a03e096 100644
> > --- a/arch/x86/kvm/vmx/evmcs.c
> > +++ b/arch/x86/kvm/vmx/evmcs.c
> > @@ -355,11 +355,6 @@ uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu)
> > return 0;
> > }
> >
> > -enum evmcs_v1_revision {
> > - EVMCSv1_2016,
> > - EVMCSv1_2022,
> > -};
> > -
> > enum evmcs_unsupported_ctrl_type {
> > EVMCS_EXIT_CTLS,
> > EVMCS_ENTRY_CTLS,
> > @@ -372,29 +367,29 @@ static u32 evmcs_get_unsupported_ctls(struct kvm_vcpu *vcpu,
> > enum evmcs_unsupported_ctrl_type ctrl_type)
> > {
> > struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
> > - enum evmcs_v1_revision evmcs_rev = EVMCSv1_2016;
> > + bool has_evmcs_2022_features;
> >
> > if (!hv_vcpu)
> > return 0;
> >
> > - if (hv_vcpu->cpuid_cache.nested_ebx & HV_X64_NESTED_EVMCS1_2022_UPDATE)
> > - evmcs_rev = EVMCSv1_2022;
> > + has_evmcs_2022_features = hv_vcpu->cpuid_cache.nested_ebx &
> > + HV_X64_NESTED_EVMCS1_2022_UPDATE;
> >
> > switch (ctrl_type) {
> > case EVMCS_EXIT_CTLS:
> > - if (evmcs_rev == EVMCSv1_2016)
> > + if (!has_evmcs_2022_features)
> > return EVMCS1_UNSUPPORTED_VMEXIT_CTRL |
> > VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
> > else
> > return EVMCS1_UNSUPPORTED_VMEXIT_CTRL;
> > case EVMCS_ENTRY_CTLS:
> > - if (evmcs_rev == EVMCSv1_2016)
> > + if (!has_evmcs_2022_features)
> > return EVMCS1_UNSUPPORTED_VMENTRY_CTRL |
> > VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
> > else
> > return EVMCS1_UNSUPPORTED_VMENTRY_CTRL;
> > case EVMCS_2NDEXEC:
> > - if (evmcs_rev == EVMCSv1_2016)
> > + if (!has_evmcs_2022_features)
> > return EVMCS1_UNSUPPORTED_2NDEXEC |
> > SECONDARY_EXEC_TSC_SCALING;
> > else
> >
>
> I kind of like the idea of having a two-dimensional array based on the enums
> instead of switch statements, so for now I'll keep Vitaly's enums.

I don't have a strong opinion on using a 2d array, but unless I'm missing something,
that's nowhere to be found in this patch. IMO, having the enums without them
providing any unique value is silly and obfuscates the code.