Re: [PATCH 7/8][KVM nVMX]: Enable "load IA32_PERF_GLOBAL_CTRL VM-{entry,exit} controls

[Sean Christopherson <sean.j.christopherson@intel.com>]

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@oracle.com>
> Suggested-by: Jim Mattson <jmattson@google.com>
> Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
> ---
>  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.

In general, it's difficult for me to understand exactly what functionality
you intend to introduce.  Proper changelogs would be very helpful.

>  
>  	if (kvm_mpx_supported()) {
>  		bool mpx_enabled = guest_cpuid_has(vcpu, X86_FEATURE_MPX);
> @@ -6976,6 +6977,17 @@ static void nested_vmx_entry_exit_ctls_update(struct kvm_vcpu *vcpu)
>  			vmx->nested.msrs.exit_ctls_high &= ~VM_EXIT_CLEAR_BNDCFGS;
>  		}
>  	}
> +	if (pmu_enabled) {
> +		vmx->nested.msrs.entry_ctls_high |=
> +		    VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
> +		vmx->nested.msrs.exit_ctls_high |=
> +		    VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
> +	} else {
> +		vmx->nested.msrs.entry_ctls_high &=
> +		    ~VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL;
> +		vmx->nested.msrs.exit_ctls_high &=
> +		    ~VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL;
> +	}
>  }
>  
>  static void update_intel_pt_cfg(struct kvm_vcpu *vcpu)
> -- 
> 2.17.2
>