[7/8,nVMX] : Enable "load IA32_PERF_GLOBAL_CTRL VM-{entry,exit} controls
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Message ID 20190424231724.2014-8-krish.sadhukhan@oracle.com
State New
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Series
  • [1/8,KVMnVMX] : Enable "load IA32_PERF_GLOBAL_CTRL" VM-exit control for nested guests
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Commit Message

Krish Sadhukhan April 24, 2019, 11:17 p.m. UTC
...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(+)

Comments

Sean Christopherson May 13, 2019, 7:12 p.m. UTC | #1
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
>
Jim Mattson Aug. 15, 2019, 11:02 p.m. UTC | #2
On Mon, May 13, 2019 at 12:12 PM Sean Christopherson
<sean.j.christopherson@intel.com> 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@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.

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!

Patch
diff mbox series

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);
 
 	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)