[PATCH v6 08/12] KVM: nSVM: Disable LBRV in nested control cache when unsupported

[Sean Christopherson]

From: Shivansh Dhiman <shivansh.dhiman@xxxxxxx>

Clear SVM_MISC2_ENABLE_V_LBR in __nested_copy_vmcb_control_to_cache() when
the vCPU does not support LBR Virtualization. This lets the cached value be
consumed directly instead of re-checking X86_FEATURE_LBRV on every access.

Suggested-by: Yosry Ahmed <yosry@xxxxxxxxxx>
Signed-off-by: Shivansh Dhiman <shivansh.dhiman@xxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 arch/x86/kvm/svm/nested.c | 8 +++++---
 arch/x86/kvm/svm/svm.c    | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index b61149814acc..aca2bbc66f47 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -527,12 +527,16 @@ void __nested_copy_vmcb_control_to_cache(struct kvm_vcpu *vcpu,
 
 	/* Always clear misc_ctl bits that the guest cannot use */
 	to->misc_ctl = from->misc_ctl;
+	to->misc_ctl2 = from->misc_ctl2;
 	if (!guest_cpu_cap_has(vcpu, X86_FEATURE_NPT))
 		to->misc_ctl &= ~SVM_MISC_ENABLE_NP;
 
 	if (!gmet_enabled || !guest_cpu_cap_has(vcpu, X86_FEATURE_GMET))
 		to->misc_ctl &= ~SVM_MISC_ENABLE_GMET;
 
+	if (!guest_cpu_cap_has(vcpu, X86_FEATURE_LBRV))
+		to->misc_ctl2 &= ~SVM_MISC2_ENABLE_V_LBR;
+
 	to->iopm_base_pa        = from->iopm_base_pa & PAGE_MASK;
 	to->msrpm_base_pa       = from->msrpm_base_pa & PAGE_MASK;
 	to->tsc_offset          = from->tsc_offset;
@@ -550,7 +554,6 @@ void __nested_copy_vmcb_control_to_cache(struct kvm_vcpu *vcpu,
 	to->event_inj_err       = from->event_inj_err;
 	to->next_rip            = from->next_rip;
 	to->nested_cr3          = from->nested_cr3;
-	to->misc_ctl2		= from->misc_ctl2;
 	to->pause_filter_count  = from->pause_filter_count;
 	to->pause_filter_thresh = from->pause_filter_thresh;
 
@@ -737,8 +740,7 @@ static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3,
 
 static bool nested_vmcb12_has_lbrv(struct kvm_vcpu *vcpu)
 {
-	return guest_cpu_cap_has(vcpu, X86_FEATURE_LBRV) &&
-		(to_svm(vcpu)->nested.ctl.misc_ctl2 & SVM_MISC2_ENABLE_V_LBR);
+	return to_svm(vcpu)->nested.ctl.misc_ctl2 & SVM_MISC2_ENABLE_V_LBR;
 }
 
 static void nested_vmcb02_prepare_save(struct vcpu_svm *svm)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 775eccfb7b24..5253c0143666 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -882,7 +882,7 @@ static bool svm_need_lbr_virtualization(struct kvm_vcpu *vcpu)
 	if (svm->vmcb->save.dbgctl & DEBUGCTLMSR_LBR)
 		return true;
 
-	return is_guest_mode(vcpu) && guest_cpu_cap_has(vcpu, X86_FEATURE_LBRV) &&
+	return is_guest_mode(vcpu) &&
 	       (svm->nested.ctl.misc_ctl2 & SVM_MISC2_ENABLE_V_LBR);
 }
 
-- 
2.56.0.rc1.315.gc6ed9934b7-goog