KVM: x86: nSVM: optimize svm_set_x2apic_msr_interception

- Avoid toggling the x2apic msr interception if it is already up to date.

- Avoid touching L0 msr bitmap when AVIC is inhibited on entry to
  the guest mode, because in this case the guest usually uses its
  own msr bitmap.

  Later on VM exit, the 1st optimization will allow KVM to skip
  touching the L0 msr bitmap as well.

Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20220519102709.24125-18-suravee.suthikulpanit@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index bb0457c1e41c..37ce061dfc76 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -809,6 +809,9 @@ void svm_set_x2apic_msr_interception(struct vcpu_svm *svm, bool intercept)
 {
 	int i;
 
+	if (intercept == svm->x2avic_msrs_intercepted)
+		return;
+
 	if (avic_mode != AVIC_MODE_X2 ||
 	    !apic_x2apic_mode(svm->vcpu.arch.apic))
 		return;
@@ -822,6 +825,8 @@ void svm_set_x2apic_msr_interception(struct vcpu_svm *svm, bool intercept)
 		set_msr_interception(&svm->vcpu, svm->msrpm, index,
 				     !intercept, !intercept);
 	}
+
+	svm->x2avic_msrs_intercepted = intercept;
 }
 
 void svm_vcpu_free_msrpm(u32 *msrpm)
@@ -1393,6 +1398,8 @@ static int svm_vcpu_create(struct kvm_vcpu *vcpu)
 		goto error_free_vmsa_page;
 	}
 
+	svm->x2avic_msrs_intercepted = true;
+
 	svm->vmcb01.ptr = page_address(vmcb01_page);
 	svm->vmcb01.pa = __sme_set(page_to_pfn(vmcb01_page) << PAGE_SHIFT);
 	svm_switch_vmcb(svm, &svm->vmcb01);