KVM: VMX: Don't invalidate hv_tlb_eptp if the new EPTP matches

Don't invalidate the common EPTP, and thus trigger rechecking of EPTPs
across all vCPUs, if the new EPTP matches the old/common EPTP.  In all
likelihood this is a meaningless optimization, but there are (uncommon)
scenarios where KVM can reload the same EPTP.
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210305183123.3978098-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -3117,7 +3117,8 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa,
 		if (kvm_x86_ops.tlb_remote_flush) {
 			spin_lock(&to_kvm_vmx(kvm)->ept_pointer_lock);
 			to_vmx(vcpu)->ept_pointer = eptp;
-			to_kvm_vmx(kvm)->hv_tlb_eptp = INVALID_PAGE;
+			if (eptp != to_kvm_vmx(kvm)->hv_tlb_eptp)
+				to_kvm_vmx(kvm)->hv_tlb_eptp = INVALID_PAGE;
 			spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
 		}