KVM: VMX: Introduce vmx_flush_tlb_current()

Add a helper to flush TLB entries only for the current EPTP/VPID context
and use it for the existing direct invocations of vmx_flush_tlb().  TLB
flushes that are specific to the current vCPU state do not need to flush
other contexts.

Note, both converted call sites happen to be related to the APIC access
page, this is purely coincidental.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200320212833.3507-21-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -2863,6 +2863,22 @@ static void vmx_flush_tlb(struct kvm_vcpu *vcpu)
 	}
 }
 
+static void vmx_flush_tlb_current(struct kvm_vcpu *vcpu)
+{
+	u64 root_hpa = vcpu->arch.mmu->root_hpa;
+
+	/* No flush required if the current context is invalid. */
+	if (!VALID_PAGE(root_hpa))
+		return;
+
+	if (enable_ept)
+		ept_sync_context(construct_eptp(vcpu, root_hpa));
+	else if (!is_guest_mode(vcpu))
+		vpid_sync_context(to_vmx(vcpu)->vpid);
+	else
+		vpid_sync_context(nested_get_vpid02(vcpu));
+}
+
 static void vmx_flush_tlb_gva(struct kvm_vcpu *vcpu, gva_t addr)
 {
 	/*
@@ -6108,7 +6124,7 @@ void vmx_set_virtual_apic_mode(struct kvm_vcpu *vcpu)
 		if (flexpriority_enabled) {
 			sec_exec_control |=
 				SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
-			vmx_flush_tlb(vcpu);
+			vmx_flush_tlb_current(vcpu);
 		}
 		break;
 	case LAPIC_MODE_X2APIC:
@@ -6126,7 +6142,7 @@ static void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu, hpa_t hpa)
 {
 	if (!is_guest_mode(vcpu)) {
 		vmcs_write64(APIC_ACCESS_ADDR, hpa);
-		vmx_flush_tlb(vcpu);
+		vmx_flush_tlb_current(vcpu);
 	}
 }