KVM: VMX: Clean up vmx_flush_tlb_gva()

Refactor vmx_flush_tlb_gva() to remove a superfluous local variable and
clean up its comment, which is oddly located below the code it is
commenting.

No functional change intended.
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200320212833.3507-16-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -2840,15 +2840,11 @@ static void exit_lmode(struct kvm_vcpu *vcpu)
 
 static void vmx_flush_tlb_gva(struct kvm_vcpu *vcpu, gva_t addr)
 {
-	int vpid = to_vmx(vcpu)->vpid;
-
-	vpid_sync_vcpu_addr(vpid, addr);
-
 	/*
-	 * If VPIDs are not supported or enabled, then the above is a no-op.
-	 * But we don't really need a TLB flush in that case anyway, because
-	 * each VM entry/exit includes an implicit flush when VPID is 0.
+	 * vpid_sync_vcpu_addr() is a nop if vmx->vpid==0, see the comment in
+	 * vmx_flush_tlb_guest() for an explanation of why this is ok.
 	 */
+	vpid_sync_vcpu_addr(to_vmx(vcpu)->vpid, addr);
 }
 
 static void vmx_flush_tlb_guest(struct kvm_vcpu *vcpu)