KVM: Don't shrink/grow vCPU halt_poll_ns if host side polling is disabled

Don't waste cycles to shrink/grow vCPU halt_poll_ns if host
side polling is disabled.
Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

virt/kvm/kvm_main.c

@@ -2360,9 +2360,10 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 	kvm_arch_vcpu_unblocking(vcpu);
 	block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
 
-	if (!vcpu_valid_wakeup(vcpu))
+	if (!kvm_arch_no_poll(vcpu)) {
+		if (!vcpu_valid_wakeup(vcpu)) {
 			shrink_halt_poll_ns(vcpu);
-	else if (halt_poll_ns) {
+		} else if (halt_poll_ns) {
 			if (block_ns <= vcpu->halt_poll_ns)
 				;
 			/* we had a long block, shrink polling */
@@ -2372,8 +2373,10 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 			else if (vcpu->halt_poll_ns < halt_poll_ns &&
 				block_ns < halt_poll_ns)
 				grow_halt_poll_ns(vcpu);
-	} else
+		} else {
 			vcpu->halt_poll_ns = 0;
+		}
+	}
 
 	trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu));
 	kvm_arch_vcpu_block_finish(vcpu);