KVM: Add helpers to wake/query blocking vCPU

Add helpers to wake and query a blocking vCPU.  In addition to providing
nice names, the helpers reduce the probability of KVM neglecting to use
kvm_arch_vcpu_get_wait().

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211009021236.4122790-20-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/arm64/kvm/arch_timer.c

@@ -649,7 +649,6 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
 {
 	struct arch_timer_cpu *timer = vcpu_timer(vcpu);
 	struct timer_map map;
-	struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
 
 	if (unlikely(!timer->enabled))
 		return;
@@ -672,7 +671,7 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
 	if (map.emul_ptimer)
 		soft_timer_cancel(&map.emul_ptimer->hrtimer);
 
-	if (rcuwait_active(wait))
+	if (kvm_vcpu_is_blocking(vcpu))
 		kvm_timer_blocking(vcpu);
 
 	/*

arch/arm64/kvm/arm.c

@@ -631,7 +631,7 @@ void kvm_arm_resume_guest(struct kvm *kvm)
 
 	kvm_for_each_vcpu(i, vcpu, kvm) {
 		vcpu->arch.pause = false;
-		rcuwait_wake_up(kvm_arch_vcpu_get_wait(vcpu));
+		__kvm_vcpu_wake_up(vcpu);
 	}
 }
 

arch/x86/kvm/lapic.c

@@ -1931,7 +1931,7 @@ void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu)
 	/* If the preempt notifier has already run, it also called apic_timer_expired */
 	if (!apic->lapic_timer.hv_timer_in_use)
 		goto out;
-	WARN_ON(rcuwait_active(&vcpu->wait));
+	WARN_ON(kvm_vcpu_is_blocking(vcpu));
 	apic_timer_expired(apic, false);
 	cancel_hv_timer(apic);
 

include/linux/kvm_host.h

@@ -1286,6 +1286,20 @@ static inline struct rcuwait *kvm_arch_vcpu_get_wait(struct kvm_vcpu *vcpu)
 #endif
 }
 
+/*
+ * Wake a vCPU if necessary, but don't do any stats/metadata updates.  Returns
+ * true if the vCPU was blocking and was awakened, false otherwise.
+ */
+static inline bool __kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
+{
+	return !!rcuwait_wake_up(kvm_arch_vcpu_get_wait(vcpu));
+}
+
+static inline bool kvm_vcpu_is_blocking(struct kvm_vcpu *vcpu)
+{
+	return rcuwait_active(kvm_arch_vcpu_get_wait(vcpu));
+}
+
 #ifdef __KVM_HAVE_ARCH_INTC_INITIALIZED
 /*
  * returns true if the virtual interrupt controller is initialized and

virt/kvm/async_pf.c

@@ -85,7 +85,7 @@ static void async_pf_execute(struct work_struct *work)
 
 	trace_kvm_async_pf_completed(addr, cr2_or_gpa);
 
-	rcuwait_wake_up(kvm_arch_vcpu_get_wait(vcpu));
+	__kvm_vcpu_wake_up(vcpu);
 
 	mmput(mm);
 	kvm_put_kvm(vcpu->kvm);

virt/kvm/kvm_main.c

@@ -3403,10 +3403,7 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_halt);
 
 bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
 {
-	struct rcuwait *waitp;
-
-	waitp = kvm_arch_vcpu_get_wait(vcpu);
-	if (rcuwait_wake_up(waitp)) {
+	if (__kvm_vcpu_wake_up(vcpu)) {
 		WRITE_ONCE(vcpu->ready, true);
 		++vcpu->stat.generic.halt_wakeup;
 		return true;
@@ -3574,8 +3571,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
 				continue;
 			if (vcpu == me)
 				continue;
-			if (rcuwait_active(kvm_arch_vcpu_get_wait(vcpu)) &&
-			    !vcpu_dy_runnable(vcpu))
+			if (kvm_vcpu_is_blocking(vcpu) && !vcpu_dy_runnable(vcpu))
 				continue;
 			if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode &&
 			    !kvm_arch_dy_has_pending_interrupt(vcpu) &&