[PATCH v2 02/17] KVM: async_pf: Add helper function to check completion queue

[Gavin Shan]

This adds inline function kvm_check_async_pf_completion_queue()
and stub on !CONFIG_KVM_ASYNC_PF so that the source code won't
have to care about CONFIG_KVM_ASYNC_PF. The kernel option is
used for once in kvm_main.c and it can be removed then. Besides,
the checks on the completion queue are all replaced by the newly
introduced helper as list_empty() and list_empty_careful() are
interchangeable.

The stub kvm_check_async_pf_completion() on !CONFIG_KVM_ASYNC_PF
is also introduced. It will be used by subsequent patch.

Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
---
 arch/x86/kvm/x86.c       |  2 +-
 include/linux/kvm_host.h | 12 ++++++++++++
 virt/kvm/async_pf.c      | 12 ++++++------
 virt/kvm/kvm_main.c      |  4 +---
 4 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 76bce832cade..f3c9fe5c424e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10794,7 +10794,7 @@ static inline bool kvm_guest_apic_has_interrupt(struct kvm_vcpu *vcpu)
 
 static inline bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
 {
-	if (!list_empty_careful(&vcpu->async_pf.done))
+	if (kvm_check_async_pf_completion_queue(vcpu))
 		return true;
 
 	if (kvm_apic_has_events(vcpu))
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b6697ee1182e..041d93f8f4b0 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -316,11 +316,23 @@ struct kvm_async_pf {
 	bool				notpresent_injected;
 };
 
+static inline bool kvm_check_async_pf_completion_queue(struct kvm_vcpu *vcpu)
+{
+	return !list_empty_careful(&vcpu->async_pf.done);
+}
+
 void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu);
 void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu);
 bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 			unsigned long hva, struct kvm_arch_async_pf *arch);
 int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu);
+#else
+static inline bool kvm_check_async_pf_completion_queue(struct kvm_vcpu *vcpu)
+{
+	return false;
+}
+
+static inline void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu) { }
 #endif
 
 
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index dd777688d14a..2cf864aafd0e 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -70,7 +70,7 @@ static void async_pf_execute(struct work_struct *work)
 		kvm_arch_async_page_present(vcpu, apf);
 
 	spin_lock(&vcpu->async_pf.lock);
-	first = list_empty(&vcpu->async_pf.done);
+	first = !kvm_check_async_pf_completion_queue(vcpu);
 	list_add_tail(&apf->link, &vcpu->async_pf.done);
 	apf->vcpu = NULL;
 	spin_unlock(&vcpu->async_pf.lock);
@@ -122,7 +122,7 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu)
 		spin_lock(&vcpu->async_pf.lock);
 	}
 
-	while (!list_empty(&vcpu->async_pf.done)) {
+	while (kvm_check_async_pf_completion_queue(vcpu)) {
 		struct kvm_async_pf *work =
 			list_first_entry(&vcpu->async_pf.done,
 					 typeof(*work), link);
@@ -138,8 +138,8 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 {
 	struct kvm_async_pf *work;
 
-	while (!list_empty_careful(&vcpu->async_pf.done) &&
-	      kvm_arch_can_dequeue_async_page_present(vcpu)) {
+	while (kvm_check_async_pf_completion_queue(vcpu) &&
+	       kvm_arch_can_dequeue_async_page_present(vcpu)) {
 		spin_lock(&vcpu->async_pf.lock);
 		work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
 					      link);
@@ -205,7 +205,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
 	struct kvm_async_pf *work;
 	bool first;
 
-	if (!list_empty_careful(&vcpu->async_pf.done))
+	if (kvm_check_async_pf_completion_queue(vcpu))
 		return 0;
 
 	work = kmem_cache_zalloc(async_pf_cache, GFP_ATOMIC);
@@ -216,7 +216,7 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
 	INIT_LIST_HEAD(&work->queue); /* for list_del to work */
 
 	spin_lock(&vcpu->async_pf.lock);
-	first = list_empty(&vcpu->async_pf.done);
+	first = !kvm_check_async_pf_completion_queue(vcpu);
 	list_add_tail(&work->link, &vcpu->async_pf.done);
 	spin_unlock(&vcpu->async_pf.lock);
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 8367d88ce39b..632b80b6e485 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2961,10 +2961,8 @@ static bool vcpu_dy_runnable(struct kvm_vcpu *vcpu)
 	if (kvm_arch_dy_runnable(vcpu))
 		return true;
 
-#ifdef CONFIG_KVM_ASYNC_PF
-	if (!list_empty_careful(&vcpu->async_pf.done))
+	if (kvm_check_async_pf_completion_queue(vcpu))
 		return true;
-#endif
 
 	return false;
 }
-- 
2.23.0