KVM: handle more completed apfs if possible

If it's no need to inject async #PF to PV guest we can handle
more completed apfs at one time, so we can retry guest #PF
as early as possible
Signed-off-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Acked-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

virt/kvm/async_pf.c

@@ -124,12 +124,11 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 {
 	struct kvm_async_pf *work;
 
-	if (list_empty_careful(&vcpu->async_pf.done) ||
-	    !kvm_arch_can_inject_async_page_present(vcpu))
-		return;
-
+	while (!list_empty_careful(&vcpu->async_pf.done) &&
+	      kvm_arch_can_inject_async_page_present(vcpu)) {
 		spin_lock(&vcpu->async_pf.lock);
-	work = list_first_entry(&vcpu->async_pf.done, typeof(*work), link);
+		work = list_first_entry(&vcpu->async_pf.done, typeof(*work),
+					      link);
 		list_del(&work->link);
 		spin_unlock(&vcpu->async_pf.lock);
 
@@ -142,6 +141,7 @@ void kvm_check_async_pf_completion(struct kvm_vcpu *vcpu)
 		if (work->page)
 			put_page(work->page);
 		kmem_cache_free(async_pf_cache, work);
+	}
 }
 
 int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, gfn_t gfn,