KVM: page track: add notifier support

Notifier list is introduced so that any node wants to receive the track
event can register to the list

Two APIs are introduced here:
- kvm_page_track_register_notifier(): register the notifier to receive
  track event

- kvm_page_track_unregister_notifier(): stop receiving track event by
  unregister the notifier

The callback, node->track_write() is called when a write access on the
write tracked page happens

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 40 insertions, 0 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e2fc5c0ec86a..eb68e6aca0cf 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -704,6 +704,7 @@ struct kvm_arch {
 	 */
 	struct list_head active_mmu_pages;
 	struct list_head zapped_obsolete_pages;
+	struct kvm_page_track_notifier_head track_notifier_head;
 
 	struct list_head assigned_dev_head;
 	struct iommu_domain *iommu_domain;
diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h
index 5f16e2864e73..c2b8d24a235c 100644
--- a/arch/x86/include/asm/kvm_page_track.h
+++ b/arch/x86/include/asm/kvm_page_track.h
@@ -6,6 +6,36 @@ enum kvm_page_track_mode {
 	KVM_PAGE_TRACK_MAX,
 };
 
+/*
+ * The notifier represented by @kvm_page_track_notifier_node is linked into
+ * the head which will be notified when guest is triggering the track event.
+ *
+ * Write access on the head is protected by kvm->mmu_lock, read access
+ * is protected by track_srcu.
+ */
+struct kvm_page_track_notifier_head {
+	struct srcu_struct track_srcu;
+	struct hlist_head track_notifier_list;
+};
+
+struct kvm_page_track_notifier_node {
+	struct hlist_node node;
+
+	/*
+	 * It is called when guest is writing the write-tracked page
+	 * and write emulation is finished at that time.
+	 *
+	 * @vcpu: the vcpu where the write access happened.
+	 * @gpa: the physical address written by guest.
+	 * @new: the data was written to the address.
+	 * @bytes: the written length.
+	 */
+	void (*track_write)(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
+			    int bytes);
+};
+
+void kvm_page_track_init(struct kvm *kvm);
+
 void kvm_page_track_free_memslot(struct kvm_memory_slot *free,
 				 struct kvm_memory_slot *dont);
 int kvm_page_track_create_memslot(struct kvm_memory_slot *slot,
@@ -19,4 +49,13 @@ void kvm_slot_page_track_remove_page(struct kvm *kvm,
 				     enum kvm_page_track_mode mode);
 bool kvm_page_track_is_active(struct kvm_vcpu *vcpu, gfn_t gfn,
 			      enum kvm_page_track_mode mode);
+
+void
+kvm_page_track_register_notifier(struct kvm *kvm,
+				 struct kvm_page_track_notifier_node *n);
+void
+kvm_page_track_unregister_notifier(struct kvm *kvm,
+				   struct kvm_page_track_notifier_node *n);
+void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
+			  int bytes);
 #endif