Re: [PATCH 07/11] KVM: page track: add notifier support

[Jike Song]

On 12/01/2015 02:26 AM, Xiao Guangrong wrote:

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 
---
  arch/x86/include/asm/kvm_host.h   |  1 +
  arch/x86/include/asm/kvm_page_track.h | 39 
  arch/x86/kvm/page_track.c | 67 +++
  arch/x86/kvm/x86.c|  4 +++
  4 files changed, 111 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index afff1f1..0f7b940 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -658,6 +658,7 @@ 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 f223201..6744234 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);


Sir, is it possible to make this non-void? as you described below, the
callback may find this gpa isn't the page being tracked, so it probably
want to return something to indicate: not my business, continue :)


+};
+
+void kvm_page_track_init(struct kvm *kvm);
+
  int kvm_page_track_create_memslot(struct kvm_memory_slot *slot,
  unsigned long npages);
  void kvm_page_track_free_memslot(struct kvm_memory_slot *free,
@@ -17,4 +47,13 @@ void kvm_page_track_remove_page(struct kvm *kvm, gfn_t gfn,
enum kvm_page_track_mode mode);
  bool kvm_page_track_check_mode(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
diff --git a/arch/x86/kvm/page_track.c b/arch/x86/kvm/page_track.c
index dc2da12..84420df 100644
--- a/arch/x86/kvm/page_track.c
+++ b/arch/x86/kvm/page_track.c
@@ -165,3 +165,70 @@ bool kvm_page_track_check_mode(struct kvm_vcpu *vcpu, 
gfn_t gfn,

return !!ACCESS_ONCE(slot->arch.gfn_track[mode][index]);
  }
+
+void kvm_page_track_init(struct kvm *kvm)
+{
+   struct kvm_page_track_notifier_head *head;
+
+   head = >arch.track_notifier_head;
+   init_srcu_struct(>track_srcu);
+   INIT_HLIST_HEAD(>track_notifier_list);
+}
+
+/*
+ * register the notifier so that event interception for the tracked guest
+ * pages can be received.
+ */
+void
+kvm_page_track_register_notifier(struct kvm *kvm,
+struct kvm_page_track_notifier_node *n)
+{
+   struct kvm_page_track_notifier_head *head;
+
+   head = >arch.track_notifier_head;
+
+   spin_lock(>mmu_lock);
+   hlist_add_head_rcu(>node, >track_notifier_list);
+   spin_unlock(>mmu_lock);
+}
+
+/*
+ * stop receiving the event interception. It is the opposed operation of
+ * kvm_page_track_register_notifier().
+ */
+void
+kvm_page_track_unregister_notifier(struct kvm *kvm,
+  struct kvm_page_track_notifier_node *n)
+{
+   struct kvm_page_track_notifier_head *head;
+
+   

Re: [PATCH 07/11] KVM: page track: add notifier support

[Xiao Guangrong]

On 12/16/2015 01:53 PM, Jike Song wrote:

On 12/01/2015 02:26 AM, Xiao Guangrong wrote:

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 
---
  arch/x86/include/asm/kvm_host.h   |  1 +
  arch/x86/include/asm/kvm_page_track.h | 39 
  arch/x86/kvm/page_track.c | 67 +++
  arch/x86/kvm/x86.c|  4 +++
  4 files changed, 111 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index afff1f1..0f7b940 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -658,6 +658,7 @@ 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 f223201..6744234 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);


Sir, is it possible to make this non-void? as you described below, the
callback may find this gpa isn't the page being tracked, so it probably
want to return something to indicate: not my business, continue :)


Currently the return value is useless and it is not ABI so we can extend
it if it is needed in the future.

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[PATCH 07/11] KVM: page track: add notifier support

[Xiao Guangrong]

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 
---
 arch/x86/include/asm/kvm_host.h   |  1 +
 arch/x86/include/asm/kvm_page_track.h | 39 
 arch/x86/kvm/page_track.c | 67 +++
 arch/x86/kvm/x86.c|  4 +++
 4 files changed, 111 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index afff1f1..0f7b940 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -658,6 +658,7 @@ 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 f223201..6744234 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);
+
 int kvm_page_track_create_memslot(struct kvm_memory_slot *slot,
  unsigned long npages);
 void kvm_page_track_free_memslot(struct kvm_memory_slot *free,
@@ -17,4 +47,13 @@ void kvm_page_track_remove_page(struct kvm *kvm, gfn_t gfn,
enum kvm_page_track_mode mode);
 bool kvm_page_track_check_mode(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
diff --git a/arch/x86/kvm/page_track.c b/arch/x86/kvm/page_track.c
index dc2da12..84420df 100644
--- a/arch/x86/kvm/page_track.c
+++ b/arch/x86/kvm/page_track.c
@@ -165,3 +165,70 @@ bool kvm_page_track_check_mode(struct kvm_vcpu *vcpu, 
gfn_t gfn,
 
return !!ACCESS_ONCE(slot->arch.gfn_track[mode][index]);
 }
+
+void kvm_page_track_init(struct kvm *kvm)
+{
+   struct kvm_page_track_notifier_head *head;
+
+   head = >arch.track_notifier_head;
+   init_srcu_struct(>track_srcu);
+   INIT_HLIST_HEAD(>track_notifier_list);
+}
+
+/*
+ * register the notifier so that event interception for the tracked guest
+ * pages can be received.
+ */
+void
+kvm_page_track_register_notifier(struct kvm *kvm,
+struct kvm_page_track_notifier_node *n)
+{
+   struct kvm_page_track_notifier_head *head;
+
+   head = >arch.track_notifier_head;
+
+   spin_lock(>mmu_lock);
+   hlist_add_head_rcu(>node, >track_notifier_list);
+   spin_unlock(>mmu_lock);
+}
+
+/*
+ * stop receiving the event interception. It is the opposed operation of
+ * kvm_page_track_register_notifier().
+ */
+void
+kvm_page_track_unregister_notifier(struct kvm *kvm,
+  struct kvm_page_track_notifier_node *n)
+{
+   struct kvm_page_track_notifier_head *head;
+
+   head = >arch.track_notifier_head;
+
+   spin_lock(>mmu_lock);
+   hlist_del_rcu(>node);
+   spin_unlock(>mmu_lock);
+   synchronize_srcu(>track_srcu);
+}
+
+/*
+ * Notify the node that write access is intercepted and write emulation is
+ * finished at