Re: [PATCH v3 11/11] KVM: MMU: apply page track notifier

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On 02/19/2016 07:56 PM, Paolo Bonzini wrote:


On 14/02/2016 12:31, Xiao Guangrong wrote:
Register the notifier to receive write track event so that we can update
our shadow page table

It makes kvm_mmu_pte_write() be the callback of the notifier, no function
is changed

Signed-off-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
---
  arch/x86/include/asm/kvm_host.h |  5 +++--
  arch/x86/kvm/mmu.c              | 19 +++++++++++++++++--
  arch/x86/kvm/x86.c              |  4 ++--
  3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 254d103..5246f07 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -696,6 +696,7 @@ struct kvm_arch {
  	 */
  	struct list_head active_mmu_pages;
  	struct list_head zapped_obsolete_pages;
+	struct kvm_page_track_notifier_node mmu_sp_tracker;
  	struct kvm_page_track_notifier_head track_notifier_head;

  	struct list_head assigned_dev_head;
@@ -994,6 +995,8 @@ void kvm_mmu_module_exit(void);
  void kvm_mmu_destroy(struct kvm_vcpu *vcpu);
  int kvm_mmu_create(struct kvm_vcpu *vcpu);
  void kvm_mmu_setup(struct kvm_vcpu *vcpu);
+void kvm_mmu_init_vm(struct kvm *kvm);
+void kvm_mmu_uninit_vm(struct kvm *kvm);
  void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,
  		u64 dirty_mask, u64 nx_mask, u64 x_mask);

@@ -1133,8 +1136,6 @@ void kvm_pic_clear_all(struct kvm_pic *pic, int irq_source_id);

  void kvm_inject_nmi(struct kvm_vcpu *vcpu);

-void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
-		       const u8 *new, int bytes);
  int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn);
  int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva);
  void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f924e6c..57cf30b 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -4316,8 +4316,8 @@ static u64 *get_written_sptes(struct kvm_mmu_page *sp, gpa_t gpa, int *nspte)
  	return spte;
  }

-void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
-		       const u8 *new, int bytes)
+static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
+			      const u8 *new, int bytes)
  {
  	gfn_t gfn = gpa >> PAGE_SHIFT;
  	struct kvm_mmu_page *sp;
@@ -4531,6 +4531,21 @@ void kvm_mmu_setup(struct kvm_vcpu *vcpu)
  	init_kvm_mmu(vcpu);
  }

+void kvm_mmu_init_vm(struct kvm *kvm)
+{
+	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
+
+	node->track_write = kvm_mmu_pte_write;
+	kvm_page_track_register_notifier(kvm, node);
+}
+
+void kvm_mmu_uninit_vm(struct kvm *kvm)
+{
+	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
+
+	kvm_page_track_unregister_notifier(kvm, node);
+}
+
  /* The return value indicates if tlb flush on all vcpus is needed. */
  typedef bool (*slot_level_handler) (struct kvm *kvm, struct kvm_rmap_head *rmap_head);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 98019b6..319d572 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4369,7 +4369,6 @@ int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
  	ret = kvm_vcpu_write_guest(vcpu, gpa, val, bytes);
  	if (ret < 0)
  		return 0;
-	kvm_mmu_pte_write(vcpu, gpa, val, bytes);
  	kvm_page_track_write(vcpu, gpa, val, bytes);
  	return 1;
  }
@@ -4628,7 +4627,6 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
  		return X86EMUL_CMPXCHG_FAILED;

  	kvm_vcpu_mark_page_dirty(vcpu, gpa >> PAGE_SHIFT);
-	kvm_mmu_pte_write(vcpu, gpa, new, bytes);
  	kvm_page_track_write(vcpu, gpa, new, bytes);

  	return X86EMUL_CONTINUE;
@@ -7751,6 +7749,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
  	INIT_DELAYED_WORK(&kvm->arch.kvmclock_sync_work, kvmclock_sync_fn);

  	kvm_page_track_init(kvm);
+	kvm_mmu_init_vm(kvm);

  	return 0;
  }
@@ -7878,6 +7877,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
  	kfree(kvm->arch.vioapic);
  	kvm_free_vcpus(kvm);
  	kfree(rcu_dereference_check(kvm->arch.apic_map, 1));
+	kvm_mmu_uninit_vm(kvm);

This function is not necessary, since the VM is disappearing anyway and
the page tracker is not going to be called.

I think it is still necessary, as we are using srcu to protect the notifier, so
we should wait all the callers of notifier callbacks gone, i.e, synchronize_srcu()
is needed anyway.

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