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

[Paolo Bonzini]

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.

Paolo