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 <guangrong.xiao@xxxxxxxxxxxxxxx>
> ---
>   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 = &kvm->arch.track_notifier_head;
> +	init_srcu_struct(&head->track_srcu);
> +	INIT_HLIST_HEAD(&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 = &kvm->arch.track_notifier_head;
> +
> +	spin_lock(&kvm->mmu_lock);
> +	hlist_add_head_rcu(&n->node, &head->track_notifier_list);
> +	spin_unlock(&kvm->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 = &kvm->arch.track_notifier_head;
> +
> +	spin_lock(&kvm->mmu_lock);
> +	hlist_del_rcu(&n->node);
> +	spin_unlock(&kvm->mmu_lock);
> +	synchronize_srcu(&head->track_srcu);
> +}
> +
> +/*
> + * Notify the node that write access is intercepted and write emulation is
> + * finished at this time.
> + *
> + * The node should figure out if the written page is the one that node is
> + * interested in by itself.
> + */
> +void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
> +			  int bytes)
> +{
> +	struct kvm_page_track_notifier_head *head;
> +	struct kvm_page_track_notifier_node *n;
> +	int idx;
> +
> +	head = &vcpu->kvm->arch.track_notifier_head;
> +
> +	idx = srcu_read_lock(&head->track_srcu);
> +	hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
> +		if (n->track_write)
> +			n->track_write(vcpu, gpa, new, bytes);
> +	srcu_read_unlock(&head->track_srcu, idx);
> +}
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index ad4888a..64dbc69 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4328,6 +4328,7 @@ int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
>   	if (ret < 0)
>   		return 0;
>   	kvm_mmu_pte_write(vcpu, gpa, val, bytes);
> +	kvm_page_track_write(vcpu, gpa, val, bytes);
>   	return 1;
>   }
>
> @@ -4586,6 +4587,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
>
>   	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;
>
> @@ -7691,6 +7693,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>   	INIT_DELAYED_WORK(&kvm->arch.kvmclock_update_work, kvmclock_update_fn);
>   	INIT_DELAYED_WORK(&kvm->arch.kvmclock_sync_work, kvmclock_sync_fn);
>
> +	kvm_page_track_init(kvm);
> +
>   	return 0;
>   }
--
Thanks,
Jike
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