Re: [PATCH 1/2] KVM: page track: add a new notifier type: track_flush_slot

[Neo Jia <cjia@nvidia.com>]

On Sun, Oct 09, 2016 at 03:41:43PM +0800, Xiaoguang Chen wrote:
> When a memory slot is being moved or removed users of page track
> can be notified. So users can drop write-protection for the pages
> in that memory slot.
> 
> This notifier type is needed by KVMGT to sync up its shadow page
> table when memory slot is being moved or removed.

Hi Xiaoguang,

How is this supposed to be used by the kvmgt?

Thanks,
Neo

> 
> Reviewed-by: Xiao Guangrong <guangrong.xiao@intel.com>
> Signed-off-by: Chen Xiaoguang <xiaoguang.chen@intel.com>
> ---
>  arch/x86/include/asm/kvm_page_track.h |  9 +++++++++
>  arch/x86/kvm/page_track.c             | 25 +++++++++++++++++++++++++
>  arch/x86/kvm/x86.c                    |  2 +-
>  3 files changed, 35 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h
> index c2b8d24..5f66597 100644
> --- a/arch/x86/include/asm/kvm_page_track.h
> +++ b/arch/x86/include/asm/kvm_page_track.h
> @@ -32,6 +32,14 @@ struct kvm_page_track_notifier_node {
>  	 */
>  	void (*track_write)(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
>  			    int bytes);
> +	/*
> +	 * It is called when memory slot is being moved or removed
> +	 * users can drop write-protection for the pages in that memory slot
> +	 *
> +	 * @kvm: the kvm where memory slot being moved or removed
> +	 * @slot: the memory slot being moved or removed
> +	 */
> +	void (*track_flush_slot)(struct kvm *kvm, struct kvm_memory_slot *slot);
>  };
>  
>  void kvm_page_track_init(struct kvm *kvm);
> @@ -58,4 +66,5 @@ 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);
> +void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot);
>  #endif
> diff --git a/arch/x86/kvm/page_track.c b/arch/x86/kvm/page_track.c
> index b431539..e79bb25 100644
> --- a/arch/x86/kvm/page_track.c
> +++ b/arch/x86/kvm/page_track.c
> @@ -225,3 +225,28 @@ void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
>  			n->track_write(vcpu, gpa, new, bytes);
>  	srcu_read_unlock(&head->track_srcu, idx);
>  }
> +
> +/*
> + * Notify the node that memory slot is being removed or moved so that it can
> + * drop write-protection for the pages in the memory slot.
> + *
> + * The node should figure out it has any write-protected pages in this slot
> + * by itself.
> + */
> +void kvm_page_track_flush_slot(struct kvm *kvm, struct kvm_memory_slot *slot)
> +{
> +	struct kvm_page_track_notifier_head *head;
> +	struct kvm_page_track_notifier_node *n;
> +	int idx;
> +
> +	head = &kvm->arch.track_notifier_head;
> +
> +	if (hlist_empty(&head->track_notifier_list))
> +		return;
> +
> +	idx = srcu_read_lock(&head->track_srcu);
> +	hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
> +		if (n->track_flush_slot)
> +			n->track_flush_slot(kvm, slot);
> +	srcu_read_unlock(&head->track_srcu, idx);
> +}
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 87f5dbb..f8ae90c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8278,7 +8278,7 @@ void kvm_arch_flush_shadow_all(struct kvm *kvm)
>  void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
>  				   struct kvm_memory_slot *slot)
>  {
> -	kvm_mmu_invalidate_zap_all_pages(kvm);
> +	kvm_page_track_flush_slot(kvm, slot);
>  }
>  
>  static inline bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
> -- 
> 1.9.1
> 
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