Subject: Re: [PATCH 05/11] KVM: page track: introduce
 kvm_page_track_{add,remove}_page
To: Xiao Guangrong <guangrong.xiao@linux.intel.com>, pbonzini@redhat.com
References: <1448907973-36066-1-git-send-email-guangrong.xiao@linux.intel.com>
 <1448907973-36066-6-git-send-email-guangrong.xiao@linux.intel.com>
Cc: gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
From: Kai Huang <kai.huang@linux.intel.com>
Message-ID: <566FBDF6.9010009@linux.intel.com>
Date: Tue, 15 Dec 2015 15:15:02 +0800
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On 12/01/2015 02:26 AM, Xiao Guangrong wrote:
> These two functions are the user APIs:
> - kvm_page_track_add_page(): add the page to the tracking pool after
>    that later specified access on that page will be tracked
>
> - kvm_page_track_remove_page(): remove the page from the tracking pool,
>    the specified access on the page is not tracked after the last user is
>    gone
>
> Both of these are called under the protection of kvm->srcu or
> kvm->slots_lock
>
> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
> ---
>   arch/x86/include/asm/kvm_page_track.h |  5 ++
>   arch/x86/kvm/page_track.c             | 95 +++++++++++++++++++++++++++++++++++
>   2 files changed, 100 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h
> index 347d5c9..9cc17c6 100644
> --- a/arch/x86/include/asm/kvm_page_track.h
> +++ b/arch/x86/include/asm/kvm_page_track.h
> @@ -10,4 +10,9 @@ 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,
>   				 struct kvm_memory_slot *dont);
> +
> +void kvm_page_track_add_page(struct kvm *kvm, gfn_t gfn,
> +			     enum kvm_page_track_mode mode);
> +void kvm_page_track_remove_page(struct kvm *kvm, gfn_t gfn,
> +				enum kvm_page_track_mode mode);
>   #endif
> diff --git a/arch/x86/kvm/page_track.c b/arch/x86/kvm/page_track.c
> index 0338d36..ad510db 100644
> --- a/arch/x86/kvm/page_track.c
> +++ b/arch/x86/kvm/page_track.c
> @@ -56,3 +56,98 @@ void kvm_page_track_free_memslot(struct kvm_memory_slot *free,
>   	if (!dont || free->arch.gfn_track != dont->arch.gfn_track)
>   		page_track_slot_free(free);
>   }
> +
> +static bool check_mode(enum kvm_page_track_mode mode)
> +{
> +	if (mode < 0 || mode >= KVM_PAGE_TRACK_MAX)
> +		return false;
> +
> +	return true;
> +}
> +
> +static void update_gfn_track(struct kvm_memory_slot *slot, gfn_t gfn,
> +			     enum kvm_page_track_mode mode, int count)
> +{
> +	int index, val;
> +
> +	index = gfn_to_index(gfn, slot->base_gfn, PT_PAGE_TABLE_LEVEL);
> +
> +	slot->arch.gfn_track[mode][index] += count;
> +	val = slot->arch.gfn_track[mode][index];
> +	WARN_ON(val < 0);
> +}
> +
> +/*
> + * add guest page to the tracking pool so that corresponding access on that
> + * page will be intercepted.
> + *
> + * It should be called under the protection of kvm->srcu or kvm->slots_lock
> + *
> + * @kvm: the guest instance we are interested in.
> + * @gfn: the guest page.
> + * @mode: tracking mode, currently only write track is supported.
> + */
> +void kvm_page_track_add_page(struct kvm *kvm, gfn_t gfn,
> +			     enum kvm_page_track_mode mode)
> +{
> +	struct kvm_memslots *slots;
> +	struct kvm_memory_slot *slot;
> +	int i;
> +
> +	WARN_ON(!check_mode(mode));
> +
> +	for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
> +		slots = __kvm_memslots(kvm, i);
> +		slot = __gfn_to_memslot(slots, gfn);
> +
> +		spin_lock(&kvm->mmu_lock);
> +		update_gfn_track(slot, gfn, mode, 1);
> +
> +		/*
> +		 * new track stops large page mapping for the
> +		 * tracked page.
> +		 */
> +		kvm_mmu_gfn_disallow_lpage(slot, gfn);
Where is  kvm_mmu_gfn_disallow_lpage? Neither did I see it in your patch 
nor in my own latest KVM repo without your patch :)

> +
> +		if (mode == KVM_PAGE_TRACK_WRITE)
> +			if (kvm_mmu_slot_gfn_write_protect(kvm, slot, gfn))
> +				kvm_flush_remote_tlbs(kvm);
Neither can I find kvm_mmu_slot_gfn_write_protect. Did I miss something?

Thanks,
-Kai
> +		spin_unlock(&kvm->mmu_lock);
> +	}
> +}
> +
> +/*
> + * remove the guest page from the tracking pool which stops the interception
> + * of corresponding access on that page. It is the opposed operation of
> + * kvm_page_track_add_page().
> + *
> + * It should be called under the protection of kvm->srcu or kvm->slots_lock
> + *
> + * @kvm: the guest instance we are interested in.
> + * @gfn: the guest page.
> + * @mode: tracking mode, currently only write track is supported.
> + */
> +void kvm_page_track_remove_page(struct kvm *kvm, gfn_t gfn,
> +				enum kvm_page_track_mode mode)
> +{
> +	struct kvm_memslots *slots;
> +	struct kvm_memory_slot *slot;
> +	int i;
> +
> +	WARN_ON(!check_mode(mode));
> +
> +	for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
> +		slots = __kvm_memslots(kvm, i);
> +		slot = __gfn_to_memslot(slots, gfn);
> +
> +		spin_lock(&kvm->mmu_lock);
> +		update_gfn_track(slot, gfn, mode, -1);
> +
> +		/*
> +		 * allow large page mapping for the tracked page
> +		 * after the tracker is gone.
> +		 */
> +		kvm_mmu_gfn_allow_lpage(slot, gfn);
> +		spin_unlock(&kvm->mmu_lock);
> +	}
> +}

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