Re: [PATCH 05/11] KVM: page track: introduce kvm_page_track_{add,remove}_page

[Kai Huang]

On 12/15/2015 03:15 PM, Kai Huang wrote:
> 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@xxxxxxxxxxxxxxx>
> > ---
> >   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?
Forget this reply. Looks my thunderbird has something wrong and couldn't 
show your whole patch series, and I missed patch 1~3. Now I see them. Sorry.

Thanks,
-Kai
> 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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