On Mon, Oct 10, 2016 at 07:06:27PM +0200, Paolo Bonzini wrote:
>
>
> On 09/10/2016 10:31, Neo Jia wrote:
> > 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?
>
> Hi Neo,
>
> AFAIK this is needed because KVMGT doesn't paravirtualize the PPGTT,
> while nVidia does.
> "From Xiaoguang:
> This is related to KVMGT device model.
> For KVMGT some ram will be allocated and used as ppgtt page table and
> the page table is write protected.
> We use page track to implement write protect. But get problem while
> memslot is moved or removed.
> We must clear the write protect for the pages in the memslot or there
> will be errors while ppgtt do cleanup.
> So KVMGT must register the track_flush_slot to get notified while
> memslot is moved or removed."
(merging thread)
Hi Paolo and Xiaoguang,
I am just wondering how device driver can register a notifier so he can be
notified for write-protected pages when writes are happening.
Thanks,
Neo
>
> Paolo
>
> > Thanks,
> > Neo
> >
> >>
> >> Reviewed-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxx>
> >> Signed-off-by: Chen Xiaoguang <xiaoguang.chen@xxxxxxxxx>
> >> ---
> >> 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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