Re: [PATCH v3 11/11] KVM: MMU: apply page track notifier

[Xiao Guangrong]

On 02/19/2016 07:56 PM, Paolo Bonzini wrote:
> On 14/02/2016 12:31, Xiao Guangrong wrote:
> > Register the notifier to receive write track event so that we can update
> > our shadow page table
> >
> > It makes kvm_mmu_pte_write() be the callback of the notifier, no function
> > is changed
> >
> > Signed-off-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
> > ---
> >   arch/x86/include/asm/kvm_host.h |  5 +++--
> >   arch/x86/kvm/mmu.c              | 19 +++++++++++++++++--
> >   arch/x86/kvm/x86.c              |  4 ++--
> >   3 files changed, 22 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 254d103..5246f07 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -696,6 +696,7 @@ struct kvm_arch {
> >   	 */
> >   	struct list_head active_mmu_pages;
> >   	struct list_head zapped_obsolete_pages;
> > +	struct kvm_page_track_notifier_node mmu_sp_tracker;
> >   	struct kvm_page_track_notifier_head track_notifier_head;
> >
> >   	struct list_head assigned_dev_head;
> > @@ -994,6 +995,8 @@ void kvm_mmu_module_exit(void);
> >   void kvm_mmu_destroy(struct kvm_vcpu *vcpu);
> >   int kvm_mmu_create(struct kvm_vcpu *vcpu);
> >   void kvm_mmu_setup(struct kvm_vcpu *vcpu);
> > +void kvm_mmu_init_vm(struct kvm *kvm);
> > +void kvm_mmu_uninit_vm(struct kvm *kvm);
> >   void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,
> >   		u64 dirty_mask, u64 nx_mask, u64 x_mask);
> >
> > @@ -1133,8 +1136,6 @@ void kvm_pic_clear_all(struct kvm_pic *pic, int irq_source_id);
> >
> >   void kvm_inject_nmi(struct kvm_vcpu *vcpu);
> >
> > -void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
> > -		       const u8 *new, int bytes);
> >   int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn);
> >   int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva);
> >   void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
> > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > index f924e6c..57cf30b 100644
> > --- a/arch/x86/kvm/mmu.c
> > +++ b/arch/x86/kvm/mmu.c
> > @@ -4316,8 +4316,8 @@ static u64 *get_written_sptes(struct kvm_mmu_page *sp, gpa_t gpa, int *nspte)
> >   	return spte;
> >   }
> >
> > -void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
> > -		       const u8 *new, int bytes)
> > +static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
> > +			      const u8 *new, int bytes)
> >   {
> >   	gfn_t gfn = gpa >> PAGE_SHIFT;
> >   	struct kvm_mmu_page *sp;
> > @@ -4531,6 +4531,21 @@ void kvm_mmu_setup(struct kvm_vcpu *vcpu)
> >   	init_kvm_mmu(vcpu);
> >   }
> >
> > +void kvm_mmu_init_vm(struct kvm *kvm)
> > +{
> > +	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
> > +
> > +	node->track_write = kvm_mmu_pte_write;
> > +	kvm_page_track_register_notifier(kvm, node);
> > +}
> > +
> > +void kvm_mmu_uninit_vm(struct kvm *kvm)
> > +{
> > +	struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
> > +
> > +	kvm_page_track_unregister_notifier(kvm, node);
> > +}
> > +
> >   /* The return value indicates if tlb flush on all vcpus is needed. */
> >   typedef bool (*slot_level_handler) (struct kvm *kvm, struct kvm_rmap_head *rmap_head);
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 98019b6..319d572 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -4369,7 +4369,6 @@ int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
> >   	ret = kvm_vcpu_write_guest(vcpu, gpa, val, bytes);
> >   	if (ret < 0)
> >   		return 0;
> > -	kvm_mmu_pte_write(vcpu, gpa, val, bytes);
> >   	kvm_page_track_write(vcpu, gpa, val, bytes);
> >   	return 1;
> >   }
> > @@ -4628,7 +4627,6 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
> >   		return X86EMUL_CMPXCHG_FAILED;
> >
> >   	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;
> > @@ -7751,6 +7749,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> >   	INIT_DELAYED_WORK(&kvm->arch.kvmclock_sync_work, kvmclock_sync_fn);
> >
> >   	kvm_page_track_init(kvm);
> > +	kvm_mmu_init_vm(kvm);
> >
> >   	return 0;
> >   }
> > @@ -7878,6 +7877,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
> >   	kfree(kvm->arch.vioapic);
> >   	kvm_free_vcpus(kvm);
> >   	kfree(rcu_dereference_check(kvm->arch.apic_map, 1));
> > +	kvm_mmu_uninit_vm(kvm);
>
> This function is not necessary, since the VM is disappearing anyway and
> the page tracker is not going to be called.

I think it is still necessary, as we are using srcu to protect the notifier, so
we should wait all the callers of notifier callbacks gone, i.e, synchronize_srcu()
is needed anyway.