Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1340296

Re: [PATCH v3 07/11] KVM: page track: add notifier support

Show all headers | View raw

On 02/19/2016 07:51 PM, Paolo Bonzini wrote:
>
>
> On 14/02/2016 12:31, Xiao Guangrong wrote:

>> +void kvm_page_track_write(struct kvm_vcpu *vcpu, gpa_t gpa, const u8 *new,
>> +			  int bytes)
>> +{
>> +	struct kvm_page_track_notifier_head *head;
>> +	struct kvm_page_track_notifier_node *n;
>> +	int idx;
>> +
>> +	head = &vcpu->kvm->arch.track_notifier_head;
>
> Please check outside SRCU if the notifier list is empty.  If so, there
> is no need to do the (relatively) expensive srcu_read_lock/unlock.
>

Good to me. I will check it by calling hlist_empty() first before holding
the srcu read lock.

> Paolo
>
>> +	idx = srcu_read_lock(&head->track_srcu);
>> +	hlist_for_each_entry_rcu(n, &head->track_notifier_list, node)
>> +		if (n->track_write)
>> +			n->track_write(vcpu, gpa, new, bytes);
>> +	srcu_read_unlock(&head->track_srcu, idx);
>> +}
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index e25ebb7..98019b6 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -4370,6 +4370,7 @@ int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
>>   	if (ret < 0)
>>   		return 0;
>
> A kvm_vcpu_mark_page_dirty is missing here, isn't it?  I can take care
> of it, but it would be great if you double-checked this.  If so, that
> should be fixed in stable kernels too.

No. It's already been handled in emulator_write_phys() -> kvm_vcpu_write_guest()
-> kvm_vcpu_write_guest_page() -> __kvm_write_guest_page().

>
> Can you add a kvm_vcpu_note_page_write(vcpu, gpa, val, bytes) function
> that takes care of calling kvm_vcpu_mark_page_dirty, kvm_mmu_pte_write
> and kvm_page_track-write?
>

After this patchset, kvm_mmu_pte_write is only a static notifier callback called
by kvm_page_track_write().

And the dirty tracking in emulator_write_phys() is handled in a public API (as my
explanation above), in emulator_cmpxchg_emulated is handled by itself. So i think
it is better to leaving dirty tracking to the separate paths, no? :)

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH v3 00/11] KVM: x86: track guest page access Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-02-14 12:50 +0100
  [PATCH v3 07/11] KVM: page track: add notifier support Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-02-14 12:50 +0100
    Re: [PATCH v3 07/11] KVM: page track: add notifier support Paolo Bonzini <pbonzini@redhat.com> - 2016-02-19 13:00 +0100
      Re: [PATCH v3 07/11] KVM: page track: add notifier support Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-02-23 05:50 +0100
        Re: [PATCH v3 07/11] KVM: page track: add notifier support Paolo Bonzini <pbonzini@redhat.com> - 2016-02-23 15:20 +0100
  [PATCH v3 04/11] KVM: page track: add the framework of guest page tracking Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-02-14 12:50 +0100
    Re: [PATCH v3 04/11] KVM: page track: add the framework of guest page  tracking Paolo Bonzini <pbonzini@redhat.com> - 2016-02-19 12:30 +0100
      Re: [PATCH v3 04/11] KVM: page track: add the framework of guest page  tracking Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-02-23 05:10 +0100
  [PATCH v3 03/11] KVM: MMU: introduce kvm_mmu_slot_gfn_write_protect Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-02-14 12:50 +0100
  Re: [PATCH v3 00/11] KVM: x86: track guest page access Paolo Bonzini <pbonzini@redhat.com> - 2016-02-19 13:10 +0100
    Re: [PATCH v3 00/11] KVM: x86: track guest page access Xiao Guangrong <guangrong.xiao@linux.intel.com> - 2016-02-22 11:20 +0100
      Re: [PATCH v3 00/11] KVM: x86: track guest page access Jike Song <jike.song@intel.com> - 2016-02-23 04:10 +0100
        RE: [PATCH v3 00/11] KVM: x86: track guest page access "Tian, Kevin" <kevin.tian@intel.com> - 2016-02-23 06:50 +0100
          Re: [PATCH v3 00/11] KVM: x86: track guest page access Paolo Bonzini <pbonzini@redhat.com> - 2016-02-23 13:20 +0100
        Re: [PATCH v3 00/11] KVM: x86: track guest page access Paolo Bonzini <pbonzini@redhat.com> - 2016-02-23 11:10 +0100
          Re: [PATCH v3 00/11] KVM: x86: track guest page access Jike Song <jike.song@intel.com> - 2016-02-23 13:00 +0100

csiph-web