Re: [PATCH -mm v8 5/7] mmu-notifier: add clear_young callback

[Paolo Bonzini <pbonzini@redhat.com>]

On 15/07/2015 21:16, Andres Lagar-Cavilla wrote:
>> > +static int kvm_mmu_notifier_clear_young(struct mmu_notifier *mn,
>> > +                                       struct mm_struct *mm,
>> > +                                       unsigned long start,
>> > +                                       unsigned long end)
>> > +{
>> > +       struct kvm *kvm = mmu_notifier_to_kvm(mn);
>> > +       int young, idx;
> For reclaim, the clear_flush_young notifier may blow up the secondary
> pte to estimate the access pattern, depending on hardware support (EPT
> access bits available in Haswell onwards, not sure about AMD, PPC,
> etc).

It seems like this problem is limited to pre-Haswell EPT.

I'm okay with the patch.  If we find problems later we can always add a
parameter to kvm_age_hva so that it effectively doesn't do anything on
clear_young.

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo

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