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

On 15/07/2015 21:16, Andres Lagar-Cavilla wrote:

quoted

quoted

+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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