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    SubjectRe: [PATCH] KVM: x86/MMU: Zap non-leaf SPTEs when disabling dirty logging
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    On 5/26/22 16:30, Peter Xu wrote:
    > On Thu, May 26, 2022 at 02:01:43PM +0200, Paolo Bonzini wrote:
    >> On 5/26/22 01:09, Ben Gardon wrote:
    >>> + WARN_ON(max_mapping_level < iter.level);
    >>> +
    >>> + /*
    >>> + * If this page is already mapped at the highest
    >>> + * viable level, there's nothing more to do.
    >>> + */
    >>> + if (max_mapping_level == iter.level)
    >>> + continue;
    >>> +
    >>> + /*
    >>> + * The page can be remapped at a higher level, so step
    >>> + * up to zap the parent SPTE.
    >>> + */
    >>> + while (max_mapping_level > iter.level)
    >>> + tdp_iter_step_up(&iter);
    >>> +
    >>> /* Note, a successful atomic zap also does a remote TLB flush. */
    >>> - if (tdp_mmu_zap_spte_atomic(kvm, &iter))
    >>> - goto retry;
    >>> + tdp_mmu_zap_spte_atomic(kvm, &iter);
    >>> +
    >>
    >> Can you make this a sparate function (for example
    >> tdp_mmu_zap_collapsible_spte_atomic)? Otherwise looks great!
    >
    > There could be a tiny downside of using a helper in that it'll hide the
    > step-up of the iterator, which might not be as obvious as keeping it in the
    > loop?

    That's true, my reasoning is that zapping at a higher level can only be
    done by first moving the iterator up. Maybe
    tdp_mmu_zap_at_level_atomic() is a better Though, I can very well apply
    this patch as is.

    Paolo

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