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SubjectRe: [PATCH 18/22] kvm: mmu: Support disabling dirty logging for the tdp MMU
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On 07/10/20 18:30, Ben Gardon wrote:
>> I'm starting to wonder if another iterator like
>> for_each_tdp_leaf_pte_root would be clearer, since this idiom repeats
>> itself quite often. The tdp_iter_next_leaf function would be easily
>> implemented as
>>
>> while (likely(iter->valid) &&
>> (!is_shadow_present_pte(iter.old_spte) ||
>> is_last_spte(iter.old_spte, iter.level))
>> tdp_iter_next(iter);
> Do you see a substantial efficiency difference between adding a
> tdp_iter_next_leaf and building on for_each_tdp_pte_using_root with
> something like:
>
> #define for_each_tdp_leaf_pte_using_root(_iter, _root, _start, _end) \
> for_each_tdp_pte_using_root(_iter, _root, _start, _end) \
> if (!is_shadow_present_pte(_iter.old_spte) || \
> !is_last_spte(_iter.old_spte, _iter.level)) \
> continue; \
> else
>
> I agree that putting those checks in a wrapper makes the code more concise.
>

No, that would be just another way to write the same thing. That said,
making the iteration API more complicated also has disadvantages because
if get a Cartesian explosion of changes.

Regarding the naming, I'm leaning towards

tdp_root_for_each_pte
tdp_vcpu_for_each_pte

which is shorter than the version with "using" and still clarifies that
"root" and "vcpu" are the thing that the iteration works on.

Paolo

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