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    SubjectRe: [PATCH 2/4] KVM: Avoid checking huge page mappings in get_dirty_log()
    Marcelo Tosatti <mtosatti@redhat.com> wrote:

    >
    > This is a race with hugetlbfs which is not an issue ATM (it is
    > hidden by the removal of huge sptes in get_dirty).

    Thank you!
    I did not notice this possibility at all.

    ...

    > It can be fixed with a preceding patch that checks whether
    > slot->dirty_bitmap value changes between mapping_level and after
    > mmu_lock acquision, similarly to mmu_seq. Also please add a
    > WARN_ON in mmu_set_spte if(slot->dirty_bitmap && level > 1).
    > And document it clearly.

    We may also be able to change the "if (slot->dirty_bitmap)" check to
    use another flag so that we can delay the start of logging until
    mmu_lock acquisition in kvm_set_memory_region().

    Looking dirty_bitmap directly should be limited to when we are in
    get_dirty functions.

    Takuya


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