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    SubjectRe: [patch -mm 1/2] i386: add ptep_test_and_clear_{dirty,young}
    On Sun, 25 Mar 2007, Zachary Amsden wrote:

    > If you actually clear the bit, you need to:
    >
    > + pte_update_defer(vma->vm_mm, addr, ptep);
    >
    > The reason is, when updating PTEs, the hypervisor must be notified. Using
    > atomic operations to do this is fine for all hypervisors I am aware of.
    > However, for hypervisors which shadow page tables, if these PTE modifications
    > are not trapped, you need a post-modification call to fulfill the update of
    > the shadow page table.
    >

    Then why was ptep_test_and_clear_{dirty,young} ever removed in the first
    place?? To gain the optimization of one fewer branch and introduce a hack
    to advertise it's existance so the generic header file doesn't include its
    own version?
    -
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