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    Subject[patch 0/7] x86, cpa: cpa related changes to be inline with TLB Application note - v2
    TLB Application note[1] says:

    "The TLBs may contain both ordinary and large-page translations for a 4-KByte
    range of linear addresses. This may occur if software modifies the paging
    structures so that the page size used for the address range changes. If the
    two translations differ with respect to page frame or attributes (e.g.,
    permissions), processor behavior is undefined and may be implementation
    specific. The processor may use a page frame or attributes that correspond to
    neither translation; it may improperly set or fail to set the dirty bit in the
    appropriate paging-structure entry.

    Such undefined behavior is problematic because prefetches and memory accesses
    that are a result of speculative execution may occur, using the affected range
    of linear addresses. It is also problematic if software (including the software
    modifying the paging structures) is accessing data or executing code in the
    affected range of linear addresses. Software should not write to a
    paging-structure entry in a way that would change, for any linear address,
    both the page size and either the page frame or attributes."

    Currently we violate this at:

    a. kernel identity mapping, where large/small pages setup very early in the
    boot will be split up/merged into large pages along with attribute changes
    during the direct memory mapping init.

    b. while doing cpa(), potentially we will split large page and change attribute
    both at the same time.

    Following patches fixes this behavior.


    Signed-off-by: Suresh Siddha <>
    1. Fix the deadlock associated with smp call function and spin_lock_irqsave()
    for pgd_lock.
    2. No alias checks for __set_pages_np()/__set_pages_p() avoiding the large
    text page split from atomic context in CONFIG_DEBUG_PAGEALLOC.
    3. Serialize cpa() for !CONFIG_DEBUG_PAGEALLOC, so that a cpu with stale
    large page tlb's(but small PTE's in memory) won't do a cpa() in parallel
    to some other cpu splitting large pages and changing page attribute for
    a small page.

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