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    SubjectRe: [PATCH v3 0/9] Fixup page directory freeing
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    On 1/14/20 4:20 PM, Peter Zijlstra wrote:
    > On Tue, Jan 14, 2020 at 03:31:36PM +0530, Aneesh Kumar K.V wrote:
    >> This is a repost of patch series from Peter with the arch specific changes except ppc64 dropped.
    >> ppc64 changes are added here because we are redoing the patch series on top of ppc64 changes. This makes it
    >> easy to backport these changes. Only the first 3 patches need to be backported to stable.
    >>
    >> The thing is, on anything SMP, freeing page directories should observe the
    >> exact same order as normal page freeing:
    >>
    >> 1) unhook page/directory
    >> 2) TLB invalidate
    >> 3) free page/directory
    >>
    >> Without this, any concurrent page-table walk could end up with a Use-after-Free.
    >> This is esp. trivial for anything that has software page-table walkers
    >> (HAVE_FAST_GUP / software TLB fill) or the hardware caches partial page-walks
    >> (ie. caches page directories).
    >>
    >> Even on UP this might give issues since mmu_gather is preemptible these days.
    >> An interrupt or preempted task accessing user pages might stumble into the free
    >> page if the hardware caches page directories.
    >>
    >> This patch series fixup ppc64 and add generic MMU_GATHER changes to support the conversion of other architectures.
    >> I haven't added patches w.r.t other architecture because they are yet to be acked.
    >
    > Obviously looks good to me; will you route this through the Power tree
    > since you're in a hurry to see this fixed?
    >

    Michael,

    Can you take this via your tree?

    -aneesh

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