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    SubjectRe: [PATCH 7/8] membarrier: Remove arm (32) support for SYNC_CORE
    On Tue, Jun 15, 2021 at 08:21:12PM -0700, Andy Lutomirski wrote:
    > On arm32, the only way to safely flush icache from usermode is to call
    > cacheflush(2). This also handles any required pipeline flushes, so
    > membarrier's SYNC_CORE feature is useless on arm. Remove it.

    So SYNC_CORE is there to help an architecture that needs to do something
    per CPU. If I$ invalidation is broadcast and I$ invalidation also
    triggers the flush of any uarch caches derived from it (if there are
    any).

    Now arm_syscall() NR(cacheflush) seems to do flush_icache_user_range(),
    which, if I read things right, end up in arch/arm/mm/*.S, but that
    doesn't consider cache_ops_need_broadcast().

    Will suggests that perhaps ARM 11MPCore might need this due to their I$
    flush maybe not being broadcast

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