Messages in this thread | | | Date | Wed, 16 Jun 2021 12:16:27 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 7/8] membarrier: Remove arm (32) support for SYNC_CORE |
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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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