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Subject: Re: [RFC][PATCH 1/5] mm: Rework {set,clear,mm}_tlb_flush_pending()
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Peter Zijlstra <peterz@infradead.org>,
        Will Deacon <will.deacon@arm.com>
Cc: torvalds@linux-foundation.org, oleg@redhat.com,
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        linux-kernel@vger.kernel.org, mingo@kernel.org,
        stern@rowland.harvard.edu, Mel Gorman <mgorman@suse.de>,
        Rik van Riel <riel@redhat.com>
Date: Wed, 02 Aug 2017 11:23:12 +1000
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On Wed, 2017-08-02 at 00:59 +0200, Peter Zijlstra wrote:
> > PowerPC for example uses PTESYNC before the TBLIE, so does a SYNC after
> > work? Ben?
> > From what I gather it is not. You have TLBSYNC for it. So the good news

tlbsync is pretty much a nop these days. ptesync is a strict superset
of sync and we have it after every tlbie.

> is that PPC-radix does all that and is fully serialized on the tlb
> flush. Not sure for the PPC-hash case.
> 
> At the same time, smp_mb() is not sufficient on ARM either, they need a
> DSB barrier on both ends.
> 
> So are we going to mandate tlb flush implementations are completely
> ordered ?

Cheers,
Ben.