linux-kernel - Re: [PATCH V2 1/2] mm/autonuma: Let architecture override how the write bit should be stashed in a protnone pte.

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Date:   Tue, 14 Feb 2017 16:20:08 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Michael Ellerman <michaele@....ibm.com>
Cc:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Rik van Riel <riel@...riel.com>,
        Mel Gorman <mgorman@...hsingularity.net>, paulus@...abs.org,
        benh@...nel.crashing.org, linux-mm@...ck.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/2] mm/autonuma: Let architecture override how the
 write bit should be stashed in a protnone pte.

On Tue, 14 Feb 2017 21:59:23 +1100 Michael Ellerman <michaele@....ibm.com> wrote:

> "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> writes:
> 
> > On Tuesday 14 February 2017 11:19 AM, Michael Ellerman wrote:
> >> "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> writes:
> >>
> >>> Autonuma preserves the write permission across numa fault to avoid taking
> >>> a writefault after a numa fault (Commit: b191f9b106ea " mm: numa: preserve PTE
> >>> write permissions across a NUMA hinting fault"). Architecture can implement
> >>> protnone in different ways and some may choose to implement that by clearing Read/
> >>> Write/Exec bit of pte. Setting the write bit on such pte can result in wrong
> >>> behaviour. Fix this up by allowing arch to override how to save the write bit
> >>> on a protnone pte.
> >> This is pretty obviously a nop on arches that don't implement the new
> >> hooks, but it'd still be good to get an ack from someone in mm land
> >> before I merge it.
> >
> >
> > To get it apply cleanly you may need
> > http://ozlabs.org/~akpm/mmots/broken-out/mm-autonuma-dont-use-set_pte_at-when-updating-protnone-ptes.patch
> > http://ozlabs.org/~akpm/mmots/broken-out/mm-autonuma-dont-use-set_pte_at-when-updating-protnone-ptes-fix.patch
> 
> Ah OK, I missed those.
> 
> In that case these two should probably go via Andrew's tree.

Done.  But
mm-autonuma-dont-use-set_pte_at-when-updating-protnone-ptes.patch is on
hold because Aneesh saw a testing issue, so these two are also on hold.