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

[Aneesh Kumar K.V]

On Tuesday 14 February 2017 11:19 AM, Michael Ellerman wrote:
> "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> 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

They are strictly not needed after the saved write patch. But I didn't 
request to drop them, because the patch helps us
to get closer to the goal of no ste_pte_at() call on present ptes.

-aneesh