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

Aneesh Kumar K.V aneesh.kumar at linux.vnet.ibm.com
Tue Feb 14 16:55:48 AEDT 2017

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

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.


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