Re: [PATCH V2 1/2] mm/autonuma: Let architecture override how the write bit should be stashed in a protnone pte.
From: Aneesh Kumar K.V <hidden>
Date: 2017-02-14 05:56:05
Also in:
linux-mm, lkml
On Tuesday 14 February 2017 11:19 AM, Michael Ellerman wrote:
"Aneesh Kumar K.V" [off-list ref] writes:quoted
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