linux-kernel - [PATCH 0/2] Create 'old' ptes for faultaround mappings on arm64 with hardware access flag

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Date:   Wed,  9 Dec 2020 16:39:48 +0000
From:   Will Deacon <will@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Jan Kara <jack@...e.cz>, Minchan Kim <minchan@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Vinayak Menon <vinmenon@...eaurora.org>,
        kernel-team@...roid.com
Subject: [PATCH 0/2] Create 'old' ptes for faultaround mappings on arm64 with hardware access flag

Hi folks,

This series allows architectures to opt-in at runtime for faultaround
mappings to be created as 'old' instead of 'young'. Although there have
been previous attempts at this, they failed either because the decision
was deferred to userspace [1] or because it was done unconditionally and
shown to regress benchmarks for particular architectures [2].

Since this patch has demonstrated considerable benefits for arm64-based
Android devices with hardware access flag capabilities, patch two enables
this functionality there.

Cheers,

Will

[1] https://www.spinics.net/lists/linux-mm/msg143831.html
[2] 315d09bf30c2 ("Revert "mm: make faultaround produce old ptes"")

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Jan Kara <jack@...e.cz>
Cc: Minchan Kim <minchan@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Vinayak Menon <vinmenon@...eaurora.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: <kernel-team@...roid.com>

--->8

Will Deacon (2):
  mm: Allow architectures to request 'old' entries when prefaulting
  arm64: mm: Implement arch_wants_old_faultaround_pte()

 arch/arm64/include/asm/cpufeature.h | 12 +++++++++++
 arch/arm64/include/asm/pgtable.h    |  8 +++++++-
 include/linux/mm.h                  |  5 ++++-
 mm/memory.c                         | 31 ++++++++++++++++++++++++++---
 4 files changed, 51 insertions(+), 5 deletions(-)

-- 
2.29.2.576.ga3fc446d84-goog