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From:   Jia He <justin.he@arm.com>
To:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        James Morse <james.morse@arm.com>,
        Marc Zyngier <maz@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Cc:     Punit Agrawal <punitagrawal@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Morton <akpm@linux-foundation.org>, hejianet@gmail.com,
        Kaly Xin <Kaly.Xin@arm.com>, Jia He <justin.he@arm.com>
Subject: [PATCH v10 0/3] fix double page fault on arm64
Date:   Mon, 30 Sep 2019 09:57:37 +0800
Message-Id: <20190930015740.84362-1-justin.he@arm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

When we tested pmdk unit test vmmalloc_fork TEST1 in arm64 guest, there
will be a double page fault in __copy_from_user_inatomic of cow_user_page.

As told by Catalin: "On arm64 without hardware Access Flag, copying from
user will fail because the pte is old and cannot be marked young. So we
always end up with zeroed page after fork() + CoW for pfn mappings. we
don't always have a hardware-managed access flag on arm64."

Changes
v10:
    add r-b from Catalin and a-b from Kirill in PATCH 03
    remoe Reported-by in PATCH 01
v9: refactor cow_user_page for indention optimization (Catalin)
    hold the ptl longer (Catalin)
v8: change cow_user_page's return type (Matthew)
v7: s/pte_spinlock/pte_offset_map_lock (Kirill)
v6: fix error case of returning with spinlock taken (Catalin)
    move kmap_atomic to avoid handling kunmap_atomic
v5: handle the case correctly when !pte_same
    fix kbuild test failed
v4: introduce cpu_has_hw_af (Suzuki)
    bail out if !pte_same (Kirill)
v3: add vmf->ptl lock/unlock (Kirill A. Shutemov)
    add arch_faults_on_old_pte (Matthew, Catalin)
v2: remove FAULT_FLAG_WRITE when setting pte access flag (Catalin)

Jia He (3):
  arm64: cpufeature: introduce helper cpu_has_hw_af()
  arm64: mm: implement arch_faults_on_old_pte() on arm64
  mm: fix double page fault on arm64 if PTE_AF is cleared

 arch/arm64/include/asm/cpufeature.h | 10 +++
 arch/arm64/include/asm/pgtable.h    | 14 ++++
 mm/memory.c                         | 99 ++++++++++++++++++++++++-----
 3 files changed, 108 insertions(+), 15 deletions(-)

-- 
2.17.1