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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,
	Suzuki Poulose <Suzuki.Poulose@arm.com>
Cc: "Punit Agrawal" <punitagrawal@gmail.com>,
	"Anshuman Khandual" <anshuman.khandual@arm.com>,
	"Jun Yao" <yaojun8558363@gmail.com>,
	"Alex Van Brunt" <avanbrunt@nvidia.com>,
	"Robin Murphy" <robin.murphy@arm.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Ralph Campbell" <rcampbell@nvidia.com>,
	hejianet@gmail.com, "Kaly Xin" <Kaly.Xin@arm.com>,
	"Jia He" <justin.he@arm.com>
Subject: [PATCH v4 2/3] arm64: mm: implement arch_faults_on_old_pte() on arm64
Date: Wed, 18 Sep 2019 21:19:13 +0800	[thread overview]
Message-ID: <20190918131914.38081-3-justin.he@arm.com> (raw)
In-Reply-To: <20190918131914.38081-1-justin.he@arm.com>

On arm64 without hardware Access Flag, copying fromuser 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.

Hence implement arch_faults_on_old_pte on arm64 to indicate that it might
cause page fault when accessing old pte.

Signed-off-by: Jia He <justin.he@arm.com>
---
 arch/arm64/include/asm/pgtable.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index e09760ece844..4a9939615e41 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -868,6 +868,18 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
 #define phys_to_ttbr(addr)	(addr)
 #endif
 
+/*
+ * On arm64 without hardware Access Flag, copying fromuser 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.
+ */
+static inline bool arch_faults_on_old_pte(void)
+{
+	return !cpu_has_hw_af();
+}
+#define arch_faults_on_old_pte arch_faults_on_old_pte
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_PGTABLE_H */
-- 
2.17.1


  parent reply	other threads:[~2019-09-18 13:19 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-18 13:19 [PATCH v4 0/3] fix double page fault on arm64 Jia He
2019-09-18 13:19 ` [PATCH v4 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af() Jia He
2019-09-18 14:20   ` Matthew Wilcox
2019-09-18 16:49     ` Catalin Marinas
2019-09-18 14:20   ` Suzuki K Poulose
2019-09-18 16:45     ` Catalin Marinas
2019-09-19  1:55       ` Justin He (Arm Technology China)
2019-09-18 13:19 ` Jia He [this message]
2019-09-18 13:19 ` [PATCH v4 3/3] mm: fix double page fault on arm64 if PTE_AF is cleared Jia He
2019-09-18 14:00   ` Kirill A. Shutemov
2019-09-18 18:00     ` Catalin Marinas
2019-09-19 15:00       ` Kirill A. Shutemov
2019-09-19 15:41         ` Catalin Marinas
2019-09-19 15:51           ` Kirill A. Shutemov
2019-09-19  2:16     ` Jia He
2019-09-19 14:57       ` Kirill A. Shutemov
2019-09-19 15:02         ` Justin He (Arm Technology China)
2019-09-18 19:35   ` kbuild test robot
2019-09-19  1:46     ` Justin He (Arm Technology China)

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