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>,
"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, "Jia He" <justin.he@arm.com>
Subject: [PATCH v3 1/2] arm64: mm: implement arch_faults_on_old_pte() on arm64
Date: Sat, 14 Sep 2019 00:32:38 +0800 [thread overview]
Message-ID: <20190913163239.125108-2-justin.he@arm.com> (raw)
In-Reply-To: <20190913163239.125108-1-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..b41399d758df 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 true;
+}
+#define arch_faults_on_old_pte arch_faults_on_old_pte
+
#endif /* !__ASSEMBLY__ */
#endif /* __ASM_PGTABLE_H */
--
2.17.1
next prev parent reply other threads:[~2019-09-13 16:32 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-13 16:32 [PATCH v3 0/2] fix double page fault on arm64 Jia He
2019-09-13 16:32 ` Jia He [this message]
2019-09-16 9:20 ` [PATCH v3 1/2] arm64: mm: implement arch_faults_on_old_pte() " Kirill A. Shutemov
2019-09-13 16:32 ` [PATCH v3 2/2] mm: fix double page fault on arm64 if PTE_AF is cleared Jia He
2019-09-16 9:16 ` Kirill A. Shutemov
2019-09-16 9:35 ` Justin He (Arm Technology China)
2019-09-16 14:16 ` Kirill A. Shutemov
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