From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Will Deacon <will@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-mm@kvack.org
Subject: [PATCH 2/3] mm: Allow arches to provide ptep_get()
Date: Mon, 15 Jun 2020 12:57:58 +0000 (UTC)
Message-ID: <087fa12b6e920e32315136b998aa834f99242695.1592225558.git.christophe.leroy@csgroup.eu> (raw)
In-Reply-To: <cover.1592225557.git.christophe.leroy@csgroup.eu>
Since commit 2ab3a0a02905 ("READ_ONCE: Enforce atomicity for
{READ,WRITE}_ONCE() memory accesses"), it is not possible anymore
to use READ_ONCE() to access complex page table entries like
the one defined for powerpc 8xx with 16k size pages.
Define a ptep_get() helper that architectures can override instead
of performing a READ_ONCE() on the page table entry pointer.
Fixes: 2ab3a0a02905 ("READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses")
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
include/asm-generic/hugetlb.h | 2 +-
include/linux/pgtable.h | 7 +++++++
mm/gup.c | 2 +-
3 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/include/asm-generic/hugetlb.h b/include/asm-generic/hugetlb.h
index 40f85decc2ee..8e1e6244a89d 100644
--- a/include/asm-generic/hugetlb.h
+++ b/include/asm-generic/hugetlb.h
@@ -122,7 +122,7 @@ static inline int huge_ptep_set_access_flags(struct vm_area_struct *vma,
#ifndef __HAVE_ARCH_HUGE_PTEP_GET
static inline pte_t huge_ptep_get(pte_t *ptep)
{
- return READ_ONCE(*ptep);
+ return ptep_get(ptep);
}
#endif
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 32b6c52d41b9..56c1e8eb7bb0 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -249,6 +249,13 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
}
#endif
+#ifndef __HAVE_ARCH_PTEP_GET
+static inline pte_t ptep_get(pte_t *ptep)
+{
+ return READ_ONCE(*ptep);
+}
+#endif
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
diff --git a/mm/gup.c b/mm/gup.c
index 761df4944ef5..6f47697f8fb0 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2196,7 +2196,7 @@ static inline pte_t gup_get_pte(pte_t *ptep)
*/
static inline pte_t gup_get_pte(pte_t *ptep)
{
- return READ_ONCE(*ptep);
+ return ptep_get(ptep);
}
#endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
--
2.25.0
next prev parent reply index
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-15 12:57 [PATCH 0/3] Fix build failure with v5.8-rc1 Christophe Leroy
2020-06-15 12:57 ` [PATCH 1/3] mm/gup: Use huge_ptep_get() in gup_hugepte() Christophe Leroy
2020-06-17 14:14 ` Michael Ellerman
2020-06-15 12:57 ` Christophe Leroy [this message]
2020-06-15 12:57 ` [PATCH 3/3] powerpc/8xx: Provide ptep_get() with 16k pages Christophe Leroy
2020-06-15 13:22 ` Peter Zijlstra
2020-06-17 14:21 ` Michael Ellerman
2020-06-17 14:38 ` Peter Zijlstra
2020-06-17 14:45 ` Christophe Leroy
2020-06-18 1:00 ` Michael Ellerman
2020-06-18 14:19 ` Christophe Leroy
2020-06-18 0:58 ` Michael Ellerman
2020-06-18 14:21 ` Christophe Leroy
2020-06-17 10:57 ` [PATCH 0/3] Fix build failure with v5.8-rc1 Will Deacon
2020-06-17 14:13 ` Michael Ellerman
2020-06-18 12:37 ` Michael Ellerman
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