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Message-Id: <20230522122429.1915021-2-mark.rutland@arm.com>
Date: Mon, 22 May 2023 13:24:04 +0100
From: Mark Rutland <mark.rutland@....com>
To: linux-kernel@...r.kernel.org
Cc: akiyks@...il.com, boqun.feng@...il.com, corbet@....net,
keescook@...omium.org, linux-arch@...r.kernel.org,
linux@...linux.org.uk, linux-doc@...r.kernel.org,
mark.rutland@....com, paulmck@...nel.org, peterz@...radead.org,
sstabellini@...nel.org, will@...nel.org
Subject: [PATCH 01/26] locking/atomic: arm: fix sync ops
The sync_*() ops on arch/arm are defined in terms of the regular bitops
with no special handling. This is not correct, as UP kernels elide
barriers for the fully-ordered operations, and so the required ordering
is lost when such UP kernels are run under a hypervsior on an SMP
system.
Fix this by defining sync ops with the required barriers.
Note: On 32-bit arm, the sync_*() ops are currently only used by Xen,
which requires ARMv7, but the semantics can be implemented for ARMv6+.
Fixes: e54d2f61528165bb ("xen/arm: sync_bitops")
Signed-off-by: Mark Rutland <mark.rutland@....com>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Russell King <linux@...linux.org.uk>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Cc: Will Deacon <will@...nel.org>
---
arch/arm/include/asm/assembler.h | 17 +++++++++++++++++
arch/arm/include/asm/sync_bitops.h | 29 +++++++++++++++++++++++++----
arch/arm/lib/bitops.h | 14 +++++++++++---
arch/arm/lib/testchangebit.S | 4 ++++
arch/arm/lib/testclearbit.S | 4 ++++
arch/arm/lib/testsetbit.S | 4 ++++
6 files changed, 65 insertions(+), 7 deletions(-)
diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 505a306e0271a..aebe2c8f6a686 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -394,6 +394,23 @@ ALT_UP_B(.L0_\@)
#endif
.endm
+/*
+ * Raw SMP data memory barrier
+ */
+ .macro __smp_dmb mode
+#if __LINUX_ARM_ARCH__ >= 7
+ .ifeqs "\mode","arm"
+ dmb ish
+ .else
+ W(dmb) ish
+ .endif
+#elif __LINUX_ARM_ARCH__ == 6
+ mcr p15, 0, r0, c7, c10, 5 @ dmb
+#else
+ .error "Incompatible SMP platform"
+#endif
+ .endm
+
#if defined(CONFIG_CPU_V7M)
/*
* setmode is used to assert to be in svc mode during boot. For v7-M
diff --git a/arch/arm/include/asm/sync_bitops.h b/arch/arm/include/asm/sync_bitops.h
index 6f5d627c44a3c..f46b3c570f92e 100644
--- a/arch/arm/include/asm/sync_bitops.h
+++ b/arch/arm/include/asm/sync_bitops.h
@@ -14,14 +14,35 @@
* ops which are SMP safe even on a UP kernel.
*/
+/*
+ * Unordered
+ */
+
#define sync_set_bit(nr, p) _set_bit(nr, p)
#define sync_clear_bit(nr, p) _clear_bit(nr, p)
#define sync_change_bit(nr, p) _change_bit(nr, p)
-#define sync_test_and_set_bit(nr, p) _test_and_set_bit(nr, p)
-#define sync_test_and_clear_bit(nr, p) _test_and_clear_bit(nr, p)
-#define sync_test_and_change_bit(nr, p) _test_and_change_bit(nr, p)
#define sync_test_bit(nr, addr) test_bit(nr, addr)
-#define arch_sync_cmpxchg arch_cmpxchg
+/*
+ * Fully ordered
+ */
+
+int _sync_test_and_set_bit(int nr, volatile unsigned long * p);
+#define sync_test_and_set_bit(nr, p) _sync_test_and_set_bit(nr, p)
+
+int _sync_test_and_clear_bit(int nr, volatile unsigned long * p);
+#define sync_test_and_clear_bit(nr, p) _sync_test_and_clear_bit(nr, p)
+
+int _sync_test_and_change_bit(int nr, volatile unsigned long * p);
+#define sync_test_and_change_bit(nr, p) _sync_test_and_change_bit(nr, p)
+
+#define arch_sync_cmpxchg(ptr, old, new) \
+({ \
+ __typeof__(*(ptr)) __ret; \
+ __smp_mb__before_atomic(); \
+ __ret = arch_cmpxchg_relaxed((ptr), (old), (new)); \
+ __smp_mb__after_atomic(); \
+ __ret; \
+})
#endif
diff --git a/arch/arm/lib/bitops.h b/arch/arm/lib/bitops.h
index 95bd359912889..f069d1b2318e6 100644
--- a/arch/arm/lib/bitops.h
+++ b/arch/arm/lib/bitops.h
@@ -28,7 +28,7 @@ UNWIND( .fnend )
ENDPROC(\name )
.endm
- .macro testop, name, instr, store
+ .macro __testop, name, instr, store, barrier
ENTRY( \name )
UNWIND( .fnstart )
ands ip, r1, #3
@@ -38,7 +38,7 @@ UNWIND( .fnstart )
mov r0, r0, lsr #5
add r1, r1, r0, lsl #2 @ Get word offset
mov r3, r2, lsl r3 @ create mask
- smp_dmb
+ \barrier
#if __LINUX_ARM_ARCH__ >= 7 && defined(CONFIG_SMP)
.arch_extension mp
ALT_SMP(W(pldw) [r1])
@@ -50,13 +50,21 @@ UNWIND( .fnstart )
strex ip, r2, [r1]
cmp ip, #0
bne 1b
- smp_dmb
+ \barrier
cmp r0, #0
movne r0, #1
2: bx lr
UNWIND( .fnend )
ENDPROC(\name )
.endm
+
+ .macro testop, name, instr, store
+ __testop \name, \instr, \store, smp_dmb
+ .endm
+
+ .macro sync_testop, name, instr, store
+ __testop \name, \instr, \store, __smp_dmb
+ .endm
#else
.macro bitop, name, instr
ENTRY( \name )
diff --git a/arch/arm/lib/testchangebit.S b/arch/arm/lib/testchangebit.S
index 4ebecc67e6e04..f13fe9bc2399a 100644
--- a/arch/arm/lib/testchangebit.S
+++ b/arch/arm/lib/testchangebit.S
@@ -10,3 +10,7 @@
.text
testop _test_and_change_bit, eor, str
+
+#if __LINUX_ARM_ARCH__ >= 6
+sync_testop _sync_test_and_change_bit, eor, str
+#endif
diff --git a/arch/arm/lib/testclearbit.S b/arch/arm/lib/testclearbit.S
index 009afa0f5b4a7..4d2c5ca620ebf 100644
--- a/arch/arm/lib/testclearbit.S
+++ b/arch/arm/lib/testclearbit.S
@@ -10,3 +10,7 @@
.text
testop _test_and_clear_bit, bicne, strne
+
+#if __LINUX_ARM_ARCH__ >= 6
+sync_testop _sync_test_and_clear_bit, bicne, strne
+#endif
diff --git a/arch/arm/lib/testsetbit.S b/arch/arm/lib/testsetbit.S
index f3192e55acc87..649dbab65d8d0 100644
--- a/arch/arm/lib/testsetbit.S
+++ b/arch/arm/lib/testsetbit.S
@@ -10,3 +10,7 @@
.text
testop _test_and_set_bit, orreq, streq
+
+#if __LINUX_ARM_ARCH__ >= 6
+sync_testop _sync_test_and_set_bit, orreq, streq
+#endif
--
2.30.2
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