[PATCH v2 0/4] riscv: Add Zalasr ISA extension support

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* [PATCH v2 0/4] riscv: Add Zalasr ISA extension support
@ 2025-09-02  4:24 Xu Lu
  2025-09-02  4:24 ` [PATCH v2 1/4] riscv: add ISA extension parsing for Zalasr Xu Lu
                   ` (4 more replies)
  0 siblings, 5 replies; 9+ messages in thread
From: Xu Lu @ 2025-09-02  4:24 UTC (permalink / raw)
  To: robh, krzk+dt, conor+dt, paul.walmsley, palmer, aou, alex, ajones,
	brs
  Cc: devicetree, linux-riscv, linux-kernel, apw, joe, Xu Lu

This patch adds support for the Zalasr ISA extension, which supplies the
real load acquire/store release instructions.

The specification can be found here:
https://github.com/riscv/riscv-zalasr/blob/main/chapter2.adoc

This patch seires has been tested with ltp on Qemu with Brensan's zalasr
support patch[1].

Some false positive spacing error happens during patch checking. Thus I
CCed maintainers of checkpatch.pl as well.

[1] https://lore.kernel.org/all/CAGPSXwJEdtqW=nx71oufZp64nK6tK=0rytVEcz4F-gfvCOXk2w@mail.gmail.com/

v2:
 - Adjust the order of Zalasr and Zalrsc in dt-bindings. Thanks to 
Conor.

Xu Lu (4):
  riscv: add ISA extension parsing for Zalasr
  dt-bindings: riscv: Add Zalasr ISA extension description
  riscv: Instroduce Zalasr instructions
  riscv: Use Zalasr for smp_load_acquire/smp_store_release

 .../devicetree/bindings/riscv/extensions.yaml |  5 ++
 arch/riscv/include/asm/barrier.h              | 79 ++++++++++++++++---
 arch/riscv/include/asm/hwcap.h                |  1 +
 arch/riscv/include/asm/insn-def.h             | 79 +++++++++++++++++++
 arch/riscv/kernel/cpufeature.c                |  1 +
 5 files changed, 154 insertions(+), 11 deletions(-)

-- 
2.20.1


^ permalink raw reply	[flat|nested] 9+ messages in thread

* [PATCH v2 1/4] riscv: add ISA extension parsing for Zalasr
  2025-09-02  4:24 [PATCH v2 0/4] riscv: Add Zalasr ISA extension support Xu Lu
@ 2025-09-02  4:24 ` Xu Lu
  2025-09-02  4:24 ` [PATCH v2 2/4] dt-bindings: riscv: Add Zalasr ISA extension description Xu Lu
                   ` (3 subsequent siblings)
  4 siblings, 0 replies; 9+ messages in thread
From: Xu Lu @ 2025-09-02  4:24 UTC (permalink / raw)
  To: robh, krzk+dt, conor+dt, paul.walmsley, palmer, aou, alex, ajones,
	brs
  Cc: devicetree, linux-riscv, linux-kernel, apw, joe, Xu Lu

Add parsing for Zalasr ISA extension.

Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
---
 arch/riscv/include/asm/hwcap.h | 1 +
 arch/riscv/kernel/cpufeature.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index affd63e11b0a3..ae3852c4f2ca2 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -106,6 +106,7 @@
 #define RISCV_ISA_EXT_ZAAMO		97
 #define RISCV_ISA_EXT_ZALRSC		98
 #define RISCV_ISA_EXT_ZICBOP		99
+#define RISCV_ISA_EXT_ZALASR		100
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 743d53415572e..bf9d3d92bf372 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -472,6 +472,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_DATA(zaamo, RISCV_ISA_EXT_ZAAMO),
 	__RISCV_ISA_EXT_DATA(zabha, RISCV_ISA_EXT_ZABHA),
 	__RISCV_ISA_EXT_DATA(zacas, RISCV_ISA_EXT_ZACAS),
+	__RISCV_ISA_EXT_DATA(zalasr, RISCV_ISA_EXT_ZALASR),
 	__RISCV_ISA_EXT_DATA(zalrsc, RISCV_ISA_EXT_ZALRSC),
 	__RISCV_ISA_EXT_DATA(zawrs, RISCV_ISA_EXT_ZAWRS),
 	__RISCV_ISA_EXT_DATA(zfa, RISCV_ISA_EXT_ZFA),
-- 
2.20.1


^ permalink raw reply related	[flat|nested] 9+ messages in thread

* [PATCH v2 2/4] dt-bindings: riscv: Add Zalasr ISA extension description
  2025-09-02  4:24 [PATCH v2 0/4] riscv: Add Zalasr ISA extension support Xu Lu
  2025-09-02  4:24 ` [PATCH v2 1/4] riscv: add ISA extension parsing for Zalasr Xu Lu
@ 2025-09-02  4:24 ` Xu Lu
  2025-09-02 19:46   ` Conor Dooley
  2025-09-02  4:24 ` [PATCH v2 3/4] riscv: Instroduce Zalasr instructions Xu Lu
                   ` (2 subsequent siblings)
  4 siblings, 1 reply; 9+ messages in thread
From: Xu Lu @ 2025-09-02  4:24 UTC (permalink / raw)
  To: robh, krzk+dt, conor+dt, paul.walmsley, palmer, aou, alex, ajones,
	brs
  Cc: devicetree, linux-riscv, linux-kernel, apw, joe, Xu Lu

Add description for the Zalasr ISA extension

Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
---
 Documentation/devicetree/bindings/riscv/extensions.yaml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml
index ede6a58ccf534..100fe53fb0731 100644
--- a/Documentation/devicetree/bindings/riscv/extensions.yaml
+++ b/Documentation/devicetree/bindings/riscv/extensions.yaml
@@ -242,6 +242,11 @@ properties:
             is supported as ratified at commit 5059e0ca641c ("update to
             ratified") of the riscv-zacas.
 
+        - const: zalasr
+          description: |
+            The standard Zalasr extension for load-acquire/store-release as frozen
+            at commit 194f0094 ("Version 0.9 for freeze") of riscv-zalasr.
+
         - const: zalrsc
           description: |
             The standard Zalrsc extension for load-reserved/store-conditional as
-- 
2.20.1


^ permalink raw reply related	[flat|nested] 9+ messages in thread

* Re: [PATCH v2 2/4] dt-bindings: riscv: Add Zalasr ISA extension description
  2025-09-02  4:24 ` [PATCH v2 2/4] dt-bindings: riscv: Add Zalasr ISA extension description Xu Lu
@ 2025-09-02 19:46   ` Conor Dooley
  0 siblings, 0 replies; 9+ messages in thread
From: Conor Dooley @ 2025-09-02 19:46 UTC (permalink / raw)
  To: Xu Lu
  Cc: robh, krzk+dt, conor+dt, paul.walmsley, palmer, aou, alex, ajones,
	brs, devicetree, linux-riscv, linux-kernel, apw, joe

[-- Attachment #1: Type: text/plain, Size: 215 bytes --]

On Tue, Sep 02, 2025 at 12:24:30PM +0800, Xu Lu wrote:
> Add description for the Zalasr ISA extension
> 
> Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>

Acked-by: Conor Dooley <conor.dooley@microchip.com>

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

^ permalink raw reply	[flat|nested] 9+ messages in thread

* [PATCH v2 3/4] riscv: Instroduce Zalasr instructions
  2025-09-02  4:24 [PATCH v2 0/4] riscv: Add Zalasr ISA extension support Xu Lu
  2025-09-02  4:24 ` [PATCH v2 1/4] riscv: add ISA extension parsing for Zalasr Xu Lu
  2025-09-02  4:24 ` [PATCH v2 2/4] dt-bindings: riscv: Add Zalasr ISA extension description Xu Lu
@ 2025-09-02  4:24 ` Xu Lu
  2025-09-02  4:24 ` [PATCH v2 4/4] riscv: Use Zalasr for smp_load_acquire/smp_store_release Xu Lu
  2025-09-02 16:59 ` [PATCH v2 0/4] riscv: Add Zalasr ISA extension support Andrea Parri
  4 siblings, 0 replies; 9+ messages in thread
From: Xu Lu @ 2025-09-02  4:24 UTC (permalink / raw)
  To: robh, krzk+dt, conor+dt, paul.walmsley, palmer, aou, alex, ajones,
	brs
  Cc: devicetree, linux-riscv, linux-kernel, apw, joe, Xu Lu

Introduce l{b|h|w|d}.{aq|aqrl} and s{b|h|w|d}.{rl|aqrl} instruction
encodings.

Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
---
 arch/riscv/include/asm/insn-def.h | 79 +++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

diff --git a/arch/riscv/include/asm/insn-def.h b/arch/riscv/include/asm/insn-def.h
index d5adbaec1d010..3fec7e66ce50f 100644
--- a/arch/riscv/include/asm/insn-def.h
+++ b/arch/riscv/include/asm/insn-def.h
@@ -179,6 +179,7 @@
 #define RV___RS1(v)		__RV_REG(v)
 #define RV___RS2(v)		__RV_REG(v)
 
+#define RV_OPCODE_AMO		RV_OPCODE(47)
 #define RV_OPCODE_MISC_MEM	RV_OPCODE(15)
 #define RV_OPCODE_OP_IMM	RV_OPCODE(19)
 #define RV_OPCODE_SYSTEM	RV_OPCODE(115)
@@ -208,6 +209,84 @@
 	__ASM_STR(.error "hlv.d requires 64-bit support")
 #endif
 
+#define LB_AQ(dest, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(0), FUNC7(26),			\
+	       RD(dest), RS1(addr), __RS2(0))
+
+#define LB_AQRL(dest, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(0), FUNC7(27),			\
+	       RD(dest), RS1(addr), __RS2(0))
+
+#define LH_AQ(dest, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(1), FUNC7(26),			\
+	       RD(dest), RS1(addr), __RS2(0))
+
+#define LH_AQRL(dest, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(1), FUNC7(27),			\
+	       RD(dest), RS1(addr), __RS2(0))
+
+#define LW_AQ(dest, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(2), FUNC7(26),			\
+	       RD(dest), RS1(addr), __RS2(0))
+
+#define LW_AQRL(dest, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(2), FUNC7(27),			\
+	       RD(dest), RS1(addr), __RS2(0))
+
+#define SB_RL(src, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(0), FUNC7(29),			\
+	       __RD(0), RS1(addr), RS2(src))
+
+#define SB_AQRL(src, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(0), FUNC7(31),			\
+	       __RD(0), RS1(addr), RS2(src))
+
+#define SH_RL(src, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(1), FUNC7(29),			\
+	       __RD(0), RS1(addr), RS2(src))
+
+#define SH_AQRL(src, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(1), FUNC7(31),			\
+	       __RD(0), RS1(addr), RS2(src))
+
+#define SW_RL(src, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(2), FUNC7(29),			\
+	       __RD(0), RS1(addr), RS2(src))
+
+#define SW_AQRL(src, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(2), FUNC7(31),			\
+	       __RD(0), RS1(addr), RS2(src))
+
+#ifdef CONFIG_64BIT
+#define LD_AQ(dest, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(3), FUNC7(26),			\
+	       RD(dest), RS1(addr), __RS2(0))
+
+#define LD_AQRL(dest, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(3), FUNC7(27),			\
+	       RD(dest), RS1(addr), __RS2(0))
+
+#define SD_RL(src, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(3), FUNC7(29),			\
+	       __RD(0), RS1(addr), RS2(src))
+
+#define SD_AQRL(src, addr)					\
+	INSN_R(OPCODE_AMO, FUNC3(3), FUNC7(31),			\
+	       __RD(0), RS1(addr), RS2(src))
+#else
+#define LD_AQ(dest, addr)					\
+	__ASM_STR(.error "ld.aq requires 64-bit support")
+
+#define LD_AQRL(dest, addr)					\
+	__ASM_STR(.error "ld.aqrl requires 64-bit support")
+
+#define SD_RL(dest, addr)					\
+	__ASM_STR(.error "sd.rl requires 64-bit support")
+
+#define SD_AQRL(dest, addr)					\
+	__ASM_STR(.error "sd.aqrl requires 64-bit support")
+#endif
+
 #define SINVAL_VMA(vaddr, asid)					\
 	INSN_R(OPCODE_SYSTEM, FUNC3(0), FUNC7(11),		\
 	       __RD(0), RS1(vaddr), RS2(asid))
-- 
2.20.1


^ permalink raw reply related	[flat|nested] 9+ messages in thread

* [PATCH v2 4/4] riscv: Use Zalasr for smp_load_acquire/smp_store_release
  2025-09-02  4:24 [PATCH v2 0/4] riscv: Add Zalasr ISA extension support Xu Lu
                   ` (2 preceding siblings ...)
  2025-09-02  4:24 ` [PATCH v2 3/4] riscv: Instroduce Zalasr instructions Xu Lu
@ 2025-09-02  4:24 ` Xu Lu
  2025-09-03  1:06   ` kernel test robot
  2025-09-02 16:59 ` [PATCH v2 0/4] riscv: Add Zalasr ISA extension support Andrea Parri
  4 siblings, 1 reply; 9+ messages in thread
From: Xu Lu @ 2025-09-02  4:24 UTC (permalink / raw)
  To: robh, krzk+dt, conor+dt, paul.walmsley, palmer, aou, alex, ajones,
	brs
  Cc: devicetree, linux-riscv, linux-kernel, apw, joe, Xu Lu

Replace fence instructions with Zalasr instructions during acquire or
release operations.

Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
---
 arch/riscv/include/asm/barrier.h | 79 +++++++++++++++++++++++++++-----
 1 file changed, 68 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/include/asm/barrier.h b/arch/riscv/include/asm/barrier.h
index b8c5726d86acb..b1d2a9a85256d 100644
--- a/arch/riscv/include/asm/barrier.h
+++ b/arch/riscv/include/asm/barrier.h
@@ -51,19 +51,76 @@
  */
 #define smp_mb__after_spinlock()	RISCV_FENCE(iorw, iorw)
 
-#define __smp_store_release(p, v)					\
-do {									\
-	compiletime_assert_atomic_type(*p);				\
-	RISCV_FENCE(rw, w);						\
-	WRITE_ONCE(*p, v);						\
+extern void __bad_size_call_parameter(void);
+
+#define __smp_store_release(p, v)						\
+do {										\
+	compiletime_assert_atomic_type(*p);					\
+	switch (sizeof(*p)) {							\
+	case 1:									\
+		asm volatile(ALTERNATIVE("fence rw, w;\t\nsb %0, 0(%1)\t\n",	\
+					 SB_RL(%0, %1) "\t\nnop\t\n",		\
+					 0, RISCV_ISA_EXT_ZALASR, 1)		\
+					 : : "r" (v), "r" (p) : "memory");	\
+		break;								\
+	case 2:									\
+		asm volatile(ALTERNATIVE("fence rw, w;\t\nsh %0, 0(%1)\t\n",	\
+					 SH_RL(%0, %1) "\t\nnop\t\n",		\
+					 0, RISCV_ISA_EXT_ZALASR, 1)		\
+					 : : "r" (v), "r" (p) : "memory");	\
+		break;								\
+	case 4:									\
+		asm volatile(ALTERNATIVE("fence rw, w;\t\nsw %0, 0(%1)\t\n",	\
+					 SW_RL(%0, %1) "\t\nnop\t\n",		\
+					 0, RISCV_ISA_EXT_ZALASR, 1)		\
+					 : : "r" (v), "r" (p) : "memory");	\
+		break;								\
+	case 8:									\
+		asm volatile(ALTERNATIVE("fence rw, w;\t\nsd %0, 0(%1)\t\n",	\
+					 SD_RL(%0, %1) "\t\nnop\t\n",		\
+					 0, RISCV_ISA_EXT_ZALASR, 1)		\
+					 : : "r" (v), "r" (p) : "memory");	\
+		break;								\
+	default:								\
+		__bad_size_call_parameter();					\
+		break;								\
+	}									\
 } while (0)
 
-#define __smp_load_acquire(p)						\
-({									\
-	typeof(*p) ___p1 = READ_ONCE(*p);				\
-	compiletime_assert_atomic_type(*p);				\
-	RISCV_FENCE(r, rw);						\
-	___p1;								\
+#define __smp_load_acquire(p)							\
+({										\
+	TYPEOF_UNQUAL(*p) val;							\
+	compiletime_assert_atomic_type(*p);					\
+	switch (sizeof(*p)) {							\
+	case 1:									\
+		asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n",	\
+					 LB_AQ(%0, %1) "\t\nnop\t\n",		\
+					 0, RISCV_ISA_EXT_ZALASR, 1)		\
+					 : "=r" (val) : "r" (p) : "memory");	\
+		break;								\
+	case 2:									\
+		asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n",	\
+					 LH_AQ(%0, %1) "\t\nnop\t\n",		\
+					 0, RISCV_ISA_EXT_ZALASR, 1)		\
+					 : "=r" (val) : "r" (p) : "memory");	\
+		break;								\
+	case 4:									\
+		asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n",	\
+					 LW_AQ(%0, %1) "\t\nnop\t\n",		\
+					 0, RISCV_ISA_EXT_ZALASR, 1)		\
+					 : "=r" (val) : "r" (p) : "memory");	\
+		break;								\
+	case 8:									\
+		asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n",	\
+					 LD_AQ(%0, %1) "\t\nnop\t\n",		\
+					 0, RISCV_ISA_EXT_ZALASR, 1)		\
+					 : "=r" (val) : "r" (p) : "memory");	\
+		break;								\
+	default:								\
+		__bad_size_call_parameter();					\
+		break;								\
+	}									\
+	val;									\
 })
 
 #ifdef CONFIG_RISCV_ISA_ZAWRS
-- 
2.20.1


^ permalink raw reply related	[flat|nested] 9+ messages in thread

* Re: [PATCH v2 4/4] riscv: Use Zalasr for smp_load_acquire/smp_store_release
  2025-09-02  4:24 ` [PATCH v2 4/4] riscv: Use Zalasr for smp_load_acquire/smp_store_release Xu Lu
@ 2025-09-03  1:06   ` kernel test robot
  0 siblings, 0 replies; 9+ messages in thread
From: kernel test robot @ 2025-09-03  1:06 UTC (permalink / raw)
  To: Xu Lu, robh, krzk+dt, conor+dt, paul.walmsley, palmer, aou, alex,
	ajones, brs
  Cc: oe-kbuild-all, devicetree, linux-riscv, linux-kernel, apw, joe,
	Xu Lu

Hi Xu,

kernel test robot noticed the following build errors:

[auto build test ERROR on robh/for-next]
[also build test ERROR on linus/master v6.17-rc4 next-20250902]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Xu-Lu/riscv-add-ISA-extension-parsing-for-Zalasr/20250902-123357
base:   https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git for-next
patch link:    https://lore.kernel.org/r/20250902042432.78960-5-luxu.kernel%40bytedance.com
patch subject: [PATCH v2 4/4] riscv: Use Zalasr for smp_load_acquire/smp_store_release
config: riscv-randconfig-002-20250903 (https://download.01.org/0day-ci/archive/20250903/202509030832.0uHQ24ec-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 9.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250903/202509030832.0uHQ24ec-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509030832.0uHQ24ec-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from include/asm-generic/bitops/generic-non-atomic.h:7,
                    from include/linux/bitops.h:28,
                    from include/linux/thread_info.h:27,
                    from include/asm-generic/preempt.h:5,
                    from ./arch/riscv/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:79,
                    from include/linux/spinlock.h:56,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:7,
                    from include/linux/mm.h:7,
                    from arch/riscv/kernel/asm-offsets.c:8:
   include/linux/list.h: In function 'list_empty_careful':
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/list.h:409:27: note: in expansion of macro 'smp_load_acquire'
     409 |  struct list_head *next = smp_load_acquire(&head->next);
         |                           ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/list.h:409:27: note: in expansion of macro 'smp_load_acquire'
     409 |  struct list_head *next = smp_load_acquire(&head->next);
         |                           ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/list.h:409:27: note: in expansion of macro 'smp_load_acquire'
     409 |  struct list_head *next = smp_load_acquire(&head->next);
         |                           ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/list.h:409:27: note: in expansion of macro 'smp_load_acquire'
     409 |  struct list_head *next = smp_load_acquire(&head->next);
         |                           ^~~~~~~~~~~~~~~~
   In file included from include/asm-generic/bitops/generic-non-atomic.h:7,
                    from include/linux/bitops.h:28,
                    from include/linux/thread_info.h:27,
                    from include/asm-generic/preempt.h:5,
                    from ./arch/riscv/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:79,
                    from include/linux/spinlock.h:56,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:7,
                    from include/linux/mm.h:7,
                    from arch/riscv/kernel/asm-offsets.c:8:
   include/linux/atomic/atomic-arch-fallback.h: In function 'raw_atomic_read_acquire':
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/atomic/atomic-arch-fallback.h:479:9: note: in expansion of macro 'smp_load_acquire'
     479 |   ret = smp_load_acquire(&(v)->counter);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/atomic/atomic-arch-fallback.h:479:9: note: in expansion of macro 'smp_load_acquire'
     479 |   ret = smp_load_acquire(&(v)->counter);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/atomic/atomic-arch-fallback.h:479:9: note: in expansion of macro 'smp_load_acquire'
     479 |   ret = smp_load_acquire(&(v)->counter);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/atomic/atomic-arch-fallback.h:479:9: note: in expansion of macro 'smp_load_acquire'
     479 |   ret = smp_load_acquire(&(v)->counter);
         |         ^~~~~~~~~~~~~~~~
   include/linux/atomic/atomic-arch-fallback.h: In function 'raw_atomic64_read_acquire':
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/atomic/atomic-arch-fallback.h:2605:9: note: in expansion of macro 'smp_load_acquire'
    2605 |   ret = smp_load_acquire(&(v)->counter);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/atomic/atomic-arch-fallback.h:2605:9: note: in expansion of macro 'smp_load_acquire'
    2605 |   ret = smp_load_acquire(&(v)->counter);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/atomic/atomic-arch-fallback.h:2605:9: note: in expansion of macro 'smp_load_acquire'
    2605 |   ret = smp_load_acquire(&(v)->counter);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/atomic/atomic-arch-fallback.h:2605:9: note: in expansion of macro 'smp_load_acquire'
    2605 |   ret = smp_load_acquire(&(v)->counter);
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h: In function '__seqprop_sequence':
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:211:9: note: in expansion of macro 'smp_load_acquire'
     211 |  return smp_load_acquire(&s->sequence);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:211:9: note: in expansion of macro 'smp_load_acquire'
     211 |  return smp_load_acquire(&s->sequence);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:211:9: note: in expansion of macro 'smp_load_acquire'
     211 |  return smp_load_acquire(&s->sequence);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:211:9: note: in expansion of macro 'smp_load_acquire'
     211 |  return smp_load_acquire(&s->sequence);
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h: In function '__seqprop_raw_spinlock_sequence':
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:226:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     226 | SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t,  false,    raw_spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:226:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     226 | SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t,  false,    raw_spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:226:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     226 | SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t,  false,    raw_spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:226:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     226 | SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t,  false,    raw_spin)
         | ^~~~~~~~~~~~~~~~~
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:226:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     226 | SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t,  false,    raw_spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:226:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     226 | SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t,  false,    raw_spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:226:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     226 | SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t,  false,    raw_spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:226:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     226 | SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t,  false,    raw_spin)
         | ^~~~~~~~~~~~~~~~~
   include/linux/seqlock.h: In function '__seqprop_spinlock_sequence':
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:227:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     227 | SEQCOUNT_LOCKNAME(spinlock,     spinlock_t,      __SEQ_RT, spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:227:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     227 | SEQCOUNT_LOCKNAME(spinlock,     spinlock_t,      __SEQ_RT, spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:227:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     227 | SEQCOUNT_LOCKNAME(spinlock,     spinlock_t,      __SEQ_RT, spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:227:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     227 | SEQCOUNT_LOCKNAME(spinlock,     spinlock_t,      __SEQ_RT, spin)
         | ^~~~~~~~~~~~~~~~~
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:227:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     227 | SEQCOUNT_LOCKNAME(spinlock,     spinlock_t,      __SEQ_RT, spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:227:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     227 | SEQCOUNT_LOCKNAME(spinlock,     spinlock_t,      __SEQ_RT, spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:227:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     227 | SEQCOUNT_LOCKNAME(spinlock,     spinlock_t,      __SEQ_RT, spin)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:227:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     227 | SEQCOUNT_LOCKNAME(spinlock,     spinlock_t,      __SEQ_RT, spin)
         | ^~~~~~~~~~~~~~~~~
   include/linux/seqlock.h: In function '__seqprop_rwlock_sequence':
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:228:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     228 | SEQCOUNT_LOCKNAME(rwlock,       rwlock_t,        __SEQ_RT, read)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:228:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     228 | SEQCOUNT_LOCKNAME(rwlock,       rwlock_t,        __SEQ_RT, read)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:228:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     228 | SEQCOUNT_LOCKNAME(rwlock,       rwlock_t,        __SEQ_RT, read)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:228:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     228 | SEQCOUNT_LOCKNAME(rwlock,       rwlock_t,        __SEQ_RT, read)
         | ^~~~~~~~~~~~~~~~~
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:228:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     228 | SEQCOUNT_LOCKNAME(rwlock,       rwlock_t,        __SEQ_RT, read)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:228:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     228 | SEQCOUNT_LOCKNAME(rwlock,       rwlock_t,        __SEQ_RT, read)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:228:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     228 | SEQCOUNT_LOCKNAME(rwlock,       rwlock_t,        __SEQ_RT, read)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:228:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     228 | SEQCOUNT_LOCKNAME(rwlock,       rwlock_t,        __SEQ_RT, read)
         | ^~~~~~~~~~~~~~~~~
   include/linux/seqlock.h: In function '__seqprop_mutex_sequence':
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:229:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     229 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     mutex)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:229:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     229 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     mutex)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:229:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     229 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     mutex)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:160:17: note: in expansion of macro 'smp_load_acquire'
     160 |  unsigned seq = smp_load_acquire(&s->seqcount.sequence);  \
         |                 ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:229:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     229 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     mutex)
         | ^~~~~~~~~~~~~~~~~
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:229:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     229 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     mutex)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:229:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     229 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     mutex)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:229:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     229 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     mutex)
         | ^~~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:173:9: note: in expansion of macro 'smp_load_acquire'
     173 |   seq = smp_load_acquire(&s->seqcount.sequence);  \
         |         ^~~~~~~~~~~~~~~~
   include/linux/seqlock.h:229:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     229 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     mutex)
         | ^~~~~~~~~~~~~~~~~
   In file included from include/asm-generic/bitops/generic-non-atomic.h:7,
                    from include/linux/bitops.h:28,
                    from include/linux/thread_info.h:27,
                    from include/asm-generic/preempt.h:5,
                    from ./arch/riscv/include/generated/asm/preempt.h:1,
                    from include/linux/preempt.h:79,
                    from include/linux/spinlock.h:56,
                    from include/linux/mmzone.h:8,
                    from include/linux/gfp.h:7,
                    from include/linux/mm.h:7,
                    from arch/riscv/kernel/asm-offsets.c:8:
   include/linux/key.h: In function 'key_read_state':
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/key.h:459:9: note: in expansion of macro 'smp_load_acquire'
     459 |  return smp_load_acquire(&key->state);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/key.h:459:9: note: in expansion of macro 'smp_load_acquire'
     459 |  return smp_load_acquire(&key->state);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/key.h:459:9: note: in expansion of macro 'smp_load_acquire'
     459 |  return smp_load_acquire(&key->state);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/key.h:459:9: note: in expansion of macro 'smp_load_acquire'
     459 |  return smp_load_acquire(&key->state);
         |         ^~~~~~~~~~~~~~~~
   include/linux/fs.h: In function 'i_size_read':
>> arch/riscv/include/asm/barrier.h:96:3: error: read-only variable 'val' used as 'asm' output
      96 |   asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/fs.h:988:9: note: in expansion of macro 'smp_load_acquire'
     988 |  return smp_load_acquire(&inode->i_size);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:102:3: error: read-only variable 'val' used as 'asm' output
     102 |   asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/fs.h:988:9: note: in expansion of macro 'smp_load_acquire'
     988 |  return smp_load_acquire(&inode->i_size);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:108:3: error: read-only variable 'val' used as 'asm' output
     108 |   asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/fs.h:988:9: note: in expansion of macro 'smp_load_acquire'
     988 |  return smp_load_acquire(&inode->i_size);
         |         ^~~~~~~~~~~~~~~~
   arch/riscv/include/asm/barrier.h:114:3: error: read-only variable 'val' used as 'asm' output
     114 |   asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n", \
         |   ^~~
   include/asm-generic/barrier.h:176:29: note: in expansion of macro '__smp_load_acquire'
     176 | #define smp_load_acquire(p) __smp_load_acquire(p)
         |                             ^~~~~~~~~~~~~~~~~~
   include/linux/fs.h:988:9: note: in expansion of macro 'smp_load_acquire'
     988 |  return smp_load_acquire(&inode->i_size);
         |         ^~~~~~~~~~~~~~~~
   make[3]: *** [scripts/Makefile.build:182: arch/riscv/kernel/asm-offsets.s] Error 1 shuffle=1073380763
   make[3]: Target 'prepare' not remade because of errors.
   make[2]: *** [Makefile:1282: prepare0] Error 2 shuffle=1073380763
   make[2]: Target 'prepare' not remade because of errors.
   make[1]: *** [Makefile:248: __sub-make] Error 2 shuffle=1073380763
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [Makefile:248: __sub-make] Error 2 shuffle=1073380763
   make: Target 'prepare' not remade because of errors.


vim +96 arch/riscv/include/asm/barrier.h

    89	
    90	#define __smp_load_acquire(p)							\
    91	({										\
    92		TYPEOF_UNQUAL(*p) val;							\
    93		compiletime_assert_atomic_type(*p);					\
    94		switch (sizeof(*p)) {							\
    95		case 1:									\
  > 96			asm volatile(ALTERNATIVE("lb %0, 0(%1)\t\nfence r, rw\t\n",	\
    97						 LB_AQ(%0, %1) "\t\nnop\t\n",		\
    98						 0, RISCV_ISA_EXT_ZALASR, 1)		\
    99						 : "=r" (val) : "r" (p) : "memory");	\
   100			break;								\
   101		case 2:									\
   102			asm volatile(ALTERNATIVE("lh %0, 0(%1)\t\nfence r, rw\t\n",	\
   103						 LH_AQ(%0, %1) "\t\nnop\t\n",		\
   104						 0, RISCV_ISA_EXT_ZALASR, 1)		\
   105						 : "=r" (val) : "r" (p) : "memory");	\
   106			break;								\
   107		case 4:									\
   108			asm volatile(ALTERNATIVE("lw %0, 0(%1)\t\nfence r, rw\t\n",	\
   109						 LW_AQ(%0, %1) "\t\nnop\t\n",		\
   110						 0, RISCV_ISA_EXT_ZALASR, 1)		\
   111						 : "=r" (val) : "r" (p) : "memory");	\
   112			break;								\
   113		case 8:									\
   114			asm volatile(ALTERNATIVE("ld %0, 0(%1)\t\nfence r, rw\t\n",	\
   115						 LD_AQ(%0, %1) "\t\nnop\t\n",		\
   116						 0, RISCV_ISA_EXT_ZALASR, 1)		\
   117						 : "=r" (val) : "r" (p) : "memory");	\
   118			break;								\
   119		default:								\
   120			__bad_size_call_parameter();					\
   121			break;								\
   122		}									\
   123		val;									\
   124	})
   125	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v2 0/4] riscv: Add Zalasr ISA extension support
  2025-09-02  4:24 [PATCH v2 0/4] riscv: Add Zalasr ISA extension support Xu Lu
                   ` (3 preceding siblings ...)
  2025-09-02  4:24 ` [PATCH v2 4/4] riscv: Use Zalasr for smp_load_acquire/smp_store_release Xu Lu
@ 2025-09-02 16:59 ` Andrea Parri
  2025-09-03 11:41   ` [External] " Xu Lu
  4 siblings, 1 reply; 9+ messages in thread
From: Andrea Parri @ 2025-09-02 16:59 UTC (permalink / raw)
  To: Xu Lu
  Cc: robh, krzk+dt, conor+dt, paul.walmsley, palmer, aou, alex, ajones,
	brs, devicetree, linux-riscv, linux-kernel, apw, joe

> Xu Lu (4):
>   riscv: add ISA extension parsing for Zalasr
>   dt-bindings: riscv: Add Zalasr ISA extension description
>   riscv: Instroduce Zalasr instructions
>   riscv: Use Zalasr for smp_load_acquire/smp_store_release

Informally put, our (Linux) memory consistency model specifies that any
sequence

  spin_unlock(s);
  spin_lock(t);

behaves "as it provides at least FENCE.TSO ordering between operations
which precede the UNLOCK+LOCK sequence and operations which follow the
sequence".  Unless I missing something, the patch set in question breaks
such ordering property (on RISC-V): for example, a "release" annotation,
.RL (as in spin_unlock() -> smp_store_release(), after patch #4) paired
with an "acquire" fence, FENCE R,RW (as could be found in spin_lock() ->
atomic_try_cmpxchg_acquire()) do not provide the specified property.

I _think some solutions to the issue above include:

 a) make sure an .RL annotation is always paired with an .AQ annotation
    and viceversa an .AQ annotation is paired with an .RL annotation
    (this approach matches the current arm64 approach/implementation);

 b) on the opposite direction, always pair FENCE R,RW (or occasionally
    FENCE R,R) with FENCE RW,W (this matches the current approach/the
    current implementation within riscv);

 c) mix the previous two solutions (resp., annotations and fences), but
    make sure to "upgrade" any releases to provide (insert) a FENCE.TSO.

(a) would align RISC-V and ARM64 (which is a good thing IMO), though it
is probably the most invasive approach among the three approaches above
(requiring certain changes to arch/riscv/include/asm/{cmpxchg,atomic}.h,
which are already relatively messy due to the various ZABHA plus ZACAS
switches).  Overall, I'm not too exited at the idea of reviewing any of
those changes, but if the community opts for it, I'll almost definitely
take a closer look with due calm.  ;-)

  Andrea

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [External] Re: [PATCH v2 0/4] riscv: Add Zalasr ISA extension support
  2025-09-02 16:59 ` [PATCH v2 0/4] riscv: Add Zalasr ISA extension support Andrea Parri
@ 2025-09-03 11:41   ` Xu Lu
  0 siblings, 0 replies; 9+ messages in thread
From: Xu Lu @ 2025-09-03 11:41 UTC (permalink / raw)
  To: Andrea Parri
  Cc: robh, krzk+dt, conor+dt, paul.walmsley, palmer, aou, alex, ajones,
	brs, devicetree, linux-riscv, linux-kernel, apw, joe

Hi Andrea,

Great catch! Thanks a lot for your review.

The problem comes from the mixed use of acquire/release semantics via
fence and via real ld.aq/sd.rl. I would prefer your method (a). The
existing atomic acquire/release functions' implementation can be
further modified to amocas.sq/amocas.rl/lr.aq/sc.rl. I will send the
next version after I finish it and hope you can help with review then.

Best regards,
Xu Lu

On Wed, Sep 3, 2025 at 12:59 AM Andrea Parri <parri.andrea@gmail.com> wrote:
>
> > Xu Lu (4):
> >   riscv: add ISA extension parsing for Zalasr
> >   dt-bindings: riscv: Add Zalasr ISA extension description
> >   riscv: Instroduce Zalasr instructions
> >   riscv: Use Zalasr for smp_load_acquire/smp_store_release
>
> Informally put, our (Linux) memory consistency model specifies that any
> sequence
>
>   spin_unlock(s);
>   spin_lock(t);
>
> behaves "as it provides at least FENCE.TSO ordering between operations
> which precede the UNLOCK+LOCK sequence and operations which follow the
> sequence".  Unless I missing something, the patch set in question breaks
> such ordering property (on RISC-V): for example, a "release" annotation,
> .RL (as in spin_unlock() -> smp_store_release(), after patch #4) paired
> with an "acquire" fence, FENCE R,RW (as could be found in spin_lock() ->
> atomic_try_cmpxchg_acquire()) do not provide the specified property.
>
> I _think some solutions to the issue above include:
>
>  a) make sure an .RL annotation is always paired with an .AQ annotation
>     and viceversa an .AQ annotation is paired with an .RL annotation
>     (this approach matches the current arm64 approach/implementation);
>
>  b) on the opposite direction, always pair FENCE R,RW (or occasionally
>     FENCE R,R) with FENCE RW,W (this matches the current approach/the
>     current implementation within riscv);
>
>  c) mix the previous two solutions (resp., annotations and fences), but
>     make sure to "upgrade" any releases to provide (insert) a FENCE.TSO.
>
> (a) would align RISC-V and ARM64 (which is a good thing IMO), though it
> is probably the most invasive approach among the three approaches above
> (requiring certain changes to arch/riscv/include/asm/{cmpxchg,atomic}.h,
> which are already relatively messy due to the various ZABHA plus ZACAS
> switches).  Overall, I'm not too exited at the idea of reviewing any of
> those changes, but if the community opts for it, I'll almost definitely
> take a closer look with due calm.  ;-)
>
>   Andrea

^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2025-09-03 11:42 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-09-02  4:24 [PATCH v2 0/4] riscv: Add Zalasr ISA extension support Xu Lu
2025-09-02  4:24 ` [PATCH v2 1/4] riscv: add ISA extension parsing for Zalasr Xu Lu
2025-09-02  4:24 ` [PATCH v2 2/4] dt-bindings: riscv: Add Zalasr ISA extension description Xu Lu
2025-09-02 19:46   ` Conor Dooley
2025-09-02  4:24 ` [PATCH v2 3/4] riscv: Instroduce Zalasr instructions Xu Lu
2025-09-02  4:24 ` [PATCH v2 4/4] riscv: Use Zalasr for smp_load_acquire/smp_store_release Xu Lu
2025-09-03  1:06   ` kernel test robot
2025-09-02 16:59 ` [PATCH v2 0/4] riscv: Add Zalasr ISA extension support Andrea Parri
2025-09-03 11:41   ` [External] " Xu Lu

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