Hi Will,

On Sun, Dec 14, 2025 at 11:22:44AM +0000, Yeoreum Yun wrote:

quoted

Refactor futex atomic operations using ll/sc method with
clearing PSTATE.PAN to prepare to apply FEAT_LSUI on them.

Signed-off-by: Yeoreum Yun <redacted>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
 arch/arm64/include/asm/futex.h | 128 +++++++++++++++++++++------------
 1 file changed, 82 insertions(+), 46 deletions(-)

diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
index bc06691d2062..f8cb674bdb3f 100644
--- a/arch/arm64/include/asm/futex.h
+++ b/arch/arm64/include/asm/futex.h

@@ -7,17 +7,21 @@

 #include <linux/futex.h>
 #include <linux/uaccess.h>
+#include <linux/stringify.h>

 #include <asm/errno.h>

 #define FUTEX_MAX_LOOPS	128 /* What's the largest number you can think of? */

-#define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg)		\
-do {									\
+#define LLSC_FUTEX_ATOMIC_OP(op, insn)					\
+static __always_inline int						\
+__llsc_futex_atomic_##op(int oparg, u32 __user *uaddr, int *oval)	\
+{									\
 	unsigned int loops = FUTEX_MAX_LOOPS;				\
+	int ret, oldval, tmp;						\
 									\
 	uaccess_enable_privileged();					\
-	asm volatile(							\
+	asm volatile("// __llsc_futex_atomic_" #op "\n"			\
 "	prfm	pstl1strm, %2\n"					\
 "1:	ldxr	%w1, %2\n"						\
 	insn "\n"							\

@@ -35,45 +39,103 @@ do {									\
 	: "r" (oparg), "Ir" (-EAGAIN)					\
 	: "memory");							\
 	uaccess_disable_privileged();					\
-} while (0)
+									\
+	if (!ret)							\
+		*oval = oldval;						\
+									\
+	return ret;							\
+}
+
+LLSC_FUTEX_ATOMIC_OP(add, "add	%w3, %w1, %w5")
+LLSC_FUTEX_ATOMIC_OP(or,  "orr	%w3, %w1, %w5")
+LLSC_FUTEX_ATOMIC_OP(and, "and	%w3, %w1, %w5")
+LLSC_FUTEX_ATOMIC_OP(eor, "eor	%w3, %w1, %w5")
+LLSC_FUTEX_ATOMIC_OP(set, "mov	%w3, %w5")

Since you're reworking this code, how about we take the opportunity to
use named arguments instead of the numbers?

Okay. Let me try this.


--
Sincerely,
Yeoreum Yun