linux-kernel - [PATCH v11 9/9] arm64: armv8_deprecated: apply FEAT

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Message-Id: <20251106094023.1371246-10-yeoreum.yun@arm.com>
Date: Thu,  6 Nov 2025 09:40:23 +0000
From: Yeoreum Yun <yeoreum.yun@....com>
To: catalin.marinas@....com,
	will@...nel.org,
	maz@...nel.org,
	broonie@...nel.org,
	oliver.upton@...ux.dev,
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	mark.rutland@....com
Cc: linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
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	kvm@...r.kernel.org,
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	Yeoreum Yun <yeoreum.yun@....com>
Subject: [PATCH v11 9/9] arm64: armv8_deprecated: apply FEAT_LSUI for swpX emulation.

apply FEAT_LSUI instruction to emulate deprecated swpX instruction.

Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
---
 arch/arm64/kernel/armv8_deprecated.c | 77 +++++++++++++++++++++++++---
 1 file changed, 71 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
index d15e35f1075c..b8e6d71f766d 100644
--- a/arch/arm64/kernel/armv8_deprecated.c
+++ b/arch/arm64/kernel/armv8_deprecated.c
@@ -13,6 +13,7 @@
 #include <linux/uaccess.h>
 
 #include <asm/cpufeature.h>
+#include <asm/lsui.h>
 #include <asm/insn.h>
 #include <asm/sysreg.h>
 #include <asm/system_misc.h>
@@ -86,13 +87,77 @@ static unsigned int __maybe_unused aarch32_check_condition(u32 opcode, u32 psr)
  *	   Rn  = address
  */
 
+/* Arbitrary constant to ensure forward-progress of the loop */
+#define __SWP_LOOPS	4
+
+#ifdef CONFIG_AS_HAS_LSUI
+static __always_inline int
+__lsui_user_swp_asm(unsigned int *data, unsigned int addr)
+{
+	int err = 0;
+	unsigned int temp;
+
+	asm volatile("// __lsui_user_swp_asm\n"
+	__LSUI_PREAMBLE
+	"1:	swpt		%w1, %w2, [%3]\n"
+	"	mov		%w1, %w2\n"
+	"2:\n"
+	_ASM_EXTABLE_UACCESS_ERR(1b, 2b, %w0)
+	: "+r" (err), "+r" (*data), "=&r" (temp)
+	: "r" ((unsigned long)addr)
+	: "memory");
+
+	return err;
+}
+
+static __always_inline int
+__lsui_user_swpb_asm(unsigned int *data, unsigned int addr)
+{
+	u8 i, idx;
+	int err = -EAGAIN;
+	u64 __user *addr_al;
+	u64 oldval;
+	union {
+		u64 var;
+		u8 raw[sizeof(u64)];
+	} newval, curval;
+
+	idx = addr & (sizeof(u64) - 1);
+	addr_al = (u64 __user *)ALIGN_DOWN(addr, sizeof(u64));
+
+	for (i = 0; i < __SWP_LOOPS; i++) {
+		if (get_user(oldval, addr_al))
+			return -EFAULT;
+
+		curval.var = newval.var = oldval;
+		newval.raw[idx] = *data;
+
+		asm volatile("// __lsui_user_swpb_asm\n"
+		__LSUI_PREAMBLE
+		"1: cast	%x2, %x3, %1\n"
+		"2:\n"
+		_ASM_EXTABLE_UACCESS_ERR(1b, 2b, %w0)
+		: "+r" (err), "+Q" (*addr_al), "+r" (curval.var)
+		: "r" (newval.var)
+		: "memory");
+
+		if (curval.var == oldval) {
+			err = 0;
+			break;
+		}
+	}
+
+	if (!err)
+		*data = curval.raw[idx];
+
+	return err;
+}
+#endif /* CONFIG_AS_HAS_LSUI */
+
 /*
  * Error-checking SWP macros implemented using ldxr{b}/stxr{b}
  */
 
-/* Arbitrary constant to ensure forward-progress of the LL/SC loop */
-#define __SWP_LL_SC_LOOPS	4
-
 #define LLSC_USER_SWPX(B)					\
 static __always_inline int					\
 __llsc_user_swp##B##_asm(unsigned int *data, unsigned int addr)	\
@@ -117,7 +182,7 @@ __llsc_user_swp##B##_asm(unsigned int *data, unsigned int addr)	\
 	_ASM_EXTABLE_UACCESS_ERR(1b, 3b, %w0)			\
 	: "=&r" (err), "+r" (*data), "=&r" (temp), "=&r" (temp2)\
 	: "r" ((unsigned long)addr), "i" (-EAGAIN),		\
-	  "i" (__SWP_LL_SC_LOOPS)				\
+	  "i" (__SWP_LOOPS)					\
 	: "memory");						\
 	uaccess_disable_privileged();				\
 								\
@@ -128,9 +193,9 @@ LLSC_USER_SWPX()
 LLSC_USER_SWPX(b)
 
 #define __user_swp_asm(data, addr) \
-	__llsc_user_swp_asm(data, addr)
+	__lsui_llsc_body(user_swp_asm, data, addr)
 #define __user_swpb_asm(data, addr) \
-	__llsc_user_swpb_asm(data, addr)
+	__lsui_llsc_body(user_swpb_asm, data, addr)
 
 /*
  * Bit 22 of the instruction encoding distinguishes between
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}