linux-kernel - [PATCH 07/11] arm64: make the per-task SCTLR2

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Message-Id: <20250804121724.3681531-8-yeoreum.yun@arm.com>
Date: Mon,  4 Aug 2025 13:17:20 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: catalin.marinas@....com,
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Cc: linux-arm-kernel@...ts.infradead.org,
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	Yeoreum Yun <yeoreum.yun@....com>
Subject: [PATCH 07/11] arm64: make the per-task SCTLR2_EL1

Some of field of SCTLR2 registers should be configurable per task
not globally -- i.e) FEAT_CPA2 related field and etc.

For future usage of these fields, make the per-task SCTLR2_EL1.

Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
---
 arch/arm64/include/asm/processor.h | 5 +++++
 arch/arm64/kernel/process.c        | 9 +++++++++
 2 files changed, 14 insertions(+)

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 1bf1a3b16e88..7980161172f7 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -182,6 +182,7 @@ struct thread_struct {
 	u64			mte_ctrl;
 #endif
 	u64			sctlr_user;
+	u64			sctlr2_user;
 	u64			svcr;
 	u64			tpidr2_el0;
 	u64			por_el0;
@@ -256,6 +257,9 @@ static inline void task_set_sve_vl_onexec(struct task_struct *task,
 	(SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | SCTLR_ELx_ENDA | SCTLR_ELx_ENDB |   \
 	 SCTLR_EL1_TCF0_MASK)

+#define SCTLR2_USER_MASK	\
+	(SCTLR2_EL1_EnPACM0 | SCTLR2_EL1_CPTA0 | SCTLR2_EL1_CPTM0)
+
 static inline void arch_thread_struct_whitelist(unsigned long *offset,
 						unsigned long *size)
 {
@@ -368,6 +372,7 @@ struct task_struct;
 unsigned long __get_wchan(struct task_struct *p);

 void update_sctlr_el1(u64 sctlr);
+void update_sctlr2_el1(u64 sctlr2);

 /* Thread switching */
 extern struct task_struct *cpu_switch_to(struct task_struct *prev,
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 08b7042a2e2d..e86325d07fa8 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -699,6 +699,11 @@ void update_sctlr_el1(u64 sctlr)
 	isb();
 }

+void update_sctlr2_el1(u64 sctlr2)
+{
+	sysreg_clear_set(sctlr2_el1, SCTLR2_USER_MASK, sctlr2);
+}
+
 /*
  * Thread switching.
  */
@@ -738,6 +743,10 @@ struct task_struct *__switch_to(struct task_struct *prev,
 	if (prev->thread.sctlr_user != next->thread.sctlr_user)
 		update_sctlr_el1(next->thread.sctlr_user);

+	if (alternative_has_cap_unlikely(ARM64_HAS_SCTLR2) &&
+	    prev->thread.sctlr2_user != next->thread.sctlr2_user)
+		update_sctlr2_el1(next->thread.sctlr2_user);
+
 	/* the actual thread switch */
 	last = cpu_switch_to(prev, next);

--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}