Subject: [PATCH RFC v8 09/24] arm64: Enable kpkeys

From: Kevin Brodsky <[email-masked]>
Date: Tue, 26 May 2026 12:15:58 +0100

This is the final step to enable kpkeys on arm64. We enable
POE at EL1 by setting TCR2_EL1.POE, and initialise POR_EL1 to the
default value, enabling access to the default pkey/POIndex (0).
An ISB is added so that POE restrictions are enforced immediately.

Having done this, we can now select ARCH_HAS_KPKEYS if ARM64_POE is
enabled.

Signed-off-by: Kevin Brodsky <[email-masked]>
---
 arch/arm64/Kconfig             | 1 +
 arch/arm64/kernel/cpufeature.c | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index fe60738e5943..ab06324a50ae 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2145,6 +2145,7 @@ config ARM64_POE
 	def_bool y
 	select ARCH_USES_HIGH_VMA_FLAGS
 	select ARCH_HAS_PKEYS
+	select ARCH_HAS_KPKEYS
 	help
 	  The Permission Overlay Extension is used to implement Memory
 	  Protection Keys. Memory Protection Keys provides a mechanism for
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 6d53bb15cf7b..e032322c0c36 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -76,6 +76,7 @@
 #include <linux/kasan.h>
 #include <linux/percpu.h>
 #include <linux/sched/isolation.h>
+#include <linux/kpkeys.h>
 
 #include <asm/arm_pmuv3.h>
 #include <asm/cpu.h>
@@ -2451,8 +2452,10 @@ static void cpu_enable_mops(const struct arm64_cpu_capabilities *__unused)
 #ifdef CONFIG_ARM64_POE
 static void cpu_enable_poe(const struct arm64_cpu_capabilities *__unused)
 {
-	sysreg_clear_set(REG_TCR2_EL1, 0, TCR2_EL1_E0POE);
+	write_sysreg_s(POR_EL1_INIT, SYS_POR_EL1);
+	sysreg_clear_set(REG_TCR2_EL1, 0, TCR2_EL1_E0POE | TCR2_EL1_POE);
 	sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_E0POE);
+	isb();
 }
 #endif

-- 
2.51.2