[PATCH v1 07/20] arm64: enable the Permission Overlay Extension for EL0

[Joey Gouly]

Expose a HWCAP and ID_AA64MMFR3_EL1_S1POE to userspace, so they can be used to
check if the CPU supports the feature.

Signed-off-by: Joey Gouly <joey.gouly at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
---
 Documentation/arch/arm64/elf_hwcaps.rst | 3 +++
 arch/arm64/include/asm/hwcap.h          | 1 +
 arch/arm64/include/uapi/asm/hwcap.h     | 1 +
 arch/arm64/kernel/cpufeature.c          | 8 ++++++++
 arch/arm64/kernel/cpuinfo.c             | 1 +
 5 files changed, 14 insertions(+)

diff --git a/Documentation/arch/arm64/elf_hwcaps.rst b/Documentation/arch/arm64/elf_hwcaps.rst
index 76ff9d7398fd..85f6e9babc7f 100644
--- a/Documentation/arch/arm64/elf_hwcaps.rst
+++ b/Documentation/arch/arm64/elf_hwcaps.rst
@@ -308,6 +308,9 @@ HWCAP2_MOPS
 HWCAP2_HBC
     Functionality implied by ID_AA64ISAR2_EL1.BC == 0b0001.
 
+HWCAP2_POE
+    Functionality implied by ID_AA64MMFR3_EL1.S1POE == 0b0001.
+
 4. Unused AT_HWCAP bits
 -----------------------
 
diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h
index 521267478d18..196f21b7d11b 100644
--- a/arch/arm64/include/asm/hwcap.h
+++ b/arch/arm64/include/asm/hwcap.h
@@ -139,6 +139,7 @@
 #define KERNEL_HWCAP_SME_F16F16		__khwcap2_feature(SME_F16F16)
 #define KERNEL_HWCAP_MOPS		__khwcap2_feature(MOPS)
 #define KERNEL_HWCAP_HBC		__khwcap2_feature(HBC)
+#define KERNEL_HWCAP_POE		__khwcap2_feature(POE)
 
 /*
  * This yields a mask that user programs can use to figure out what
diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
index 53026f45a509..8809ff35d6e4 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -104,5 +104,6 @@
 #define HWCAP2_SME_F16F16	(1UL << 42)
 #define HWCAP2_MOPS		(1UL << 43)
 #define HWCAP2_HBC		(1UL << 44)
+#define HWCAP2_POE		(1UL << 46)
 
 #endif /* _UAPI__ASM_HWCAP_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 902885f59396..9b9145fdb208 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -400,6 +400,7 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr2[] = {
 };
 
 static const struct arm64_ftr_bits ftr_id_aa64mmfr3[] = {
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR3_EL1_S1POE_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR3_EL1_S1PIE_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64MMFR3_EL1_TCRX_SHIFT, 4, 0),
 	ARM64_FTR_END,
@@ -2220,6 +2221,12 @@ static void cpu_enable_mops(const struct arm64_cpu_capabilities *__unused)
 	sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_MSCEn);
 }
 
+static void cpu_enable_poe(const struct arm64_cpu_capabilities *__unused)
+{
+	sysreg_clear_set(REG_TCR2_EL1, 0, TCR2_EL1x_E0POE);
+	sysreg_clear_set(CPACR_EL1, 0, CPACR_ELx_E0POE);
+}
+
 /* Internal helper functions to match cpu capability type */
 static bool
 cpucap_late_cpu_optional(const struct arm64_cpu_capabilities *cap)
@@ -2724,6 +2731,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.capability = ARM64_HAS_S1POE,
 		.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
 		.matches = has_cpuid_feature,
+		.cpu_enable = cpu_enable_poe,
 		ARM64_CPUID_FIELDS(ID_AA64MMFR3_EL1, S1POE, IMP)
 	},
 	{},
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 98fda8500535..5b44e8ab9ab8 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -127,6 +127,7 @@ static const char *const hwcap_str[] = {
 	[KERNEL_HWCAP_SME_F16F16]	= "smef16f16",
 	[KERNEL_HWCAP_MOPS]		= "mops",
 	[KERNEL_HWCAP_HBC]		= "hbc",
+	[KERNEL_HWCAP_POE]		= "poe",
 };
 
 #ifdef CONFIG_COMPAT
-- 
2.25.1