[PATCH v3 07/25] arm64: enable the Permission Overlay Extension for EL0

[Joey Gouly <joey.gouly@arm.com>]

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@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@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          | 14 ++++++++++++++
 arch/arm64/kernel/cpuinfo.c             |  1 +
 5 files changed, 20 insertions(+)

diff --git a/Documentation/arch/arm64/elf_hwcaps.rst b/Documentation/arch/arm64/elf_hwcaps.rst
index ced7b335e2e0..fe7350a66cea 100644
--- a/Documentation/arch/arm64/elf_hwcaps.rst
+++ b/Documentation/arch/arm64/elf_hwcaps.rst
@@ -317,6 +317,9 @@ HWCAP2_LRCPC3
 HWCAP2_LSE128
     Functionality implied by ID_AA64ISAR0_EL1.Atomic == 0b0011.
 
+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 cd71e09ea14d..9a1aa1e5e25c 100644
--- a/arch/arm64/include/asm/hwcap.h
+++ b/arch/arm64/include/asm/hwcap.h
@@ -142,6 +142,7 @@
 #define KERNEL_HWCAP_SVE_B16B16		__khwcap2_feature(SVE_B16B16)
 #define KERNEL_HWCAP_LRCPC3		__khwcap2_feature(LRCPC3)
 #define KERNEL_HWCAP_LSE128		__khwcap2_feature(LSE128)
+#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 5023599fa278..69f09521b553 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -107,5 +107,6 @@
 #define HWCAP2_SVE_B16B16	(1UL << 45)
 #define HWCAP2_LRCPC3		(1UL << 46)
 #define HWCAP2_LSE128		(1UL << 47)
+#define HWCAP2_POE		(1UL << 48)
 
 #endif /* _UAPI__ASM_HWCAP_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 00b6d516ed3f..02169cb3b84b 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -402,6 +402,8 @@ static const struct arm64_ftr_bits ftr_id_aa64mmfr2[] = {
 };
 
 static const struct arm64_ftr_bits ftr_id_aa64mmfr3[] = {
+	ARM64_FTR_BITS(FTR_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_POE),
+		       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,
@@ -2242,6 +2244,14 @@ static void cpu_enable_mops(const struct arm64_cpu_capabilities *__unused)
 	sysreg_clear_set(sctlr_el1, 0, SCTLR_EL1_MSCEn);
 }
 
+#ifdef CONFIG_ARM64_POE
+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);
+}
+#endif
+
 /* Internal helper functions to match cpu capability type */
 static bool
 cpucap_late_cpu_optional(const struct arm64_cpu_capabilities *cap)
@@ -2737,6 +2747,7 @@ 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)
 	},
 #endif
@@ -2889,6 +2900,9 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
 	HWCAP_CAP(ID_AA64SMFR0_EL1, BI32I32, IMP, CAP_HWCAP, KERNEL_HWCAP_SME_BI32I32),
 	HWCAP_CAP(ID_AA64SMFR0_EL1, F32F32, IMP, CAP_HWCAP, KERNEL_HWCAP_SME_F32F32),
 #endif /* CONFIG_ARM64_SME */
+#ifdef CONFIG_ARM64_POE
+	HWCAP_CAP(ID_AA64MMFR3_EL1, S1POE, IMP, CAP_HWCAP, KERNEL_HWCAP_POE),
+#endif
 	{},
 };
 
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index a257da7b56fe..5515c50f5219 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -130,6 +130,7 @@ static const char *const hwcap_str[] = {
 	[KERNEL_HWCAP_SVE_B16B16]	= "sveb16b16",
 	[KERNEL_HWCAP_LRCPC3]		= "lrcpc3",
 	[KERNEL_HWCAP_LSE128]		= "lse128",
+	[KERNEL_HWCAP_POE]		= "poe",
 };
 
 #ifdef CONFIG_COMPAT
-- 
2.25.1