linux-kernel - [PATCH 1/3] arm64: add FEAT_MTE_TAGGED

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Message-Id: <20250403141535.23496-2-yeoreum.yun@arm.com>
Date: Thu,  3 Apr 2025 15:15:33 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: catalin.marinas@....com,
	will@...nel.org,
	broonie@...nel.org,
	anshuman.khandual@....com,
	joey.gouly@....com,
	yury.khrustalev@....com,
	maz@...nel.org,
	oliver.upton@...ux.dev,
	frederic@...nel.org,
	shameerali.kolothum.thodi@...wei.com,
	james.morse@....com,
	mark.rutland@....com,
	huangxiaojia2@...wei.com,
	akpm@...ux-foundation.org,
	surenb@...gle.com,
	robin.murphy@....com
Cc: linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	Yeoreum Yun <yeoreum.yun@....com>
Subject: [PATCH 1/3] arm64: add FEAT_MTE_TAGGED_FAR feature

Add FEAT_MTE_TAGGED_FAR cpucap which makes FAR_ELx report
all non-address bits on a synchronous MTE tag check fault since Armv8.9

Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
---
 arch/arm64/include/asm/hwcap.h      | 1 +
 arch/arm64/include/uapi/asm/hwcap.h | 1 +
 arch/arm64/kernel/cpufeature.c      | 9 +++++++++
 arch/arm64/kernel/cpuinfo.c         | 1 +
 arch/arm64/tools/cpucaps            | 1 +
 5 files changed, 13 insertions(+)

diff --git a/arch/arm64/include/asm/hwcap.h b/arch/arm64/include/asm/hwcap.h
index 1c3f9617d54f..28dd1ac29ecc 100644
--- a/arch/arm64/include/asm/hwcap.h
+++ b/arch/arm64/include/asm/hwcap.h
@@ -176,6 +176,7 @@
 #define KERNEL_HWCAP_POE		__khwcap2_feature(POE)
 
 #define __khwcap3_feature(x)		(const_ilog2(HWCAP3_ ## x) + 128)
+#define KERNEL_HWCAP_MTE_FAR		__khwcap3_feature(MTE_FAR)
 
 /*
  * 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 705a7afa8e58..7d22527a7975 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -143,5 +143,6 @@
 /*
  * HWCAP3 flags - for AT_HWCAP3
  */
+#define HWCAP3_MTE_FAR		(1UL << 0)
 
 #endif /* _UAPI__ASM_HWCAP_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9c4d6d552b25..183b4b7e3074 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -312,6 +312,7 @@ static const struct arm64_ftr_bits ftr_id_aa64pfr1[] = {
 
 static const struct arm64_ftr_bits ftr_id_aa64pfr2[] = {
 	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR2_EL1_FPMR_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_VISIBLE, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR2_EL1_MTEFAR_SHIFT, 4, ID_AA64PFR2_EL1_MTEFAR_NI),
 	ARM64_FTR_END,
 };
 
@@ -2861,6 +2862,13 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.matches = has_cpuid_feature,
 		ARM64_CPUID_FIELDS(ID_AA64PFR1_EL1, MTE, MTE3)
 	},
+	{
+		.desc = "FAR on MTE Tag Check Fault",
+		.capability = ARM64_MTE_FAR,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_cpuid_feature,
+		ARM64_CPUID_FIELDS(ID_AA64PFR2_EL1, MTEFAR, IMP)
+	},
 #endif /* CONFIG_ARM64_MTE */
 	{
 		.desc = "RCpc load-acquire (LDAPR)",
@@ -3191,6 +3199,7 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
 #ifdef CONFIG_ARM64_MTE
 	HWCAP_CAP(ID_AA64PFR1_EL1, MTE, MTE2, CAP_HWCAP, KERNEL_HWCAP_MTE),
 	HWCAP_CAP(ID_AA64PFR1_EL1, MTE, MTE3, CAP_HWCAP, KERNEL_HWCAP_MTE3),
+	HWCAP_CAP(ID_AA64PFR2_EL1, MTEFAR, IMP, CAP_HWCAP, KERNEL_HWCAP_MTE_FAR),
 #endif /* CONFIG_ARM64_MTE */
 	HWCAP_CAP(ID_AA64MMFR0_EL1, ECV, IMP, CAP_HWCAP, KERNEL_HWCAP_ECV),
 	HWCAP_CAP(ID_AA64MMFR1_EL1, AFP, IMP, CAP_HWCAP, KERNEL_HWCAP_AFP),
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 285d7d538342..e2b13454e38a 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -160,6 +160,7 @@ static const char *const hwcap_str[] = {
 	[KERNEL_HWCAP_SME_SFEXPA]	= "smesfexpa",
 	[KERNEL_HWCAP_SME_STMOP]	= "smestmop",
 	[KERNEL_HWCAP_SME_SMOP4]	= "smesmop4",
+	[KERNEL_HWCAP_MTE_FAR]		= "mte_far",
 };
 
 #ifdef CONFIG_COMPAT
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 772c1b008e43..ef62ea04ba37 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -67,6 +67,7 @@ MPAM
 MPAM_HCR
 MTE
 MTE_ASYMM
+MTE_FAR
 SME
 SME_FA64
 SME2
-- 
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}