linux-kernel - [PATCH 2/4] arm64: cpufeature: add Allocation Tag Access Permission (MTE

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Message-ID: <20241028094014.2596619-3-aneesh.kumar@kernel.org>
Date: Mon, 28 Oct 2024 15:10:12 +0530
From: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev
Cc: Suzuki K Poulose <Suzuki.Poulose@....com>,
	Steven Price <steven.price@....com>,
	Will Deacon <will@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Marc Zyngier <maz@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	"Aneesh Kumar K.V (Arm)" <aneesh.kumar@...nel.org>
Subject: [PATCH 2/4] arm64: cpufeature: add Allocation Tag Access Permission (MTE_PERM) feature

This indicates if the system supports MTE_PERM. This will be used by KVM
for stage 2 mapping. This is a CPUCAP_SYSTEM feature because if we enable
the feature all cpus must have it.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@...nel.org>
---
 arch/arm64/include/asm/cpufeature.h | 5 +++++
 arch/arm64/include/asm/memory.h     | 2 ++
 arch/arm64/kernel/cpufeature.c      | 9 +++++++++
 arch/arm64/tools/cpucaps            | 1 +
 4 files changed, 17 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 3d261cc123c1..6e6631890021 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -805,6 +805,11 @@ static inline bool system_supports_mte(void)
 	return alternative_has_cap_unlikely(ARM64_MTE);
 }
 
+static inline bool system_supports_notagaccess(void)
+{
+	return alternative_has_cap_unlikely(ARM64_MTE_PERM);
+}
+
 static inline bool system_has_prio_mask_debugging(void)
 {
 	return IS_ENABLED(CONFIG_ARM64_DEBUG_PRIORITY_MASKING) &&
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index ca42f6d87c16..006a649d4ac7 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -179,6 +179,7 @@
  * Memory types for Stage-2 translation
  */
 #define MT_S2_NORMAL			0b1111
+#define MT_S2_NORMAL_NOTAGACCESS	0b0100
 #define MT_S2_NORMAL_NC			0b0101
 #define MT_S2_DEVICE_nGnRE		0b0001
 
@@ -187,6 +188,7 @@
  * Stage-2 enforces Normal-WB and Device-nGnRE
  */
 #define MT_S2_FWB_NORMAL		0b0110
+#define MT_S2_FWB_NORMAL_NOTAGACCESS	0b1110
 #define MT_S2_FWB_NORMAL_NC		0b0101
 #define MT_S2_FWB_DEVICE_nGnRE		0b0001
 
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 718728a85430..608e24e313ad 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -305,6 +305,7 @@ 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_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR2_EL1_MTEPERM_SHIFT, 4, 0),
 	ARM64_FTR_END,
 };
 
@@ -2742,6 +2743,14 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.matches = has_cpuid_feature,
 		ARM64_CPUID_FIELDS(ID_AA64PFR1_EL1, MTE, MTE3)
 	},
+	{
+		.desc = "MTE Allocation Tag Access Permission",
+		.capability = ARM64_MTE_PERM,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_cpuid_feature,
+		ARM64_CPUID_FIELDS(ID_AA64PFR2_EL1, MTEPERM, IMP)
+	},
+
 #endif /* CONFIG_ARM64_MTE */
 	{
 		.desc = "RCpc load-acquire (LDAPR)",
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index eedb5acc21ed..81c6599d2a95 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -62,6 +62,7 @@ KVM_PROTECTED_MODE
 MISMATCHED_CACHE_TYPE
 MTE
 MTE_ASYMM
+MTE_PERM
 SME
 SME_FA64
 SME2
-- 
2.43.0