--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -85,16 +85,104 @@ struct arm64_ftr_reg {
 
 extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
 
-/* scope of capability check */
-enum {
-	SCOPE_SYSTEM,
-	SCOPE_LOCAL_CPU,
-};
+/*
+ * CPU capabilities:
+ *
+ * We use arm64_cpu_capabilities to represent system features, errata work
+ * arounds (both used internally by kernel and tracked in cpu_hwcaps) and
+ * ELF HWCAPs (which are exposed to user).
+ *
+ * To support systems with heterogeneous CPUs, we need to make sure that we
+ * detect the capabilities correctly on the system and take appropriate
+ * measures to ensure there are no incompatibilities.
+ *
+ * This comment tries to explain how we treat the capabilities.
+ * Each capability has the following list of attributes :
+ *
+ * 1) Scope of Detection : The system detects a given capability by
+ *    performing some checks at runtime. This could be, e.g, checking the
+ *    value of a field in CPU ID feature register or checking the cpu
+ *    model. The capability provides a call back ( @matches() ) to
+ *    perform the check. Scope defines how the checks should be performed.
+ *    There are two cases:
+ *
+ *     a) SCOPE_LOCAL_CPU: check all the CPUs and "detect" if at least one
+ *        matches. This implies, we have to run the check on all the
+ *        booting CPUs, until the system decides that state of the
+ *        capability is finalised. (See section 2 below)
+ *		Or
+ *     b) SCOPE_SYSTEM: check all the CPUs and "detect" if all the CPUs
+ *        matches. This implies, we run the check only once, when the
+ *        system decides to finalise the state of the capability. If the
+ *        capability relies on a field in one of the CPU ID feature
+ *        registers, we use the sanitised value of the register from the
+ *        CPU feature infrastructure to make the decision.
+ *
+ *    The process of detection is usually denoted by "update" capability
+ *    state in the code.
+ *
+ * 2) Finalise the state : The kernel should finalise the state of a
+ *    capability at some point during its execution and take necessary
+ *    actions if any. Usually, this is done, after all the boot-time
+ *    enabled CPUs are brought up by the kernel, so that it can make
+ *    better decision based on the available set of CPUs. However, there
+ *    are some special cases, where the action is taken during the early
+ *    boot by the primary boot CPU. (e.g, running the kernel at EL2 with
+ *    Virtualisation Host Extensions). The kernel usually disallows any
+ *    changes to the state of a capability once it finalises the capability
+ *    and takes any action, as it may be impossible to execute the actions
+ *    safely. A CPU brought up after a capability is "finalised" is
+ *    referred to as "Late CPU" w.r.t the capability. e.g, all secondary
+ *    CPUs are treated "late CPUs" for capabilities determined by the boot
+ *    CPU.
+ *
+ * 3) Verification: When a CPU is brought online (e.g, by user or by the
+ *    kernel), the kernel should make sure that it is safe to use the CPU,
+ *    by verifying that the CPU is compliant with the state of the
+ *    capabilities finalised already. This happens via :
+ *
+ *	secondary_start_kernel()-> check_local_cpu_capabilities()
+ *
+ *    As explained in (2) above, capabilities could be finalised at
+ *    different points in the execution. Each CPU is verified against the
+ *    "finalised" capabilities and if there is a conflict, the kernel takes
+ *    an action, based on the severity (e.g, a CPU could be prevented from
+ *    booting or cause a kernel panic). The CPU is allowed to "affect" the
+ *    state of the capability, if it has not been finalised already.
+ *
+ * 4) Action: As mentioned in (2), the kernel can take an action for each
+ *    detected capability, on all CPUs on the system. Appropriate actions
+ *    include, turning on an architectural feature, modifying the control
+ *    registers (e.g, SCTLR, TCR etc.) or patching the kernel via
+ *    alternatives. The kernel patching is batched and performed at later
+ *    point. The actions are always initiated only after the capability
+ *    is finalised. This is usally denoted by "enabling" the capability.
+ *    The actions are initiated as follows :
+ *	a) Action is triggered on all online CPUs, after the capability is
+ *	finalised, invoked within the stop_machine() context from
+ *	enable_cpu_capabilitie().
+ *
+ *	b) Any late CPU, brought up after (1), the action is triggered via:
+ *
+ *	  check_local_cpu_capabilities() -> verify_local_cpu_capabilities()
+ *
+ */
+
+
+/* Decide how the capability is detected. On a local CPU vs System wide */
+#define ARM64_CPUCAP_SCOPE_LOCAL_CPU		((u16)BIT(0))
+#define ARM64_CPUCAP_SCOPE_SYSTEM		((u16)BIT(1))
+#define ARM64_CPUCAP_SCOPE_MASK			\
+	(ARM64_CPUCAP_SCOPE_SYSTEM	|	\
+	 ARM64_CPUCAP_SCOPE_LOCAL_CPU)
+
+#define SCOPE_SYSTEM				ARM64_CPUCAP_SCOPE_SYSTEM
+#define SCOPE_LOCAL_CPU				ARM64_CPUCAP_SCOPE_LOCAL_CPU
 
 struct arm64_cpu_capabilities {
 	const char *desc;
 	u16 capability;
-	int def_scope;			/* default scope */
+	u16 type;
 	bool (*matches)(const struct arm64_cpu_capabilities *caps, int scope);
 	/*
 	 * Take the appropriate actions to enable this capability for this CPU.
@@ -119,6 +207,11 @@ struct arm64_cpu_capabilities {
 	};
 };
 
+static inline int cpucap_default_scope(const struct arm64_cpu_capabilities *cap)
+{
+	return cap->type & ARM64_CPUCAP_SCOPE_MASK;
+}
+
 extern DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);
 extern struct static_key_false cpu_hwcap_keys[ARM64_NCAPS];
 extern struct static_key_false arm64_const_caps_ready;
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -406,14 +406,14 @@ static bool has_ssbd_mitigation(const st
 #endif	/* CONFIG_ARM64_SSBD */
 
 #define MIDR_RANGE(model, min, max) \
-	.def_scope = SCOPE_LOCAL_CPU, \
+	.type = ARM64_CPUCAP_SCOPE_LOCAL_CPU, \
 	.matches = is_affected_midr_range, \
 	.midr_model = model, \
 	.midr_range_min = min, \
 	.midr_range_max = max
 
 #define MIDR_ALL_VERSIONS(model) \
-	.def_scope = SCOPE_LOCAL_CPU, \
+	.type = ARM64_CPUCAP_SCOPE_LOCAL_CPU, \
 	.matches = is_affected_midr_range, \
 	.midr_model = model, \
 	.midr_range_min = 0, \
@@ -517,14 +517,14 @@ const struct arm64_cpu_capabilities arm6
 		.desc = "Mismatched cache line size",
 		.capability = ARM64_MISMATCHED_CACHE_LINE_SIZE,
 		.matches = has_mismatched_cache_type,
-		.def_scope = SCOPE_LOCAL_CPU,
+		.type = ARM64_CPUCAP_SCOPE_LOCAL_CPU,
 		.cpu_enable = cpu_enable_trap_ctr_access,
 	},
 	{
 		.desc = "Mismatched cache type",
 		.capability = ARM64_MISMATCHED_CACHE_TYPE,
 		.matches = has_mismatched_cache_type,
-		.def_scope = SCOPE_LOCAL_CPU,
+		.type = ARM64_CPUCAP_SCOPE_LOCAL_CPU,
 		.cpu_enable = cpu_enable_trap_ctr_access,
 	},
 #ifdef CONFIG_QCOM_FALKOR_ERRATUM_1003
@@ -538,7 +538,7 @@ const struct arm64_cpu_capabilities arm6
 	{
 		.desc = "Qualcomm Technologies Kryo erratum 1003",
 		.capability = ARM64_WORKAROUND_QCOM_FALKOR_E1003,
-		.def_scope = SCOPE_LOCAL_CPU,
+		.type = ARM64_CPUCAP_SCOPE_LOCAL_CPU,
 		.midr_model = MIDR_QCOM_KRYO,
 		.matches = is_kryo_midr,
 	},
@@ -613,7 +613,7 @@ const struct arm64_cpu_capabilities arm6
 #ifdef CONFIG_ARM64_SSBD
 	{
 		.desc = "Speculative Store Bypass Disable",
-		.def_scope = SCOPE_LOCAL_CPU,
+		.type = ARM64_CPUCAP_SCOPE_LOCAL_CPU,
 		.capability = ARM64_SSBD,
 		.matches = has_ssbd_mitigation,
 	},
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -924,7 +924,7 @@ static const struct arm64_cpu_capabiliti
 	{
 		.desc = "GIC system register CPU interface",
 		.capability = ARM64_HAS_SYSREG_GIC_CPUIF,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = has_useable_gicv3_cpuif,
 		.sys_reg = SYS_ID_AA64PFR0_EL1,
 		.field_pos = ID_AA64PFR0_GIC_SHIFT,
@@ -935,7 +935,7 @@ static const struct arm64_cpu_capabiliti
 	{
 		.desc = "Privileged Access Never",
 		.capability = ARM64_HAS_PAN,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = has_cpuid_feature,
 		.sys_reg = SYS_ID_AA64MMFR1_EL1,
 		.field_pos = ID_AA64MMFR1_PAN_SHIFT,
@@ -948,7 +948,7 @@ static const struct arm64_cpu_capabiliti
 	{
 		.desc = "LSE atomic instructions",
 		.capability = ARM64_HAS_LSE_ATOMICS,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = has_cpuid_feature,
 		.sys_reg = SYS_ID_AA64ISAR0_EL1,
 		.field_pos = ID_AA64ISAR0_ATOMICS_SHIFT,
@@ -959,14 +959,14 @@ static const struct arm64_cpu_capabiliti
 	{
 		.desc = "Software prefetching using PRFM",
 		.capability = ARM64_HAS_NO_HW_PREFETCH,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = has_no_hw_prefetch,
 	},
 #ifdef CONFIG_ARM64_UAO
 	{
 		.desc = "User Access Override",
 		.capability = ARM64_HAS_UAO,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = has_cpuid_feature,
 		.sys_reg = SYS_ID_AA64MMFR2_EL1,
 		.field_pos = ID_AA64MMFR2_UAO_SHIFT,
@@ -980,21 +980,21 @@ static const struct arm64_cpu_capabiliti
 #ifdef CONFIG_ARM64_PAN
 	{
 		.capability = ARM64_ALT_PAN_NOT_UAO,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = cpufeature_pan_not_uao,
 	},
 #endif /* CONFIG_ARM64_PAN */
 	{
 		.desc = "Virtualization Host Extensions",
 		.capability = ARM64_HAS_VIRT_HOST_EXTN,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = runs_at_el2,
 		.cpu_enable = cpu_copy_el2regs,
 	},
 	{
 		.desc = "32-bit EL0 Support",
 		.capability = ARM64_HAS_32BIT_EL0,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = has_cpuid_feature,
 		.sys_reg = SYS_ID_AA64PFR0_EL1,
 		.sign = FTR_UNSIGNED,
@@ -1004,14 +1004,14 @@ static const struct arm64_cpu_capabiliti
 	{
 		.desc = "Reduced HYP mapping offset",
 		.capability = ARM64_HYP_OFFSET_LOW,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = hyp_offset_low,
 	},
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 	{
 		.desc = "Kernel page table isolation (KPTI)",
 		.capability = ARM64_UNMAP_KERNEL_AT_EL0,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = unmap_kernel_at_el0,
 		.cpu_enable = kpti_install_ng_mappings,
 	},
@@ -1019,7 +1019,7 @@ static const struct arm64_cpu_capabiliti
 	{
 		/* FP/SIMD is not implemented */
 		.capability = ARM64_HAS_NO_FPSIMD,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.min_field_value = 0,
 		.matches = has_no_fpsimd,
 	},
@@ -1027,7 +1027,7 @@ static const struct arm64_cpu_capabiliti
 	{
 		.desc = "Data cache clean to Point of Persistence",
 		.capability = ARM64_HAS_DCPOP,
-		.def_scope = SCOPE_SYSTEM,
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,
 		.matches = has_cpuid_feature,
 		.sys_reg = SYS_ID_AA64ISAR1_EL1,
 		.field_pos = ID_AA64ISAR1_DPB_SHIFT,
@@ -1037,16 +1037,16 @@ static const struct arm64_cpu_capabiliti
 	{},
 };
 
-#define HWCAP_CAP(reg, field, s, min_value, type, cap)	\
+#define HWCAP_CAP(reg, field, s, min_value, cap_type, cap)	\
 	{							\
 		.desc = #cap,					\
-		.def_scope = SCOPE_SYSTEM,			\
+		.type = ARM64_CPUCAP_SCOPE_SYSTEM,		\
 		.matches = has_cpuid_feature,			\
 		.sys_reg = reg,					\
 		.field_pos = field,				\
 		.sign = s,					\
 		.min_field_value = min_value,			\
-		.hwcap_type = type,				\
+		.hwcap_type = cap_type,				\
 		.hwcap = cap,					\
 	}
 
@@ -1140,7 +1140,7 @@ static void __init setup_elf_hwcaps(cons
 	/* We support emulation of accesses to CPU ID feature registers */
 	elf_hwcap |= HWCAP_CPUID;
 	for (; hwcaps->matches; hwcaps++)
-		if (hwcaps->matches(hwcaps, hwcaps->def_scope))
+		if (hwcaps->matches(hwcaps, cpucap_default_scope(hwcaps)))
 			cap_set_elf_hwcap(hwcaps);
 }
 
@@ -1167,7 +1167,7 @@ static void update_cpu_capabilities(cons
 				    const char *info)
 {
 	for (; caps->matches; caps++) {
-		if (!caps->matches(caps, caps->def_scope))
+		if (!caps->matches(caps, cpucap_default_scope(caps)))
 			continue;
 
 		if (!cpus_have_cap(caps->capability) && caps->desc)
