arm64: capabilities: Add support for checks based on a list of MIDRs

Add helpers for detecting an errata on list of midr ranges
of affected CPUs, with the same work around.

Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/cpufeature.h

@@ -314,6 +314,7 @@ struct arm64_cpu_capabilities {
 			} * const fixed_revs;
 		};
 
+		const struct midr_range *midr_range_list;
 		struct {	/* Feature register checking */
 			u32 sys_reg;
 			u8 field_pos;

arch/arm64/include/asm/cputype.h

@@ -147,6 +147,15 @@ static inline bool is_midr_in_range(u32 midr, struct midr_range const *range)
 				 range->rv_min, range->rv_max);
 }
 
+static inline bool
+is_midr_in_range_list(u32 midr, struct midr_range const *ranges)
+{
+	while (ranges->model)
+		if (is_midr_in_range(midr, ranges++))
+			return true;
+	return false;
+}
+
 /*
  * The CPU ID never changes at run time, so we might as well tell the
  * compiler that it's constant.  Use this function to read the CPU ID

arch/arm64/kernel/cpu_errata.c

@@ -40,6 +40,14 @@ is_affected_midr_range(const struct arm64_cpu_capabilities *entry, int scope)
 	return true;
 }
 
+static bool __maybe_unused
+is_affected_midr_range_list(const struct arm64_cpu_capabilities *entry,
+			    int scope)
+{
+	WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
+	return is_midr_in_range_list(read_cpuid_id(), entry->midr_range_list);
+}
+
 static bool __maybe_unused
 is_kryo_midr(const struct arm64_cpu_capabilities *entry, int scope)
 {
@@ -250,6 +258,10 @@ qcom_enable_link_stack_sanitization(const struct arm64_cpu_capabilities *entry)
 	.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,				\
 	CAP_MIDR_RANGE(model, v_min, r_min, v_max, r_max)
 
+#define CAP_MIDR_RANGE_LIST(list)				\
+	.matches = is_affected_midr_range_list,			\
+	.midr_range_list = list
+
 /* Errata affecting a range of revisions of  given model variant */
 #define ERRATA_MIDR_REV_RANGE(m, var, r_min, r_max)	 \
 	ERRATA_MIDR_RANGE(m, var, r_min, var, r_max)
@@ -263,6 +275,35 @@ qcom_enable_link_stack_sanitization(const struct arm64_cpu_capabilities *entry)
 	.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,			\
 	CAP_MIDR_ALL_VERSIONS(model)
 
+/* Errata affecting a list of midr ranges, with same work around */
+#define ERRATA_MIDR_RANGE_LIST(midr_list)			\
+	.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,			\
+	CAP_MIDR_RANGE_LIST(midr_list)
+
+#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
+
+/*
+ * List of CPUs where we need to issue a psci call to
+ * harden the branch predictor.
+ */
+static const struct midr_range arm64_bp_harden_smccc_cpus[] = {
+	MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
+	MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
+	MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
+	MIDR_ALL_VERSIONS(MIDR_CORTEX_A75),
+	MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
+	MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
+	{},
+};
+
+static const struct midr_range qcom_bp_harden_cpus[] = {
+	MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR_V1),
+	MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR),
+	{},
+};
+
+#endif
+
 const struct arm64_cpu_capabilities arm64_errata[] = {
 #if	defined(CONFIG_ARM64_ERRATUM_826319) || \
 	defined(CONFIG_ARM64_ERRATUM_827319) || \
@@ -406,51 +447,17 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 #ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
 	{
 		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
-		ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
+		ERRATA_MIDR_RANGE_LIST(arm64_bp_harden_smccc_cpus),
 		.cpu_enable = enable_smccc_arch_workaround_1,
 	},
 	{
 		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
-		ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
+		ERRATA_MIDR_RANGE_LIST(qcom_bp_harden_cpus),
-		.cpu_enable = enable_smccc_arch_workaround_1,
-	},
-	{
-		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
-		ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
-		.cpu_enable = enable_smccc_arch_workaround_1,
-	},
-	{
-		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
-		ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A75),
-		.cpu_enable = enable_smccc_arch_workaround_1,
-	},
-	{
-		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
-		ERRATA_MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR_V1),
 		.cpu_enable = qcom_enable_link_stack_sanitization,
 	},
 	{
 		.capability = ARM64_HARDEN_BP_POST_GUEST_EXIT,
-		ERRATA_MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR_V1),
+		ERRATA_MIDR_RANGE_LIST(qcom_bp_harden_cpus),
-	},
-	{
-		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
-		ERRATA_MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR),
-		.cpu_enable = qcom_enable_link_stack_sanitization,
-	},
-	{
-		.capability = ARM64_HARDEN_BP_POST_GUEST_EXIT,
-		ERRATA_MIDR_ALL_VERSIONS(MIDR_QCOM_FALKOR),
-	},
-	{
-		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
-		ERRATA_MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
-		.cpu_enable = enable_smccc_arch_workaround_1,
-	},
-	{
-		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
-		ERRATA_MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
-		.cpu_enable = enable_smccc_arch_workaround_1,
 	},
 #endif
 	{

arch/arm64/kernel/cpufeature.c

@@ -882,6 +882,11 @@ static int __kpti_forced; /* 0: not forced, >0: forced on, <0: forced off */
 static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 				int scope)
 {
+	/* List of CPUs that are not vulnerable and don't need KPTI */
+	static const struct midr_range kpti_safe_list[] = {
+		MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
+		MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
+	};
 	char const *str = "command line option";
 
 	/*
@@ -906,11 +911,8 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 		return true;
 
 	/* Don't force KPTI for CPUs that are not vulnerable */
-	switch (read_cpuid_id() & MIDR_CPU_MODEL_MASK) {
+	if (is_midr_in_range_list(read_cpuid_id(), kpti_safe_list))
-	case MIDR_CAVIUM_THUNDERX2:
-	case MIDR_BRCM_VULCAN:
 		return false;
-	}
 
 	/* Defer to CPU feature registers */
 	return !has_cpuid_feature(entry, scope);