1 files changed, 44 insertions, 4 deletions

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 94b8f7fc3310..9f9e0064c8c1 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -51,6 +51,25 @@ unsigned int compat_elf_hwcap2 __read_mostly;
 DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);
 EXPORT_SYMBOL(cpu_hwcaps);
 
+static int dump_cpu_hwcaps(struct notifier_block *self, unsigned long v, void *p)
+{
+	/* file-wide pr_fmt adds "CPU features: " prefix */
+	pr_emerg("0x%*pb\n", ARM64_NCAPS, &cpu_hwcaps);
+	return 0;
+}
+
+static struct notifier_block cpu_hwcaps_notifier = {
+	.notifier_call = dump_cpu_hwcaps
+};
+
+static int __init register_cpu_hwcaps_dumper(void)
+{
+	atomic_notifier_chain_register(&panic_notifier_list,
+				       &cpu_hwcaps_notifier);
+	return 0;
+}
+__initcall(register_cpu_hwcaps_dumper);
+
 DEFINE_STATIC_KEY_ARRAY_FALSE(cpu_hwcap_keys, ARM64_NCAPS);
 EXPORT_SYMBOL(cpu_hwcap_keys);
 
@@ -639,8 +658,10 @@ void update_cpu_features(int cpu,
 	 * Mismatched CPU features are a recipe for disaster. Don't even
 	 * pretend to support them.
 	 */
-	WARN_TAINT_ONCE(taint, TAINT_CPU_OUT_OF_SPEC,
-			"Unsupported CPU feature variation.\n");
+	if (taint) {
+		pr_warn_once("Unsupported CPU feature variation detected.\n");
+		add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);
+	}
 }
 
 u64 read_sanitised_ftr_reg(u32 id)
@@ -985,8 +1006,16 @@ void update_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
  */
 void __init enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps)
 {
-	for (; caps->matches; caps++)
-		if (caps->enable && cpus_have_cap(caps->capability))
+	for (; caps->matches; caps++) {
+		unsigned int num = caps->capability;
+
+		if (!cpus_have_cap(num))
+			continue;
+
+		/* Ensure cpus_have_const_cap(num) works */
+		static_branch_enable(&cpu_hwcap_keys[num]);
+
+		if (caps->enable) {
 			/*
 			 * Use stop_machine() as it schedules the work allowing
 			 * us to modify PSTATE, instead of on_each_cpu() which
@@ -994,6 +1023,8 @@ void __init enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps)
 			 * we return.
 			 */
 			stop_machine(caps->enable, NULL, cpu_online_mask);
+		}
+	}
 }
 
 /*
@@ -1096,6 +1127,14 @@ static void __init setup_feature_capabilities(void)
 	enable_cpu_capabilities(arm64_features);
 }
 
+DEFINE_STATIC_KEY_FALSE(arm64_const_caps_ready);
+EXPORT_SYMBOL(arm64_const_caps_ready);
+
+static void __init mark_const_caps_ready(void)
+{
+	static_branch_enable(&arm64_const_caps_ready);
+}
+
 /*
  * Check if the current CPU has a given feature capability.
  * Should be called from non-preemptible context.
@@ -1131,6 +1170,7 @@ void __init setup_cpu_features(void)
 	/* Set the CPU feature capabilies */
 	setup_feature_capabilities();
 	enable_errata_workarounds();
+	mark_const_caps_ready();
 	setup_elf_hwcaps(arm64_elf_hwcaps);
 
 	if (system_supports_32bit_el0())