Merge remote-tracking branch 'tip/sched/arm64' into for-next/core

[linux-2.6-microblaze.git] / arch / arm64 / kernel / cpufeature.c

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 23b1e3d..b2770d7 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -67,6 +67,7 @@
 #include <linux/crash_dump.h>
 #include <linux/sort.h>
 #include <linux/stop_machine.h>
+#include <linux/sysfs.h>
 #include <linux/types.h>
 #include <linux/minmax.h>
 #include <linux/mm.h>
@@ -1321,6 +1322,31 @@ const struct cpumask *system_32bit_el0_cpumask(void)
        return cpu_possible_mask;
 }
 
+static int __init parse_32bit_el0_param(char *str)
+{
+       allow_mismatched_32bit_el0 = true;
+       return 0;
+}
+early_param("allow_mismatched_32bit_el0", parse_32bit_el0_param);
+
+static ssize_t aarch32_el0_show(struct device *dev,
+                               struct device_attribute *attr, char *buf)
+{
+       const struct cpumask *mask = system_32bit_el0_cpumask();
+
+       return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(mask));
+}
+static const DEVICE_ATTR_RO(aarch32_el0);
+
+static int __init aarch32_el0_sysfs_init(void)
+{
+       if (!allow_mismatched_32bit_el0)
+               return 0;
+
+       return device_create_file(cpu_subsys.dev_root, &dev_attr_aarch32_el0);
+}
+device_initcall(aarch32_el0_sysfs_init);
+
 static bool has_32bit_el0(const struct arm64_cpu_capabilities *entry, int scope)
 {
        if (!has_cpuid_feature(entry, scope))
@@ -2902,15 +2928,38 @@ void __init setup_cpu_features(void)
 
 static int enable_mismatched_32bit_el0(unsigned int cpu)
 {
+       /*
+        * The first 32-bit-capable CPU we detected and so can no longer
+        * be offlined by userspace. -1 indicates we haven't yet onlined
+        * a 32-bit-capable CPU.
+        */
+       static int lucky_winner = -1;
+
        struct cpuinfo_arm64 *info = &per_cpu(cpu_data, cpu);
        bool cpu_32bit = id_aa64pfr0_32bit_el0(info->reg_id_aa64pfr0);
 
        if (cpu_32bit) {
                cpumask_set_cpu(cpu, cpu_32bit_el0_mask);
                static_branch_enable_cpuslocked(&arm64_mismatched_32bit_el0);
-               setup_elf_hwcaps(compat_elf_hwcaps);
        }
 
+       if (cpumask_test_cpu(0, cpu_32bit_el0_mask) == cpu_32bit)
+               return 0;
+
+       if (lucky_winner >= 0)
+               return 0;
+
+       /*
+        * We've detected a mismatch. We need to keep one of our CPUs with
+        * 32-bit EL0 online so that is_cpu_allowed() doesn't end up rejecting
+        * every CPU in the system for a 32-bit task.
+        */
+       lucky_winner = cpu_32bit ? cpu : cpumask_any_and(cpu_32bit_el0_mask,
+                                                        cpu_active_mask);
+       get_cpu_device(lucky_winner)->offline_disabled = true;
+       setup_elf_hwcaps(compat_elf_hwcaps);
+       pr_info("Asymmetric 32-bit EL0 support detected on CPU %u; CPU hot-unplug disabled on CPU %u\n",
+               cpu, lucky_winner);
        return 0;
 }