1 files changed, 54 insertions, 4 deletions

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 0ead8bfedf20..b2770d753ba3 100644
--- 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))
@@ -1561,8 +1587,6 @@ kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused)
 
 	if (!cpu)
 		arm64_use_ng_mappings = true;
-
-	return;
 }
 #else
 static void
@@ -1734,7 +1758,7 @@ static void cpu_has_fwb(const struct arm64_cpu_capabilities *__unused)
 	u64 val = read_sysreg_s(SYS_CLIDR_EL1);
 
 	/* Check that CLIDR_EL1.LOU{U,IS} are both 0 */
-	WARN_ON(val & (7 << 27 | 7 << 21));
+	WARN_ON(CLIDR_LOUU(val) || CLIDR_LOUIS(val));
 }
 
 #ifdef CONFIG_ARM64_PAN
@@ -1843,6 +1867,9 @@ static void bti_enable(const struct arm64_cpu_capabilities *__unused)
 #ifdef CONFIG_ARM64_MTE
 static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap)
 {
+	sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_ATA | SCTLR_EL1_ATA0);
+	isb();
+
 	/*
 	 * Clear the tags in the zero page. This needs to be done via the
 	 * linear map which has the Tagged attribute.
@@ -2901,15 +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;
 }