--- zzzz-none-000/linux-4.4.60/arch/arm/mm/highmem.c	2017-04-08 07:53:53.000000000 +0000
+++ scorpion-1750e-727/linux-4.4.60/arch/arm/mm/highmem.c	2021-02-04 17:41:59.000000000 +0000
@@ -10,6 +10,7 @@
  * published by the Free Software Foundation.
  */
 
+#include <linux/cpu.h>
 #include <linux/module.h>
 #include <linux/highmem.h>
 #include <linux/interrupt.h>
@@ -147,3 +148,58 @@
 
 	return (void *)vaddr;
 }
+
+#ifdef CONFIG_ARCH_WANT_KMAP_ATOMIC_FLUSH
+static void kmap_remove_unused_cpu(int cpu)
+{
+	int start_idx, idx, type;
+
+	pagefault_disable();
+	type = kmap_atomic_idx();
+	start_idx = type + 1 + KM_TYPE_NR * cpu;
+
+	for (idx = start_idx; idx < KM_TYPE_NR + KM_TYPE_NR * cpu; idx++) {
+		unsigned long vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+		pte_t ptep;
+
+		ptep = get_top_pte(vaddr);
+		if (ptep)
+			set_top_pte(vaddr, __pte(0));
+	}
+	pagefault_enable();
+}
+
+static void kmap_remove_unused(void *unused)
+{
+	kmap_remove_unused_cpu(smp_processor_id());
+}
+
+void kmap_atomic_flush_unused(void)
+{
+	on_each_cpu(kmap_remove_unused, NULL, 1);
+}
+
+static int hotplug_kmap_atomic_callback(struct notifier_block *nfb,
+					unsigned long action, void *hcpu)
+{
+	switch (action & (~CPU_TASKS_FROZEN)) {
+	case CPU_DYING:
+		kmap_remove_unused_cpu((int)hcpu);
+		break;
+	default:
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block hotplug_kmap_atomic_notifier = {
+	.notifier_call = hotplug_kmap_atomic_callback,
+};
+
+static int __init init_kmap_atomic(void)
+{
+	return register_hotcpu_notifier(&hotplug_kmap_atomic_notifier);
+}
+early_initcall(init_kmap_atomic);
+#endif