--- zzzz-none-000/linux-3.10.107/arch/arm/kernel/machine_kexec.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/arch/arm/kernel/machine_kexec.c	2021-02-04 17:41:59.000000000 +0000
@@ -16,6 +16,7 @@
 #include <asm/cacheflush.h>
 #include <asm/fncpy.h>
 #include <asm/mach-types.h>
+#include <asm/smp_plat.h>
 #include <asm/system_misc.h>
 
 extern void relocate_new_kernel(void);
@@ -28,6 +29,7 @@
 
 static atomic_t waiting_for_crash_ipi;
 
+static unsigned long dt_mem;
 /*
  * Provide a dummy crash_notes definition while crash dump arrives to arm.
  * This prevents breakage of crash_notes attribute in kernel/ksysfs.c.
@@ -40,6 +42,15 @@
 	int i, err;
 
 	/*
+	 * Validate that if the current HW supports SMP, then the SW supports
+	 * and implements CPU hotplug for the current HW. If not, we won't be
+	 * able to kexec reliably, so fail the prepare operation.
+	 */
+	if (num_possible_cpus() > 1 && platform_can_secondary_boot() &&
+	    !platform_can_cpu_hotplug())
+		return -EINVAL;
+
+	/*
 	 * No segment at default ATAGs address. try to locate
 	 * a dtb using magic.
 	 */
@@ -55,7 +66,7 @@
 			return err;
 
 		if (be32_to_cpu(header) == OF_DT_HEADER)
-			kexec_boot_atags = current_segment->mem;
+			dt_mem = current_segment->mem;
 	}
 	return 0;
 }
@@ -117,12 +128,12 @@
 		msecs--;
 	}
 	if (atomic_read(&waiting_for_crash_ipi) > 0)
-		printk(KERN_WARNING "Non-crashing CPUs did not react to IPI\n");
+		pr_warn("Non-crashing CPUs did not react to IPI\n");
 
 	crash_save_cpu(regs, smp_processor_id());
 	machine_kexec_mask_interrupts();
 
-	printk(KERN_INFO "Loading crashdump kernel...\n");
+	pr_info("Loading crashdump kernel...\n");
 }
 
 /*
@@ -138,10 +149,13 @@
 	unsigned long reboot_entry_phys;
 	void *reboot_code_buffer;
 
-	if (num_online_cpus() > 1) {
-		pr_err("kexec: error: multiple CPUs still online\n");
-		return;
-	}
+	/*
+	 * This can only happen if machine_shutdown() failed to disable some
+	 * CPU, and that can only happen if the checks in
+	 * machine_kexec_prepare() were not correct. If this fails, we can't
+	 * reliably kexec anyway, so BUG_ON is appropriate.
+	 */
+	BUG_ON(num_online_cpus() > 1);
 
 	page_list = image->head & PAGE_MASK;
 
@@ -151,12 +165,12 @@
 	reboot_code_buffer = page_address(image->control_code_page);
 
 	/* Prepare parameters for reboot_code_buffer*/
+	set_kernel_text_rw();
 	kexec_start_address = image->start;
 	kexec_indirection_page = page_list;
 	kexec_mach_type = machine_arch_type;
-	if (!kexec_boot_atags)
-		kexec_boot_atags = image->start - KEXEC_ARM_ZIMAGE_OFFSET + KEXEC_ARM_ATAGS_OFFSET;
-
+	kexec_boot_atags = dt_mem ?: image->start - KEXEC_ARM_ZIMAGE_OFFSET
+				     + KEXEC_ARM_ATAGS_OFFSET;
 
 	/* copy our kernel relocation code to the control code page */
 	reboot_entry = fncpy(reboot_code_buffer,
@@ -165,7 +179,7 @@
 	reboot_entry_phys = (unsigned long)reboot_entry +
 		(reboot_code_buffer_phys - (unsigned long)reboot_code_buffer);
 
-	printk(KERN_INFO "Bye!\n");
+	pr_info("Bye!\n");
 
 	if (kexec_reinit)
 		kexec_reinit();