x86 kdump: extract kdump-specific code from crash_nmi_callback()

Impact: cleanup

The NMI CPU-halting code will be used on non-kdump cases, also
(e.g. emergency_reboot when virtualization is enabled).
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/crash.c

@@ -35,19 +35,34 @@ static int crashing_cpu;
 #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
 static atomic_t waiting_for_crash_ipi;
 
-static int crash_nmi_callback(struct notifier_block *self,
-			unsigned long val, void *data)
+static void kdump_nmi_callback(int cpu, struct die_args *args)
 {
 	struct pt_regs *regs;
 #ifdef CONFIG_X86_32
 	struct pt_regs fixed_regs;
 #endif
+
+	regs = args->regs;
+
+#ifdef CONFIG_X86_32
+	if (!user_mode_vm(regs)) {
+		crash_fixup_ss_esp(&fixed_regs, regs);
+		regs = &fixed_regs;
+	}
+#endif
+	crash_save_cpu(regs, cpu);
+
+	disable_local_APIC();
+}
+
+static int crash_nmi_callback(struct notifier_block *self,
+			unsigned long val, void *data)
+{
 	int cpu;
 
 	if (val != DIE_NMI_IPI)
 		return NOTIFY_OK;
 
-	regs = ((struct die_args *)data)->regs;
 	cpu = raw_smp_processor_id();
 
 	/* Don't do anything if this handler is invoked on crashing cpu.
@@ -58,14 +73,8 @@ static int crash_nmi_callback(struct notifier_block *self,
 		return NOTIFY_STOP;
 	local_irq_disable();
 
-#ifdef CONFIG_X86_32
-	if (!user_mode_vm(regs)) {
-		crash_fixup_ss_esp(&fixed_regs, regs);
-		regs = &fixed_regs;
-	}
-#endif
-	crash_save_cpu(regs, cpu);
-	disable_local_APIC();
+	kdump_nmi_callback(cpu, (struct die_args *)data);
+
 	atomic_dec(&waiting_for_crash_ipi);
 	/* Assume hlt works */
 	halt();