x86/apic: Mark the apic_intr_mode extern for sanity check cleanup

Calling native_smp_prepare_cpus() to prepare for SMP bootup, does some
sanity checking, enables APIC mode and disables SMP feature.

Now, APIC mode setup has been unified to apic_intr_mode_init(), some sanity
checks are redundant and need to be cleanup.

Mark the apic_intr_mode extern to refine the switch and remove the
redundant sanity check.

Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: yinghai@kernel.org
Cc: bhe@redhat.com
Link: https://lkml.kernel.org/r/1505293975-26005-7-git-send-email-douly.fnst@cn.fujitsu.com

arch/x86/include/asm/apic.h

@@ -53,6 +53,15 @@ extern int local_apic_timer_c2_ok;
 extern int disable_apic;
 extern unsigned int lapic_timer_frequency;
 
+extern enum apic_intr_mode_id apic_intr_mode;
+enum apic_intr_mode_id {
+	APIC_PIC,
+	APIC_VIRTUAL_WIRE,
+	APIC_VIRTUAL_WIRE_NO_CONFIG,
+	APIC_SYMMETRIC_IO,
+	APIC_SYMMETRIC_IO_NO_ROUTING
+};
+
 #ifdef CONFIG_SMP
 extern void __inquire_remote_apic(int apicid);
 #else /* CONFIG_SMP */

arch/x86/kernel/apic/apic.c

@@ -1218,13 +1218,7 @@ void __init sync_Arb_IDs(void)
 			APIC_INT_LEVELTRIG | APIC_DM_INIT);
 }
 
-enum apic_intr_mode {
-	APIC_PIC,
-	APIC_VIRTUAL_WIRE,
-	APIC_VIRTUAL_WIRE_NO_CONFIG,
-	APIC_SYMMETRIC_IO,
-	APIC_SYMMETRIC_IO_NO_ROUTING,
-};
+enum apic_intr_mode_id apic_intr_mode;
 
 static int __init apic_intr_mode_select(void)
 {
@@ -1342,7 +1336,9 @@ void __init apic_intr_mode_init(void)
 {
 	bool upmode = false;
 
-	switch (apic_intr_mode_select()) {
+	apic_intr_mode = apic_intr_mode_select();
+
+	switch (apic_intr_mode) {
 	case APIC_PIC:
 		pr_info("APIC: Keep in PIC mode(8259)\n");
 		return;
@@ -1974,8 +1970,8 @@ void __init init_apic_mappings(void)
 		 * yeah -- we lie about apic_version
 		 * in case if apic was disabled via boot option
 		 * but it's not a problem for SMP compiled kernel
-		 * since smp_sanity_check is prepared for such a case
-		 * and disable smp mode
+		 * since apic_intr_mode_select is prepared for such
+		 * a case and disable smp mode
 		 */
 		boot_cpu_apic_version = GET_APIC_VERSION(apic_read(APIC_LVR));
 	}

arch/x86/kernel/smpboot.c

@@ -1190,17 +1190,10 @@ static __init void disable_smp(void)
 	cpumask_set_cpu(0, topology_core_cpumask(0));
 }
 
-enum {
-	SMP_OK,
-	SMP_NO_CONFIG,
-	SMP_NO_APIC,
-	SMP_FORCE_UP,
-};
-
 /*
  * Various sanity checks.
  */
-static int __init smp_sanity_check(unsigned max_cpus)
+static void __init smp_sanity_check(void)
 {
 	preempt_disable();
 
@@ -1237,16 +1230,6 @@ static int __init smp_sanity_check(unsigned max_cpus)
 		physid_set(hard_smp_processor_id(), phys_cpu_present_map);
 	}
 
-	/*
-	 * If we couldn't find an SMP configuration at boot time,
-	 * get out of here now!
-	 */
-	if (!smp_found_config && !acpi_lapic) {
-		preempt_enable();
-		pr_notice("SMP motherboard not detected\n");
-		return SMP_NO_CONFIG;
-	}
-
 	/*
 	 * Should not be necessary because the MP table should list the boot
 	 * CPU too, but we do it for the sake of robustness anyway.
@@ -1257,29 +1240,6 @@ static int __init smp_sanity_check(unsigned max_cpus)
 		physid_set(hard_smp_processor_id(), phys_cpu_present_map);
 	}
 	preempt_enable();
-
-	/*
-	 * If we couldn't find a local APIC, then get out of here now!
-	 */
-	if (APIC_INTEGRATED(boot_cpu_apic_version) &&
-	    !boot_cpu_has(X86_FEATURE_APIC)) {
-		if (!disable_apic) {
-			pr_err("BIOS bug, local APIC #%d not detected!...\n",
-				boot_cpu_physical_apicid);
-			pr_err("... forcing use of dummy APIC emulation (tell your hw vendor)\n");
-		}
-		return SMP_NO_APIC;
-	}
-
-	/*
-	 * If SMP should be disabled, then really disable it!
-	 */
-	if (!max_cpus) {
-		pr_info("SMP mode deactivated\n");
-		return SMP_FORCE_UP;
-	}
-
-	return SMP_OK;
 }
 
 static void __init smp_cpu_index_default(void)
@@ -1338,19 +1298,20 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
 
 	apic_intr_mode_init();
 
-	switch (smp_sanity_check(max_cpus)) {
-	case SMP_NO_CONFIG:
-		disable_smp();
-		return;
-	case SMP_NO_APIC:
+	smp_sanity_check();
+
+	switch (apic_intr_mode) {
+	case APIC_PIC:
+	case APIC_VIRTUAL_WIRE_NO_CONFIG:
 		disable_smp();
 		return;
-	case SMP_FORCE_UP:
+	case APIC_SYMMETRIC_IO_NO_ROUTING:
 		disable_smp();
 		/* Setup local timer */
 		x86_init.timers.setup_percpu_clockev();
 		return;
-	case SMP_OK:
+	case APIC_VIRTUAL_WIRE:
+	case APIC_SYMMETRIC_IO:
 		break;
 	}