---

yaml
---
r: 339129
b: refs/heads/master
c: e1c467e
h: refs/heads/master
i:
  339127: 7db12a6
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 3e2a0cc3cdc19e0518ae87583add40ea1bf55b67
+refs/heads/master: e1c467e69040c3be68959332959c07fb3d818e87

trunk/arch/x86/include/asm/cpu.h

@@ -28,6 +28,7 @@ struct x86_cpu {
 #ifdef CONFIG_HOTPLUG_CPU
 extern int arch_register_cpu(int num);
 extern void arch_unregister_cpu(int);
+extern void __cpuinit start_cpu0(void);
 #endif
 
 DECLARE_PER_CPU(int, cpu_state);

trunk/arch/x86/kernel/smpboot.c

@@ -138,15 +138,17 @@ static void __cpuinit smp_callin(void)
 	 * we may get here before an INIT-deassert IPI reaches
 	 * our local APIC.  We have to wait for the IPI or we'll
 	 * lock up on an APIC access.
+	 *
+	 * Since CPU0 is not wakened up by INIT, it doesn't wait for the IPI.
 	 */
-	if (apic->wait_for_init_deassert)
+	cpuid = smp_processor_id();
+	if (apic->wait_for_init_deassert && cpuid != 0)
 		apic->wait_for_init_deassert(&init_deasserted);
 
 	/*
 	 * (This works even if the APIC is not enabled.)
 	 */
 	phys_id = read_apic_id();
-	cpuid = smp_processor_id();
 	if (cpumask_test_cpu(cpuid, cpu_callin_mask)) {
 		panic("%s: phys CPU#%d, CPU#%d already present??\n", __func__,
 					phys_id, cpuid);
@@ -228,6 +230,8 @@ static void __cpuinit smp_callin(void)
 	cpumask_set_cpu(cpuid, cpu_callin_mask);
 }
 
+static int cpu0_logical_apicid;
+static int enable_start_cpu0;
 /*
  * Activate a secondary processor.
  */
@@ -243,6 +247,8 @@ notrace static void __cpuinit start_secondary(void *unused)
 	preempt_disable();
 	smp_callin();
 
+	enable_start_cpu0 = 0;
+
 #ifdef CONFIG_X86_32
 	/* switch away from the initial page table */
 	load_cr3(swapper_pg_dir);
@@ -492,15 +498,15 @@ void __inquire_remote_apic(int apicid)
  * won't ... remember to clear down the APIC, etc later.
  */
 int __cpuinit
-wakeup_secondary_cpu_via_nmi(int logical_apicid, unsigned long start_eip)
+wakeup_secondary_cpu_via_nmi(int apicid, unsigned long start_eip)
 {
 	unsigned long send_status, accept_status = 0;
 	int maxlvt;
 
 	/* Target chip */
 	/* Boot on the stack */
 	/* Kick the second */
-	apic_icr_write(APIC_DM_NMI | apic->dest_logical, logical_apicid);
+	apic_icr_write(APIC_DM_NMI | apic->dest_logical, apicid);
 
 	pr_debug("Waiting for send to finish...\n");
 	send_status = safe_apic_wait_icr_idle();
@@ -660,6 +666,63 @@ static void __cpuinit announce_cpu(int cpu, int apicid)
 			node, cpu, apicid);
 }
 
+static int wakeup_cpu0_nmi(unsigned int cmd, struct pt_regs *regs)
+{
+	int cpu;
+
+	cpu = smp_processor_id();
+	if (cpu == 0 && !cpu_online(cpu) && enable_start_cpu0)
+		return NMI_HANDLED;
+
+	return NMI_DONE;
+}
+
+/*
+ * Wake up AP by INIT, INIT, STARTUP sequence.
+ *
+ * Instead of waiting for STARTUP after INITs, BSP will execute the BIOS
+ * boot-strap code which is not a desired behavior for waking up BSP. To
+ * void the boot-strap code, wake up CPU0 by NMI instead.
+ *
+ * This works to wake up soft offlined CPU0 only. If CPU0 is hard offlined
+ * (i.e. physically hot removed and then hot added), NMI won't wake it up.
+ * We'll change this code in the future to wake up hard offlined CPU0 if
+ * real platform and request are available.
+ */
+static int __cpuinit
+wakeup_cpu_via_init_nmi(int cpu, unsigned long start_ip, int apicid,
+	       int *cpu0_nmi_registered)
+{
+	int id;
+	int boot_error;
+
+	/*
+	 * Wake up AP by INIT, INIT, STARTUP sequence.
+	 */
+	if (cpu)
+		return wakeup_secondary_cpu_via_init(apicid, start_ip);
+
+	/*
+	 * Wake up BSP by nmi.
+	 *
+	 * Register a NMI handler to help wake up CPU0.
+	 */
+	boot_error = register_nmi_handler(NMI_LOCAL,
+					  wakeup_cpu0_nmi, 0, "wake_cpu0");
+
+	if (!boot_error) {
+		enable_start_cpu0 = 1;
+		*cpu0_nmi_registered = 1;
+		if (apic->dest_logical == APIC_DEST_LOGICAL)
+			id = cpu0_logical_apicid;
+		else
+			id = apicid;
+		boot_error = wakeup_secondary_cpu_via_nmi(id, start_ip);
+	}
+
+	return boot_error;
+}
+
 /*
  * NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad
  * (ie clustered apic addressing mode), this is a LOGICAL apic ID.
@@ -675,6 +738,7 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
 
 	unsigned long boot_error = 0;
 	int timeout;
+	int cpu0_nmi_registered = 0;
 
 	/* Just in case we booted with a single CPU. */
 	alternatives_enable_smp();
@@ -722,13 +786,16 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
 	}
 
 	/*
-	 * Kick the secondary CPU. Use the method in the APIC driver
-	 * if it's defined - or use an INIT boot APIC message otherwise:
+	 * Wake up a CPU in difference cases:
+	 * - Use the method in the APIC driver if it's defined
+	 * Otherwise,
+	 * - Use an INIT boot APIC message for APs or NMI for BSP.
 	 */
 	if (apic->wakeup_secondary_cpu)
 		boot_error = apic->wakeup_secondary_cpu(apicid, start_ip);
 	else
-		boot_error = wakeup_secondary_cpu_via_init(apicid, start_ip);
+		boot_error = wakeup_cpu_via_init_nmi(cpu, start_ip, apicid,
+						     &cpu0_nmi_registered);
 
 	if (!boot_error) {
 		/*
@@ -793,6 +860,13 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
 		 */
 		smpboot_restore_warm_reset_vector();
 	}
+	/*
+	 * Clean up the nmi handler. Do this after the callin and callout sync
+	 * to avoid impact of possible long unregister time.
+	 */
+	if (cpu0_nmi_registered)
+		unregister_nmi_handler(NMI_LOCAL, "wake_cpu0");
+
 	return boot_error;
 }
 
@@ -1037,6 +1111,11 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
 	 */
 	setup_local_APIC();
 
+	if (x2apic_mode)
+		cpu0_logical_apicid = apic_read(APIC_LDR);
+	else
+		cpu0_logical_apicid = GET_APIC_LOGICAL_ID(apic_read(APIC_LDR));
+
 	/*
 	 * Enable IO APIC before setting up error vector
 	 */
@@ -1264,6 +1343,14 @@ void play_dead_common(void)
 	local_irq_disable();
 }
 
+static bool wakeup_cpu0(void)
+{
+	if (smp_processor_id() == 0 && enable_start_cpu0)
+		return true;
+
+	return false;
+}
+
 /*
  * We need to flush the caches before going to sleep, lest we have
  * dirty data in our caches when we come back up.
@@ -1327,6 +1414,11 @@ static inline void mwait_play_dead(void)
 		__monitor(mwait_ptr, 0, 0);
 		mb();
 		__mwait(eax, 0);
+		/*
+		 * If NMI wants to wake up CPU0, start CPU0.
+		 */
+		if (wakeup_cpu0())
+			start_cpu0();
 	}
 }
 
@@ -1337,6 +1429,11 @@ static inline void hlt_play_dead(void)
 
 	while (1) {
 		native_halt();
+		/*
+		 * If NMI wants to wake up CPU0, start CPU0.
+		 */
+		if (wakeup_cpu0())
+			start_cpu0();
 	}
 }