[IA64] support for cpu0 removal

here is the BSP removal support for IA64. Its pretty much the same thing that
was released a while back, but has your feedback incorporated.

- Removed CONFIG_BSP_REMOVE_WORKAROUND and associated cmdline param
- Fixed compile issue with sn2/zx1 due to a undefined fix_b0_for_bsp
- some formatting nits (whitespace etc)

This has been tested on tiger and long back by alex on hp systems as well.

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/Kconfig

@@ -272,6 +272,25 @@ config SCHED_SMT
 	  Intel IA64 chips with MultiThreading at a cost of slightly increased
 	  overhead in some places. If unsure say N here.
 
+config PERMIT_BSP_REMOVE
+	bool "Support removal of Bootstrap Processor"
+	depends on HOTPLUG_CPU
+	default n
+	---help---
+	Say Y here if your platform SAL will support removal of BSP with HOTPLUG_CPU
+	support. 
+
+config FORCE_CPEI_RETARGET
+	bool "Force assumption that CPEI can be re-targetted"
+	depends on PERMIT_BSP_REMOVE
+	default n
+	---help---
+	Say Y if you need to force the assumption that CPEI can be re-targetted to
+	any cpu in the system. This hint is available via ACPI 3.0 specifications.
+	Tiger4 systems are capable of re-directing CPEI to any CPU other than BSP.
+	This option it useful to enable this feature on older BIOS's as well.
+	You can also enable this by using boot command line option force_cpei=1.
+
 config PREEMPT
 	bool "Preemptible Kernel"
         help

arch/ia64/configs/tiger_defconfig

@@ -114,6 +114,8 @@ CONFIG_FORCE_MAX_ZONEORDER=17
 CONFIG_SMP=y
 CONFIG_NR_CPUS=4
 CONFIG_HOTPLUG_CPU=y
+CONFIG_PERMIT_BSP_REMOVE=y
+CONFIG_FORCE_CPEI_RETARGET=y
 # CONFIG_SCHED_SMT is not set
 # CONFIG_PREEMPT is not set
 CONFIG_SELECT_MEMORY_MODEL=y

arch/ia64/kernel/acpi.c

@@ -287,16 +287,20 @@ acpi_parse_plat_int_src(acpi_table_entry_header * header,
 unsigned int can_cpei_retarget(void)
 {
 	extern int cpe_vector;
+	extern unsigned int force_cpei_retarget;
 
 	/*
 	 * Only if CPEI is supported and the override flag
 	 * is present, otherwise return that its re-targettable
 	 * if we are in polling mode.
 	 */
-	if (cpe_vector > 0 && !acpi_cpei_override)
-		return 0;
-	else
-		return 1;
+	if (cpe_vector > 0) {
+		if (acpi_cpei_override || force_cpei_retarget)
+			return 1;
+		else
+			return 0;
+	}
+	return 1;
 }
 
 unsigned int is_cpu_cpei_target(unsigned int cpu)

arch/ia64/kernel/iosapic.c

@@ -631,6 +631,7 @@ get_target_cpu (unsigned int gsi, int vector)
 {
 #ifdef CONFIG_SMP
 	static int cpu = -1;
+	extern int cpe_vector;
 
 	/*
 	 * In case of vector shared by multiple RTEs, all RTEs that
@@ -653,6 +654,11 @@ get_target_cpu (unsigned int gsi, int vector)
 	if (!cpu_online(smp_processor_id()))
 		return cpu_physical_id(smp_processor_id());
 
+#ifdef CONFIG_ACPI
+		if (cpe_vector > 0 && vector == IA64_CPEP_VECTOR)
+			return get_cpei_target_cpu();
+#endif
+
 #ifdef CONFIG_NUMA
 	{
 		int num_cpus, cpu_index, iosapic_index, numa_cpu, i = 0;

arch/ia64/kernel/irq.c

@@ -163,8 +163,19 @@ void fixup_irqs(void)
 {
 	unsigned int irq;
 	extern void ia64_process_pending_intr(void);
+	extern void ia64_disable_timer(void);
+	extern volatile int time_keeper_id;
+
+	ia64_disable_timer();
+
+	/*
+	 * Find a new timesync master
+	 */
+	if (smp_processor_id() == time_keeper_id) {
+		time_keeper_id = first_cpu(cpu_online_map);
+		printk ("CPU %d is now promoted to time-keeper master\n", time_keeper_id);
+	}
 
-	ia64_set_itv(1<<16);
 	/*
 	 * Phase 1: Locate irq's bound to this cpu and
 	 * relocate them for cpu removal.

arch/ia64/kernel/mca.c

@@ -289,6 +289,7 @@ ia64_mca_log_sal_error_record(int sal_info_type)
 #ifdef CONFIG_ACPI
 
 int cpe_vector = -1;
+int ia64_cpe_irq = -1;
 
 static irqreturn_t
 ia64_mca_cpe_int_handler (int cpe_irq, void *arg, struct pt_regs *ptregs)
@@ -1444,11 +1445,13 @@ void __devinit
 ia64_mca_cpu_init(void *cpu_data)
 {
 	void *pal_vaddr;
+	static int first_time = 1;
 
-	if (smp_processor_id() == 0) {
+	if (first_time) {
 		void *mca_data;
 		int cpu;
 
+		first_time = 0;
 		mca_data = alloc_bootmem(sizeof(struct ia64_mca_cpu)
 					 * NR_CPUS + KERNEL_STACK_SIZE);
 		mca_data = (void *)(((unsigned long)mca_data +
@@ -1704,6 +1707,7 @@ ia64_mca_late_init(void)
 					desc = irq_descp(irq);
 					desc->status |= IRQ_PER_CPU;
 					setup_irq(irq, &mca_cpe_irqaction);
+					ia64_cpe_irq = irq;
 				}
 			ia64_mca_register_cpev(cpe_vector);
 			IA64_MCA_DEBUG("%s: CPEI/P setup and enabled.\n", __FUNCTION__);

arch/ia64/kernel/perfmon.c

@@ -6718,6 +6718,7 @@ __initcall(pfm_init);
 void
 pfm_init_percpu (void)
 {
+	static int first_time=1;
 	/*
 	 * make sure no measurement is active
 	 * (may inherit programmed PMCs from EFI).
@@ -6730,8 +6731,10 @@ pfm_init_percpu (void)
 	 */
 	pfm_unfreeze_pmu();
 
-	if (smp_processor_id() == 0)
+	if (first_time) {
 		register_percpu_irq(IA64_PERFMON_VECTOR, &perfmon_irqaction);
+		first_time=0;
+	}
 
 	ia64_setreg(_IA64_REG_CR_PMV, IA64_PERFMON_VECTOR);
 	ia64_srlz_d();

arch/ia64/kernel/smpboot.c

@@ -70,6 +70,12 @@
 #endif
 
 #ifdef CONFIG_HOTPLUG_CPU
+#ifdef CONFIG_PERMIT_BSP_REMOVE
+#define bsp_remove_ok	1
+#else
+#define bsp_remove_ok	0
+#endif
+
 /*
  * Store all idle threads, this can be reused instead of creating
  * a new thread. Also avoids complicated thread destroy functionality
@@ -104,7 +110,7 @@ struct sal_to_os_boot *sal_state_for_booting_cpu = &sal_boot_rendez_state[0];
 /*
  * ITC synchronization related stuff:
  */
-#define MASTER	0
+#define MASTER	(0)
 #define SLAVE	(SMP_CACHE_BYTES/8)
 
 #define NUM_ROUNDS	64	/* magic value */
@@ -151,6 +157,27 @@ char __initdata no_int_routing;
 
 unsigned char smp_int_redirect; /* are INT and IPI redirectable by the chipset? */
 
+#ifdef CONFIG_FORCE_CPEI_RETARGET
+#define CPEI_OVERRIDE_DEFAULT	(1)
+#else
+#define CPEI_OVERRIDE_DEFAULT	(0)
+#endif
+
+unsigned int force_cpei_retarget = CPEI_OVERRIDE_DEFAULT;
+
+static int __init
+cmdl_force_cpei(char *str)
+{
+	int value=0;
+
+	get_option (&str, &value);
+	force_cpei_retarget = value;
+
+	return 1;
+}
+
+__setup("force_cpei=", cmdl_force_cpei);
+
 static int __init
 nointroute (char *str)
 {
@@ -161,6 +188,27 @@ nointroute (char *str)
 
 __setup("nointroute", nointroute);
 
+static void fix_b0_for_bsp(void)
+{
+#ifdef CONFIG_HOTPLUG_CPU
+	int cpuid;
+	static int fix_bsp_b0 = 1;
+
+	cpuid = smp_processor_id();
+
+	/*
+	 * Cache the b0 value on the first AP that comes up
+	 */
+	if (!(fix_bsp_b0 && cpuid))
+		return;
+
+	sal_boot_rendez_state[0].br[0] = sal_boot_rendez_state[cpuid].br[0];
+	printk ("Fixed BSP b0 value from CPU %d\n", cpuid);
+
+	fix_bsp_b0 = 0;
+#endif
+}
+
 void
 sync_master (void *arg)
 {
@@ -327,22 +375,26 @@ smp_setup_percpu_timer (void)
 static void __devinit
 smp_callin (void)
 {
-	int cpuid, phys_id;
+	int cpuid, phys_id, itc_master;
 	extern void ia64_init_itm(void);
+	extern volatile int time_keeper_id;
 
 #ifdef CONFIG_PERFMON
 	extern void pfm_init_percpu(void);
 #endif
 
 	cpuid = smp_processor_id();
 	phys_id = hard_smp_processor_id();
+	itc_master = time_keeper_id;
 
 	if (cpu_online(cpuid)) {
 		printk(KERN_ERR "huh, phys CPU#0x%x, CPU#0x%x already present??\n",
 		       phys_id, cpuid);
 		BUG();
 	}
 
+	fix_b0_for_bsp();
+
 	lock_ipi_calllock();
 	cpu_set(cpuid, cpu_online_map);
 	unlock_ipi_calllock();
@@ -365,8 +417,8 @@ smp_callin (void)
 		 * calls spin_unlock_bh(), which calls spin_unlock_bh(), which calls
 		 * local_bh_enable(), which bugs out if irqs are not enabled...
 		 */
-		Dprintk("Going to syncup ITC with BP.\n");
-		ia64_sync_itc(0);
+		Dprintk("Going to syncup ITC with ITC Master.\n");
+		ia64_sync_itc(itc_master);
 	}
 
 	/*
@@ -638,6 +690,47 @@ remove_siblinginfo(int cpu)
 }
 
 extern void fixup_irqs(void);
+
+int migrate_platform_irqs(unsigned int cpu)
+{
+	int new_cpei_cpu;
+	irq_desc_t *desc = NULL;
+	cpumask_t 	mask;
+	int 		retval = 0;
+
+	/*
+	 * dont permit CPEI target to removed.
+	 */
+	if (cpe_vector > 0 && is_cpu_cpei_target(cpu)) {
+		printk ("CPU (%d) is CPEI Target\n", cpu);
+		if (can_cpei_retarget()) {
+			/*
+			 * Now re-target the CPEI to a different processor
+			 */
+			new_cpei_cpu = any_online_cpu(cpu_online_map);
+			mask = cpumask_of_cpu(new_cpei_cpu);
+			set_cpei_target_cpu(new_cpei_cpu);
+			desc = irq_descp(ia64_cpe_irq);
+			/*
+			 * Switch for now, immediatly, we need to do fake intr
+			 * as other interrupts, but need to study CPEI behaviour with
+			 * polling before making changes.
+			 */
+			if (desc) {
+				desc->handler->disable(ia64_cpe_irq);
+				desc->handler->set_affinity(ia64_cpe_irq, mask);
+				desc->handler->enable(ia64_cpe_irq);
+				printk ("Re-targetting CPEI to cpu %d\n", new_cpei_cpu);
+			}
+		}
+		if (!desc) {
+			printk ("Unable to retarget CPEI, offline cpu [%d] failed\n", cpu);
+			retval = -EBUSY;
+		}
+	}
+	return retval;
+}
+
 /* must be called with cpucontrol mutex held */
 int __cpu_disable(void)
 {
@@ -646,8 +739,17 @@ int __cpu_disable(void)
 	/*
 	 * dont permit boot processor for now
 	 */
-	if (cpu == 0)
-		return -EBUSY;
+	if (cpu == 0 && !bsp_remove_ok) {
+		printk ("Your platform does not support removal of BSP\n");
+		return (-EBUSY);
+	}
+
+	cpu_clear(cpu, cpu_online_map);
+
+	if (migrate_platform_irqs(cpu)) {
+		cpu_set(cpu, cpu_online_map);
+		return (-EBUSY);
+	}
 
 	remove_siblinginfo(cpu);
 	cpu_clear(cpu, cpu_online_map);

arch/ia64/kernel/time.c

@@ -32,7 +32,7 @@
 
 extern unsigned long wall_jiffies;
 
-#define TIME_KEEPER_ID	0	/* smp_processor_id() of time-keeper */
+volatile int time_keeper_id = 0; /* smp_processor_id() of time-keeper */
 
 #ifdef CONFIG_IA64_DEBUG_IRQ
 
@@ -71,7 +71,7 @@ timer_interrupt (int irq, void *dev_id, struct pt_regs *regs)
 
 		new_itm += local_cpu_data->itm_delta;
 
-		if (smp_processor_id() == TIME_KEEPER_ID) {
+		if (smp_processor_id() == time_keeper_id) {
 			/*
 			 * Here we are in the timer irq handler. We have irqs locally
 			 * disabled, but we don't know if the timer_bh is running on
@@ -236,6 +236,11 @@ static struct irqaction timer_irqaction = {
 	.name =		"timer"
 };
 
+void __devinit ia64_disable_timer(void)
+{
+	ia64_set_itv(1 << 16);
+}
+
 void __init
 time_init (void)
 {

arch/ia64/mm/contig.c

@@ -181,13 +181,15 @@ per_cpu_init (void)
 {
 	void *cpu_data;
 	int cpu;
+	static int first_time=1;
 
 	/*
 	 * get_free_pages() cannot be used before cpu_init() done.  BSP
 	 * allocates "NR_CPUS" pages for all CPUs to avoid that AP calls
 	 * get_zeroed_page().
 	 */
-	if (smp_processor_id() == 0) {
+	if (first_time) {
+		first_time=0;
 		cpu_data = __alloc_bootmem(PERCPU_PAGE_SIZE * NR_CPUS,
 					   PERCPU_PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
 		for (cpu = 0; cpu < NR_CPUS; cpu++) {