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Subject[PATCH v8 04/12] x86, hotplug: Support functions for CPU0 online/offline
Date
From: Fenghua Yu <fenghua.yu@intel.com>

Add smp_store_boot_cpu_info() to store cpu info for BSP during boot time.

Now smp_store_cpu_info() stores cpu info for bringing up BSP or AP after
it's offline.

Continue to online CPU0 in native_cpu_up().

Continue to offline CPU0 in native_cpu_disable().

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
---
arch/x86/include/asm/smp.h | 1 +
arch/x86/kernel/smpboot.c | 38 ++++++++++++++++++--------------------
2 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 4f19a15..b073aae 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -166,6 +166,7 @@ void native_send_call_func_ipi(const struct cpumask *mask);
void native_send_call_func_single_ipi(int cpu);
void x86_idle_thread_init(unsigned int cpu, struct task_struct *idle);

+void smp_store_boot_cpu_info(void);
void smp_store_cpu_info(int id);
#define cpu_physical_id(cpu) per_cpu(x86_cpu_to_apicid, cpu)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index c80a33b..c297907 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -125,8 +125,8 @@ EXPORT_PER_CPU_SYMBOL(cpu_info);
atomic_t init_deasserted;

/*
- * Report back to the Boot Processor.
- * Running on AP.
+ * Report back to the Boot Processor during boot time or to the caller processor
+ * during CPU online.
*/
static void __cpuinit smp_callin(void)
{
@@ -279,19 +279,30 @@ notrace static void __cpuinit start_secondary(void *unused)
cpu_idle();
}

+void __init smp_store_boot_cpu_info(void)
+{
+ int id = 0; /* CPU 0 */
+ struct cpuinfo_x86 *c = &cpu_data(id);
+
+ *c = boot_cpu_data;
+ c->cpu_index = id;
+}
+
/*
* The bootstrap kernel entry code has set these up. Save them for
* a given CPU
*/
-
void __cpuinit smp_store_cpu_info(int id)
{
struct cpuinfo_x86 *c = &cpu_data(id);

*c = boot_cpu_data;
c->cpu_index = id;
- if (id != 0)
- identify_secondary_cpu(c);
+ /*
+ * During boot time, CPU0 has this setup already. Save the info when
+ * bringing up AP or offlined CPU0.
+ */
+ identify_secondary_cpu(c);
}

static bool __cpuinit
@@ -795,7 +806,7 @@ int __cpuinit native_cpu_up(unsigned int cpu, struct task_struct *tidle)

pr_debug("++++++++++++++++++++=_---CPU UP %u\n", cpu);

- if (apicid == BAD_APICID || apicid == boot_cpu_physical_apicid ||
+ if (apicid == BAD_APICID ||
!physid_isset(apicid, phys_cpu_present_map) ||
!apic->apic_id_valid(apicid)) {
pr_err("%s: bad cpu %d\n", __func__, cpu);
@@ -990,7 +1001,7 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
/*
* Setup boot CPU information
*/
- smp_store_cpu_info(0); /* Final full version of the data */
+ smp_store_boot_cpu_info(); /* Final full version of the data */
cpumask_copy(cpu_callin_mask, cpumask_of(0));
mb();

@@ -1214,19 +1225,6 @@ void cpu_disable_common(void)

int native_cpu_disable(void)
{
- int cpu = smp_processor_id();
-
- /*
- * Perhaps use cpufreq to drop frequency, but that could go
- * into generic code.
- *
- * We won't take down the boot processor on i386 due to some
- * interrupts only being able to be serviced by the BSP.
- * Especially so if we're not using an IOAPIC -zwane
- */
- if (cpu == 0)
- return -EBUSY;
-
clear_local_APIC();

cpu_disable_common();
--
1.7.2


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