arm: SMP CPU shutdown

For completeness, also implelent the CPU shutdown path.

Signed-off-by: Tim Deegan <tim@xen.org>
Committed-by: Ian Campbell <ian.campbell@citrix.com>

xen/arch/arm/domain.c

@@ -31,12 +31,10 @@ void idle_loop(void)
 {
     for ( ; ; )
     {
-        /* TODO
         if ( cpu_is_offline(smp_processor_id()) )
-           play_dead();
-           (*pm_idle)();
-           BUG();
-        */
+            stop_cpu();
+
+        /* TODO: (*pm_idle)(); */
         do_tasklet();
         do_softirq();
     }

xen/arch/arm/gic.c

@@ -239,6 +239,11 @@ static void __cpuinit gic_cpu_init(void)
     GICC[GICC_CTLR] = GICC_CTL_ENABLE|GICC_CTL_EOI;    /* Turn on delivery */
 }
 
+static void gic_cpu_disable(void)
+{
+    GICC[GICC_CTLR] = 0;
+}
+
 static void __cpuinit gic_hyp_init(void)
 {
     uint32_t vtr;
@@ -250,6 +255,11 @@ static void __cpuinit gic_hyp_init(void)
     GICH[GICH_MISR] = GICH_MISR_EOI;
 }
 
+static void __cpuinit gic_hyp_disable(void)
+{
+    GICH[GICH_HCR] = 0;
+}
+
 /* Set up the GIC */
 int __init gic_init(void)
 {
@@ -286,6 +296,15 @@ void __cpuinit gic_init_secondary_cpu(void)
     spin_unlock(&gic.lock);
 }
 
+/* Shut down the per-CPU GIC interface */
+void gic_disable_cpu(void)
+{
+    spin_lock(&gic.lock);
+    gic_cpu_disable();
+    gic_hyp_disable();
+    spin_unlock(&gic.lock);
+}
+
 void gic_route_irqs(void)
 {
     /* XXX should get these from DT */

xen/arch/arm/gic.h

@@ -142,6 +142,8 @@ extern void gic_interrupt(struct cpu_user_regs *regs, int is_fiq);
 extern int gic_init(void);
 /* Bring up a secondary CPU's per-CPU GIC interface */
 extern void gic_init_secondary_cpu(void);
+/* Take down a CPU's per-CPU GIC interface */
+extern void gic_disable_cpu(void);
 /* setup the gic virtual interface for a guest */
 extern void gicv_setup(struct domain *d);
 #endif

xen/arch/arm/smpboot.c

@@ -18,6 +18,7 @@
 
 #include <xen/cpu.h>
 #include <xen/cpumask.h>
+#include <xen/delay.h>
 #include <xen/errno.h>
 #include <xen/init.h>
 #include <xen/mm.h>
@@ -57,6 +58,7 @@ smp_prepare_cpus (unsigned int max_cpus)
 
 /* Shared state for coordinating CPU bringup */
 unsigned long smp_up_cpu = 0;
+static bool_t cpu_is_dead = 0;
 
 /* Boot the current CPU */
 void __cpuinit start_secondary(unsigned long boot_phys_offset,
@@ -97,8 +99,35 @@ void __cpuinit start_secondary(unsigned long boot_phys_offset,
 /* Shut down the current CPU */
 void __cpu_disable(void)
 {
-    /* TODO: take down timers, GIC, &c. */
+    unsigned int cpu = get_processor_id();
+
+    local_irq_disable();
+    gic_disable_cpu();
+    /* Allow any queued timer interrupts to get serviced */
+    local_irq_enable();
+    mdelay(1);
+    local_irq_disable();
+
+    /* It's now safe to remove this processor from the online map */
+    cpumask_clear_cpu(cpu, &cpu_online_map);
+
+    if ( cpu_disable_scheduler(cpu) )
         BUG();
+    mb();
+
+    /* Return to caller; eventually the IPI mechanism will unwind and the 
+     * scheduler will drop to the idle loop, which will call stop_cpu(). */
+}
+
+void stop_cpu(void)
+{
+    local_irq_disable();
+    cpu_is_dead = 1;
+    /* Make sure the write happens before we sleep forever */
+    dsb();
+    isb();
+    while ( 1 ) 
+        asm volatile("wfi");
 }
 
 /* Bring up a remote CPU */
@@ -124,8 +153,19 @@ int __cpu_up(unsigned int cpu)
 /* Wait for a remote CPU to die */
 void __cpu_die(unsigned int cpu)
 {
-    /* TODO: interlock with __cpu_disable */
-    BUG();
+    unsigned int i = 0;
+
+    while ( !cpu_is_dead )
+    {
+        mdelay(100);
+        cpu_relax();
+        process_pending_softirqs();
+        if ( (++i % 10) == 0 )
+            printk(KERN_ERR "CPU %u still not dead...\n", cpu);
+        mb();
+    }
+    cpu_is_dead = 0;
+    mb();
 }
 
 

xen/include/asm-arm/smp.h

@@ -14,6 +14,8 @@ DECLARE_PER_CPU(cpumask_var_t, cpu_core_mask);
 
 #define raw_smp_processor_id() (get_processor_id())
 
+extern void stop_cpu(void);
+
 #endif
 /*
  * Local variables: