powerpc/book3e: initialize crit/mc/dbg kernel stack pointers

We already allocated critical/machine/debug check exceptions, but
we also should initialize those associated kernel stack pointers
for use by special exceptions in the PACA.
Signed-off-by: NTiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: NScott Wood <scottwood@freescale.com>

arch/powerpc/kernel/setup_64.c

@@ -552,14 +552,20 @@ static void __init irqstack_early_init(void)
 static void __init exc_lvl_early_init(void)
 {
 	unsigned int i;
+	unsigned long sp;
 
 	for_each_possible_cpu(i) {
-		critirq_ctx[i] = (struct thread_info *)
-			__va(memblock_alloc(THREAD_SIZE, THREAD_SIZE));
-		dbgirq_ctx[i] = (struct thread_info *)
-			__va(memblock_alloc(THREAD_SIZE, THREAD_SIZE));
-		mcheckirq_ctx[i] = (struct thread_info *)
-			__va(memblock_alloc(THREAD_SIZE, THREAD_SIZE));
+		sp = memblock_alloc(THREAD_SIZE, THREAD_SIZE);
+		critirq_ctx[i] = (struct thread_info *)__va(sp);
+		paca[i].crit_kstack = __va(sp + THREAD_SIZE);
+
+		sp = memblock_alloc(THREAD_SIZE, THREAD_SIZE);
+		dbgirq_ctx[i] = (struct thread_info *)__va(sp);
+		paca[i].dbg_kstack = __va(sp + THREAD_SIZE);
+
+		sp = memblock_alloc(THREAD_SIZE, THREAD_SIZE);
+		mcheckirq_ctx[i] = (struct thread_info *)__va(sp);
+		paca[i].mc_kstack = __va(sp + THREAD_SIZE);
 	}
 
 	if (cpu_has_feature(CPU_FTR_DEBUG_LVL_EXC))