[IA64] Ensure cpu0 can access per-cpu variables in early boot code

ia64 handles per-cpu variables a litle differently from other architectures
in that it maps the physical memory allocated for each cpu at a constant
virtual address (0xffffffffffff0000). This mapping is not enabled until
the architecture specific cpu_init() function is run, which causes problems
since some generic code is run before this point. In particular when
CONFIG_PRINTK_TIME is enabled, the boot cpu will trap on the access to
per-cpu memory at the first printk() call so the boot will fail without
the kernel printing anything to the console.

Fix this by allocating percpu memory for cpu0 in the kernel data section
and doing all initialization to enable percpu access in head.S before
calling any generic code.

Other cpus must take care not to access per-cpu variables too early, but
their code path from start_secondary() to cpu_init() is all in arch/ia64

Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 25 insertions, 1 deletions

diff --git a/arch/ia64/kernel/head.S b/arch/ia64/kernel/head.S
index 41c712917ff7..8bdea8eb62e3 100644
--- a/arch/ia64/kernel/head.S
+++ b/arch/ia64/kernel/head.S
@@ -359,7 +359,31 @@ start_ap:
 	mov ar.rsc=0		// place RSE in enforced lazy mode
 	;;
 	loadrs			// clear the dirty partition
-	mov IA64_KR(PER_CPU_DATA)=r0	// clear physical per-CPU base
+	movl r19=__phys_per_cpu_start
+	mov r18=PERCPU_PAGE_SIZE
+	;;
+#ifndef CONFIG_SMP
+	add r19=r19,r18
+	;;
+#else
+(isAP)	br.few 2f
+	mov r20=r19
+	sub r19=r19,r18
+	;;
+	shr.u r18=r18,3
+1:
+	ld8 r21=[r20],8;;
+	st8[r19]=r21,8
+	adds r18=-1,r18;;
+	cmp4.lt p7,p6=0,r18
+(p7)	br.cond.dptk.few 1b
+2:
+#endif
+	tpa r19=r19
+	;;
+	.pred.rel.mutex isBP,isAP
+(isBP)	mov IA64_KR(PER_CPU_DATA)=r19	// per-CPU base for cpu0
+(isAP)	mov IA64_KR(PER_CPU_DATA)=r0	// clear physical per-CPU base
 	;;
 	mov ar.bspstore=r2	// establish the new RSE stack
 	;;