We've been fighting a long running battle with the use
of per-cpu variables in early boot code on ia64. In
current code accessing them before cpu_init() has a
chance to initialize ar.k3 with the physical address
of the per-cpu page results in the system hanging.
This is the reason that CONFIG_PRINTK_TIME results in
a kernel that does not boot.
This patch fixes this by allocating the memory for the
per-cpu page in kernel .data segment and initializing
ar.k3 to point to it[1] in head.S before any C code has
the opportunity to access a per-cpu variable.
Life is a little complex because the SMP=n case uses the
__phys_per_cpu_start copy of the per cpu variables directly.
Tested with tiger_defconfig and generic_defconfig kernels
on Intel tiger system (to check both the contig.c and
discontig.c allocations). But I'd appreciate hearing
whether this works on a real NUMA system.
-Tony
[1] ar.k3 actually points at the physical address of the
*END* of the per-cpu page to make life easy for the MCA
code to use it in assembly code.
---
diff --git a/arch/ia64/kernel/head.S b/arch/ia64/kernel/head.S
index 41c7129..ae650f1 100644
--- a/arch/ia64/kernel/head.S
+++ b/arch/ia64/kernel/head.S
@@ -359,7 +359,18 @@ 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
+#ifndef CONFIG_SMP
+ mov r18=PERCPU_PAGE_SIZE
+ ;;
+ add r19=r19,r18
+#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
;;
diff --git a/arch/ia64/kernel/setup.c b/arch/ia64/kernel/setup.c
index 593279f..c27d5b2 100644
--- a/arch/ia64/kernel/setup.c
+++ b/arch/ia64/kernel/setup.c
@@ -927,17 +927,19 @@ cpu_init (void)
if (smp_processor_id() == 0) {
cpu_set(0, per_cpu(cpu_sibling_map, 0));
cpu_set(0, cpu_core_map[0]);
+ } else {
+ /*
+ * Set ar.k3 so that assembly code in MCA handler can compute
+ * physical addresses of per cpu variables with a simple:
+ * phys = ar.k3 + &per_cpu_var
+ * and the alt-dtlb-miss handler can set per-cpu mapping into
+ * the TLB when needed. head.S already did this for cpu0.
+ */
+ ia64_set_kr(IA64_KR_PER_CPU_DATA,
+ ia64_tpa(cpu_data) - (long) __per_cpu_start);
}
#endif
- /*
- * We set ar.k3 so that assembly code in MCA handler can compute
- * physical addresses of per cpu variables with a simple:
- * phys = ar.k3 + &per_cpu_var
- */
- ia64_set_kr(IA64_KR_PER_CPU_DATA,
- ia64_tpa(cpu_data) - (long) __per_cpu_start);
-
get_max_cacheline_size();
/*
diff --git a/arch/ia64/kernel/vmlinux.lds.S b/arch/ia64/kernel/vmlinux.lds.S
index 5a77206..de71da8 100644
--- a/arch/ia64/kernel/vmlinux.lds.S
+++ b/arch/ia64/kernel/vmlinux.lds.S
@@ -215,6 +215,9 @@ SECTIONS
/* Per-cpu data: */
percpu : { } :percpu
. = ALIGN(PERCPU_PAGE_SIZE);
+#ifdef CONFIG_SMP
+ . = . + PERCPU_PAGE_SIZE; /* cpu0 per-cpu space */
+#endif
__phys_per_cpu_start = .;
.data.percpu PERCPU_ADDR : AT(__phys_per_cpu_start - LOAD_OFFSET)
{
diff --git a/arch/ia64/mm/contig.c b/arch/ia64/mm/contig.c
index 798bf98..35ae83b 100644
--- a/arch/ia64/mm/contig.c
+++ b/arch/ia64/mm/contig.c
@@ -163,8 +163,15 @@ per_cpu_init (void)
* get_zeroed_page().
*/
if (first_time) {
+ void *cpu0_data = __phys_per_cpu_start - PERCPU_PAGE_SIZE;
+
first_time=0;
- for (cpu = 0; cpu < NR_CPUS; cpu++) {
+
+ memcpy(cpu0_data, __phys_per_cpu_start, __per_cpu_end - __per_cpu_start);
+ __per_cpu_offset[0] = (char *) cpu0_data - __per_cpu_start;
+ per_cpu(local_per_cpu_offset, 0) = __per_cpu_offset[0];
+
+ for (cpu = 1; cpu < NR_CPUS; cpu++) {
memcpy(cpu_data, __phys_per_cpu_start, __per_cpu_end - __per_cpu_start);
__per_cpu_offset[cpu] = (char *) cpu_data - __per_cpu_start;
cpu_data += PERCPU_PAGE_SIZE;
@@ -177,7 +184,7 @@ per_cpu_init (void)
static inline void
alloc_per_cpu_data(void)
{
- cpu_data = __alloc_bootmem(PERCPU_PAGE_SIZE * NR_CPUS,
+ cpu_data = __alloc_bootmem(PERCPU_PAGE_SIZE * NR_CPUS-1,
PERCPU_PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
}
#else
diff --git a/arch/ia64/mm/discontig.c b/arch/ia64/mm/discontig.c
index d83125e..7690710 100644
--- a/arch/ia64/mm/discontig.c
+++ b/arch/ia64/mm/discontig.c
@@ -143,7 +143,13 @@ static void *per_cpu_node_setup(void *cpu_data, int node)
int cpu;
for_each_possible_early_cpu(cpu) {
- if (node == node_cpuid[cpu].nid) {
+ if (cpu == 0) {
+ void *cpu0_data = __phys_per_cpu_start - PERCPU_PAGE_SIZE;
+ memcpy(cpu0_data, __phys_per_cpu_start,
+ __per_cpu_end - __per_cpu_start);
+ __per_cpu_offset[cpu] = (char*)cpu0_data -
+ __per_cpu_start;
+ } else if (node == node_cpuid[cpu].nid) {
memcpy(__va(cpu_data), __phys_per_cpu_start,
__per_cpu_end - __per_cpu_start);
__per_cpu_offset[cpu] = (char*)__va(cpu_data) -
--
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