["RFC PATCH" 1/2] powerpc/mm: Fix node look up with numa=off boot

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

If we boot with numa=off, we need to make sure we return NUMA_NO_NODE when
looking up associativity details of resources. Without this, we hit crash
like below

BUG: Unable to handle kernel data access at 0x40000000008
Faulting instruction address: 0xc000000008f31704
cpu 0x1b: Vector: 380 (Data SLB Access) at [c00000000b9bb320]
    pc: c000000008f31704: _raw_spin_lock+0x14/0x100
    lr: c0000000083f41fc: ____cache_alloc_node+0x5c/0x290
    sp: c00000000b9bb5b0
   msr: 800000010280b033
   dar: 40000000008
  current = 0xc00000000b9a2700
  paca    = 0xc00000000a740c00   irqmask: 0x03   irq_happened: 0x01
    pid   = 1, comm = swapper/27
Linux version 5.2.0-rc4-00925-g74e188c620b1 (root@linux-d8ip) (gcc version 7.4.1 20190424 [gcc-7-branch revision 270538] (SUSE Linux)) #34 SMP Sat Jun 29 00:41:02 EDT 2019
enter ? for help
[link register   ] c0000000083f41fc ____cache_alloc_node+0x5c/0x290
[c00000000b9bb5b0] 0000000000000dc0 (unreliable)
[c00000000b9bb5f0] c0000000083f48c8 kmem_cache_alloc_node_trace+0x138/0x360
[c00000000b9bb670] c000000008aa789c devres_alloc_node+0x4c/0xa0
[c00000000b9bb6a0] c000000008337218 devm_memremap+0x58/0x130
[c00000000b9bb6f0] c000000008aed00c devm_nsio_enable+0xdc/0x170
[c00000000b9bb780] c000000008af3b6c nd_pmem_probe+0x4c/0x180
[c00000000b9bb7b0] c000000008ad84cc nvdimm_bus_probe+0xac/0x260
[c00000000b9bb840] c000000008aa0628 really_probe+0x148/0x500
[c00000000b9bb8d0] c000000008aa0d7c driver_probe_device+0x19c/0x1d0
[c00000000b9bb950] c000000008aa11bc device_driver_attach+0xcc/0x100
[c00000000b9bb990] c000000008aa12ec __driver_attach+0xfc/0x1e0
[c00000000b9bba10] c000000008a9d0a4 bus_for_each_dev+0xb4/0x130
[c00000000b9bba70] c000000008a9fc04 driver_attach+0x34/0x50
[c00000000b9bba90] c000000008a9f118 bus_add_driver+0x1d8/0x300
[c00000000b9bbb20] c000000008aa2358 driver_register+0x98/0x1a0
[c00000000b9bbb90] c000000008ad7e6c __nd_driver_register+0x5c/0x100
[c00000000b9bbbf0] c0000000093efbac nd_pmem_driver_init+0x34/0x48
[c00000000b9bbc10] c0000000080106c0 do_one_initcall+0x60/0x2d0
[c00000000b9bbce0] c00000000938463c kernel_init_freeable+0x384/0x48c
[c00000000b9bbdb0] c000000008010a5c kernel_init+0x2c/0x160
[c00000000b9bbe20] c00000000800ba54 ret_from_kernel_thread+0x5c/0x68

Reported-and-debugged-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 arch/powerpc/mm/numa.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 917904d2fe97..f6d68baeaa96 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -212,7 +212,7 @@ static int associativity_to_nid(const __be32 *associativity)
 {
 	int nid = NUMA_NO_NODE;
 
-	if (min_common_depth == -1)
+	if (min_common_depth == -1 || !numa_enabled)
 		goto out;
 
 	if (of_read_number(associativity, 1) >= min_common_depth)
@@ -416,10 +416,14 @@ static int of_get_assoc_arrays(struct assoc_arrays *aa)
 static int of_drconf_to_nid_single(struct drmem_lmb *lmb)
 {
 	struct assoc_arrays aa = { .arrays = NULL };
+	/* is that correct? */
 	int default_nid = 0;
 	int nid = default_nid;
 	int rc, index;
 
+	if (!numa_enabled)
+		return NUMA_NO_NODE;
+
 	rc = of_get_assoc_arrays(&aa);
 	if (rc)
 		return default_nid;
@@ -808,7 +812,7 @@ static void __init find_possible_nodes(void)
 	struct device_node *rtas;
 	u32 numnodes, i;
 
-	if (min_common_depth <= 0)
+	if (min_common_depth <= 0 || !numa_enabled)
 		return;
 
 	rtas = of_find_node_by_path("/rtas");
-- 
2.21.0