x86, numa: Fix numa_emulation code with node0 without RAM

On one system that does not have RAM on node0.

when numa_emulation is compiled in, and
1. boot system without numa=fake...
2. or boot system with numa=fake=128 to make emulation fail

will get:

[    0.092026] ------------[ cut here ]------------
[    0.096005] kernel BUG at arch/x86/mm/numa_emulation.c:439!
[    0.096005] invalid opcode: 0000 [#1] SMP 
[    0.096005] last sysfs file: 
[    0.096005] CPU 0 
[    0.096005] Modules linked in:
[    0.096005] 
[    0.096005] Pid: 0, comm: swapper Not tainted 2.6.38-rc6-tip-yh-03869-gcb0491d-dirty #684 Sun Microsystems     Sun Fire X4240/Sun Fire X4240
[    0.096005] RIP: 0010:[<ffffffff81cdc65b>]  [<ffffffff81cdc65b>] numa_add_cpu+0x56/0xcf
[    0.096005] RSP: 0000:ffffffff82437ed8  EFLAGS: 00010246
...
[    0.096005] Call Trace:
[    0.096005]  [<ffffffff81cd7931>] identify_cpu+0x2d7/0x2df
[    0.096005]  [<ffffffff827e54fa>] identify_boot_cpu+0x10/0x30
[    0.096005]  [<ffffffff827e5704>] check_bugs+0x9/0x2d
[    0.096005]  [<ffffffff827dceda>] start_kernel+0x3d7/0x3f1
[    0.096005]  [<ffffffff827dc2cc>] x86_64_start_reservations+0x9c/0xa0
[    0.096005]  [<ffffffff827dc4ad>] x86_64_start_kernel+0x1dd/0x1e8
[    0.096005] Code: 74 06 48 8d 04 90 eb 0f 48 c7 c0 30 d9 00 00 48 03 04 d5 90 0f 60 82 8b 00 83 f8 ff 74 0d 0f a3 05 8b 7e 92 00 19 d2 85 d2 75 02 <0f> 0b 48 98 be 00 01 00 00 48 c7 c7 e0 44 60 82 44 8b 2c 85 e0 
[    0.096005] RIP  [<ffffffff81cdc65b>] numa_add_cpu+0x56/0xcf
[    0.096005]  RSP <ffffffff82437ed8>
[    0.096026] ---[ end trace a7919e7f17c0a725 ]---

need to used early_cpu_to_node directly, because numa_cpu_node() will return node0 that is not onlined.

index aeecea9..75b31dc 100644
@@ -417,9 +417,7 @@ void __cpuinit numa_add_cpu(int cpu)
 {
 	int physnid, nid;
 
-	nid = numa_cpu_node(cpu);
-	if (nid == NUMA_NO_NODE)
-		nid = early_cpu_to_node(cpu);
+	nid = early_cpu_to_node(cpu);
 	BUG_ON(nid == NUMA_NO_NODE || !node_online(nid));
 
 	physnid = emu_nid_to_phys[nid];

Thanks.

tejun

The Acked-by was for the other patch for .38. I applied this one to x86/mm.

Thanks.

tejun