[PATCH for.38] x86, numa: Fix numa_emulation code with node0 without RAM

[PATCH for.38] x86, numa: Fix numa_emulation code with node0 without RAM

[Yinghai Lu]

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:

[    0.076025] ------------[ cut here ]------------
[    0.080004] kernel BUG at arch/x86/mm/numa_64.c:788!
[    0.080004] invalid opcode: 0000 [#1] SMP 
[    0.080004] last sysfs file: 
[    0.080004] CPU 0 
[    0.080004] Modules linked in:
[    0.080004] 
[    0.080004] Pid: 0, comm: swapper Not tainted 2.6.38-rc6-yh-00212-g3e1f235 #1 Sun Microsystems     Sun Fire X4240/Sun Fire X4240
[    0.080004] RIP: 0010:[<ffffffff81cd1d8c>]  [<ffffffff81cd1d8c>] numa_add_cpu+0x8a/0x156
...
[    0.080004] Call Trace:
[    0.080004]  [<ffffffff81ccd1cd>] identify_cpu+0x2d7/0x2df
[    0.080004]  [<ffffffff827e13e9>] identify_boot_cpu+0x10/0x30
[    0.080004]  [<ffffffff827e15f3>] check_bugs+0x9/0x2d
[    0.080004]  [<ffffffff827d9bcb>] start_kernel+0x3bf/0x3d9
[    0.080004]  [<ffffffff827d92a6>] x86_64_start_reservations+0xb6/0xba
[    0.080004]  [<ffffffff827d93a1>] x86_64_start_kernel+0xf7/0xfe
[    0.080004] Code: 74 06 48 8d 04 90 eb 0f 48 c7 c0 10 d9 00 00 48 03 04 d5 50 e1 5f 82 8b 00 83 f8 ff 74 0d 0f a3 05 7a f9 92 00 19 d2 85 d2 75 02 <0f> 0b 48 98 31 db 48 8b 04 c5 d0 ec 5f 82 48 8b 90 90 af 00 00 

need to used early_cpu_to_node directly, because cpu_to_apicid and apicid_to_node
 will return node0 that is not onlined.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 arch/x86/mm/numa_64.c |    6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

Index: linux-2.6/arch/x86/mm/numa_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/numa_64.c
+++ linux-2.6/arch/x86/mm/numa_64.c
@@ -780,11 +780,7 @@ void __cpuinit numa_add_cpu(int cpu)
 	int physnid;
 	int nid = NUMA_NO_NODE;
 
-	apicid = early_per_cpu(x86_cpu_to_apicid, cpu);
-	if (apicid != BAD_APICID)
-		nid = apicid_to_node[apicid];
-	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));
 
 	/*

Re: [PATCH for.38] x86, numa: Fix numa_emulation code with node0 without RAM

[Tejun Heo]

On Wed, Mar 02, 2011 at 03:14:58PM -0800, Yinghai Lu wrote:
> 
> 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:
> 
> [    0.076025] ------------[ cut here ]------------
> [    0.080004] kernel BUG at arch/x86/mm/numa_64.c:788!
> [    0.080004] invalid opcode: 0000 [#1] SMP 
> [    0.080004] last sysfs file: 
> [    0.080004] CPU 0 
> [    0.080004] Modules linked in:
> [    0.080004] 
> [    0.080004] Pid: 0, comm: swapper Not tainted 2.6.38-rc6-yh-00212-g3e1f235 #1 Sun Microsystems     Sun Fire X4240/Sun Fire X4240
> [    0.080004] RIP: 0010:[<ffffffff81cd1d8c>]  [<ffffffff81cd1d8c>] numa_add_cpu+0x8a/0x156
> ...
> [    0.080004] Call Trace:
> [    0.080004]  [<ffffffff81ccd1cd>] identify_cpu+0x2d7/0x2df
> [    0.080004]  [<ffffffff827e13e9>] identify_boot_cpu+0x10/0x30
> [    0.080004]  [<ffffffff827e15f3>] check_bugs+0x9/0x2d
> [    0.080004]  [<ffffffff827d9bcb>] start_kernel+0x3bf/0x3d9
> [    0.080004]  [<ffffffff827d92a6>] x86_64_start_reservations+0xb6/0xba
> [    0.080004]  [<ffffffff827d93a1>] x86_64_start_kernel+0xf7/0xfe
> [    0.080004] Code: 74 06 48 8d 04 90 eb 0f 48 c7 c0 10 d9 00 00 48 03 04 d5 50 e1 5f 82 8b 00 83 f8 ff 74 0d 0f a3 05 7a f9 92 00 19 d2 85 d2 75 02 <0f> 0b 48 98 31 db 48 8b 04 c5 d0 ec 5f 82 48 8b 90 90 af 00 00 
> 
> need to used early_cpu_to_node directly, because cpu_to_apicid and apicid_to_node
>  will return node0 that is not onlined.
> 
> Signed-off-by: Yinghai Lu <yinghai@kernel.org>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

[tip:x86/urgent] x86, numa: Fix numa_emulation code with memory-less node0

[tip-bot for Yinghai Lu]

Commit-ID:  3b28cf32cc32594710590685ee478f697ed4f328
Gitweb:     http://git.kernel.org/tip/3b28cf32cc32594710590685ee478f697ed4f328
Author:     Yinghai Lu <yinghai@kernel.org>
AuthorDate: Wed, 2 Mar 2011 15:14:58 -0800
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 4 Mar 2011 15:20:19 +0100

x86, numa: Fix numa_emulation code with memory-less node0

This crash happens on a system that does not have RAM on node0.

When numa_emulation is compiled in, and:

 1. we boot the system without numa=fake...
 2. or we boot the system with numa=fake=128 to make emulation fail

we will get:

[    0.076025] ------------[ cut here ]------------
[    0.080004] kernel BUG at arch/x86/mm/numa_64.c:788!
[    0.080004] invalid opcode: 0000 [#1] SMP
[...]

need to use early_cpu_to_node() directly, because cpu_to_apicid
and apicid_to_node will return node0 that is not onlined.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
LKML-Reference: <4D6ECF72.5010308@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/mm/numa_64.c |    6 +-----
 1 files changed, 1 insertions(+), 5 deletions(-)

diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
index 95ea155..1337c51 100644
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -780,11 +780,7 @@ void __cpuinit numa_add_cpu(int cpu)
 	int physnid;
 	int nid = NUMA_NO_NODE;
 
-	apicid = early_per_cpu(x86_cpu_to_apicid, cpu);
-	if (apicid != BAD_APICID)
-		nid = apicid_to_node[apicid];
-	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));
 
 	/*