[PATCH] x86/mce/AMD: Give a name to MCA bank 3 to use with legacy MSRs

[Yazen Ghannam]

From: Yazen Ghannam <yazen.ghannam@xxxxxxx>

MCA bank 3 is reserved on systems pre-Fam17h, so it didn't have a name.
However, MCA bank 3 is defined on Fam17h systems and can be accessed using
legacy MSRs. Without a name we get a stack trace on Fam17h systems when
trying to register sysfs files for bank 3 on kernels that don't recognize
Scalable MCA.

Call MCA bank 3 "decode_unit" since this is what it represents on Fam17h.
This will allow kernels without SMCA support to see this bank on Fam17h+
and prevent the stack trace. This will not affect older systems since this
bank is reserved on them, i.e. it'll be ignored.

Tested on AMD Fam15h and Fam17h systems.

 WARNING: CPU: 26 PID: 1 at lib/kobject.c:210 kobject_add_internal+0x23e/0x340()
 kobject: (ffff88085bb256c0): attempted to be registered with empty name!
 ...
 Call Trace:
  [<ffffffff8138fc83>] dump_stack+0x63/0x90
  [<ffffffff810769b6>] warn_slowpath_common+0x86/0xc0
  [<ffffffff81076a3c>] warn_slowpath_fmt+0x4c/0x50
  [<ffffffff8139290e>] ? kobject_add_internal+0x18e/0x340
  [<ffffffff81187f82>] ? kfree_const+0x22/0x30
  [<ffffffff813929be>] kobject_add_internal+0x23e/0x340
  [<ffffffff81187f82>] ? kfree_const+0x22/0x30
  [<ffffffff81392cb8>] kobject_add+0x68/0xb0
  [<ffffffff81392d33>] kobject_create_and_add+0x33/0x70
  [<ffffffff81043c27>] threshold_create_device+0x107/0x350
  [<ffffffff81d7e7aa>] ? mcheck_vendor_init_severity+0x1a/0x1a
  [<ffffffff81d7e7df>] threshold_init_device+0x35/0x4d
  [<ffffffff81002123>] do_one_initcall+0xb3/0x1d0
  [<ffffffff81d6e0f0>] kernel_init_freeable+0x163/0x1f0
  [<ffffffff8176e0f0>] ? rest_init+0x80/0x80
  [<ffffffff8176e0fe>] kernel_init+0xe/0xe0
  [<ffffffff8177a7cf>] ret_from_fork+0x3f/0x70
  [<ffffffff8176e0f0>] ? rest_init+0x80/0x80

Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 3.10..
---
 arch/x86/kernel/cpu/mcheck/mce_amd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
index d3e5be8..c82befc 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
@@ -62,7 +62,7 @@ static const char * const th_names[] = {
 	"load_store",
 	"insn_fetch",
 	"combined_unit",
-	"",
+	"decode_unit",
 	"northbridge",
 	"execution_unit",
 };
-- 
2.7.4