[tip:ras/urgent] x86/mce/AMD: Give a name to MCA bank 3 when accessed with legacy MSRs

[tip-bot for Yazen Ghannam]

Commit-ID:  7cc5ad0d4aec505bee7f49696867668aa3889195
Gitweb:     http://git.kernel.org/tip/7cc5ad0d4aec505bee7f49696867668aa3889195
Author:     Yazen Ghannam <yazen.ghannam@xxxxxxx>
AuthorDate: Thu, 30 Mar 2017 13:17:14 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 31 Mar 2017 08:10:09 +0200

x86/mce/AMD: Give a name to MCA bank 3 when accessed with legacy MSRs

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:

  WARNING: CPU: 26 PID: 1 at lib/kobject.c:210 kobject_add_internal
  kobject: (ffff88085bb256c0): attempted to be registered with empty name!
  ...
  Call Trace:
   dump_stack()
   warn_slowpath_common()
   warn_slowpath_fmt()
   kobject_add_internal()
   kobject_add()
   kobject_create_and_add()
   threshold_create_device()
   threshold_init_device()
   do_one_initcall()
   kernel_init_freeable()
   kernel_init()
   ret_from_fork()

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.

Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 3.10..
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-edac <linux-edac@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170330111713.cnkbloffyouxg52e@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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 524cc57..6e4a047 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
@@ -60,7 +60,7 @@ static const char * const th_names[] = {
 	"load_store",
 	"insn_fetch",
 	"combined_unit",
-	"",
+	"decode_unit",
 	"northbridge",
 	"execution_unit",
 };