[PATCH 4/8] x86/mce/AMD: Do not perform shared bank check for future processors

[Borislav Petkov]

From: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@xxxxxxx>

Fam17h and above should not require a check to see if a bank is shared
or not. For shared banks, there will always be only one core that has
visibility over the MSRs and only that particular core will be allowed
to write to the MSRs.

Fix the code to return early if we have Scalable MCA support. No change
in functionality for earlier processors.

Boris: Fold in fix from kbuild test robot for:

  arch/x86/kernel/cpu/mcheck/mce_amd.c:93:9-10: WARNING: return of 0/1 in function 'is_shared_bank' with return type bool
  Generated by: scripts/coccinelle/misc/boolreturn.cocci

Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@xxxxxxx>
Cc: linux-edac <linux-edac@xxxxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: x86-ml <x86@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1452901836-27632-3-git-send-email-Aravind.Gopalakrishnan@xxxxxxx
Signed-off-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
[ Boris: massage text. ]
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
 arch/x86/kernel/cpu/mcheck/mce_amd.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
index e99b15077e94..3068ce25dfa1 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
@@ -84,6 +84,13 @@ struct thresh_restart {
 
 static inline bool is_shared_bank(int bank)
 {
+	/*
+	 * Scalable MCA provides for only one core to have access to the MSRs of
+	 * a shared bank.
+	 */
+	if (mce_flags.smca)
+		return false;
+
 	/* Bank 4 is for northbridge reporting and is thus shared */
 	return (bank == 4);
 }
-- 
2.3.5