[PATCH 2/2] x86/mce: Report only DRAM ECC as memory errors on AMD systems

[Yazen Ghannam]

From: Yazen Ghannam <yazen.ghannam@xxxxxxx>

The MCA_STATUS[ErrorCodeExt] field is very bank type specific. We currently
check if the ErrorCodeExt value is 0x0 or 0x8 in mce_is_memory_error(), but
we don't check the bank. This means that we could flag non-memory errors as
memory errors.

We know that we want to flag DRAM ECC errors as memory errors, so let's do
those cases first. We can add more cases later when needed.

Check that bank type is UMC and xec is 0 on SMCA systems.

Check that bank is 4 (Northbridge) and xec is 8 on legacy systems.

Define a wrapper function in mce_amd.c so we can use SMCA enums.

Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
---
 arch/x86/include/asm/mce.h           |  2 ++
 arch/x86/kernel/cpu/mcheck/mce.c     |  4 +---
 arch/x86/kernel/cpu/mcheck/mce_amd.c | 11 +++++++++++
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 9ab8bf32e61c..7b1cc4d1710c 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -377,6 +377,7 @@ extern struct smca_bank smca_banks[MAX_NR_BANKS];
 
 extern const char *smca_get_long_name(enum smca_bank_types t);
 extern unsigned int smca_get_bank_type(struct mce *m);
+extern bool amd_mce_is_memory_error(struct mce *m);
 
 extern int mce_threshold_create_device(unsigned int cpu);
 extern int mce_threshold_remove_device(unsigned int cpu);
@@ -385,6 +386,7 @@ extern int mce_threshold_remove_device(unsigned int cpu);
 
 static inline int mce_threshold_create_device(unsigned int cpu) { return 0; };
 static inline int mce_threshold_remove_device(unsigned int cpu) { return 0; };
+static inline bool amd_mce_is_memory_error(struct mce *m) { return false; };
 
 #endif
 
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index b1d616d08eee..321c7a80be66 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -503,10 +503,8 @@ static int mce_usable_address(struct mce *m)
 bool mce_is_memory_error(struct mce *m)
 {
 	if (m->cpuvendor == X86_VENDOR_AMD) {
-		/* ErrCodeExt[20:16] */
-		u8 xec = (m->status >> 16) & 0x1f;
+		return amd_mce_is_memory_error(m);
 
-		return (xec == 0x0 || xec == 0x8);
 	} else if (m->cpuvendor == X86_VENDOR_INTEL) {
 		/*
 		 * Intel SDM Volume 3B - 15.9.2 Compound Error Codes
diff --git a/arch/x86/kernel/cpu/mcheck/mce_amd.c b/arch/x86/kernel/cpu/mcheck/mce_amd.c
index bc0510a4f6c0..b2f016bd1de5 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_amd.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_amd.c
@@ -751,6 +751,17 @@ int umc_normaddr_to_sysaddr(u64 norm_addr, u16 nid, u8 umc, u64 *sys_addr)
 }
 EXPORT_SYMBOL_GPL(umc_normaddr_to_sysaddr);
 
+bool amd_mce_is_memory_error(struct mce *m)
+{
+	/* ErrCodeExt[20:16] */
+	u8 xec = (m->status >> 16) & 0x1f;
+
+	if (mce_flags.smca)
+		return (smca_get_bank_type(m) == SMCA_UMC && xec == 0x0);
+
+	return (m->bank == 4 && xec == 0x8);
+}
+
 static void __log_error(unsigned int bank, u64 status, u64 addr, u64 misc)
 {
 	struct mce m;
-- 
2.14.1