[PATCH] x86/mce: Cover grading of AMD machine error checks

[Carlos Bilbao]

AMD's severity grading covers very few machine errors. In the graded cases
there are no user-readable messages, complicating debugging of critical
hardware errors.

Fix the above issues extending the current grading logic for AMD with cases
not previously considered and their corresponding messages.

Signed-off-by: Carlos Bilbao <carlos.bilbao@xxxxxxx>
---
 arch/x86/include/asm/mce.h         |   6 +
 arch/x86/kernel/cpu/mce/severity.c | 232 +++++++++++++++++++++++++----
 2 files changed, 205 insertions(+), 33 deletions(-)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index cc73061e7255..6b1ef40f8580 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -50,6 +50,12 @@
 #define MCI_STATUS_POISON	BIT_ULL(43)  /* access poisonous data */
 #define MCI_STATUS_SCRUB	BIT_ULL(40)  /* Error detected during scrub operation */
 
+/* AMD Error codes from PPR(s) section 3.1 Machine Check Architecture */
+#define ERRORCODE_T_MSK GENMASK(3, 2) /* Mask for transaction type bits */
+#define ERRORCODE_M_MSK GENMASK(7, 4) /* Mask for memory transaction type */
+#define ERRORCODE_T_DATA  0x4  /* Transaction type of error is Data */
+#define ERRORCODE_M_FETCH 0x50 /* Memory transaction type of error is Instruction Fetch */
+
 /*
  * McaX field if set indicates a given bank supports MCA extensions:
  *  - Deferred error interrupt type is specifiable by bank.
diff --git a/arch/x86/kernel/cpu/mce/severity.c b/arch/x86/kernel/cpu/mce/severity.c
index 1add86935349..764c6caf4bfe 100644
--- a/arch/x86/kernel/cpu/mce/severity.c
+++ b/arch/x86/kernel/cpu/mce/severity.c
@@ -327,59 +327,225 @@ static __always_inline int mce_severity_amd_smca(struct mce *m, enum context err
 }
 
 /*
- * See AMD Error Scope Hierarchy table in a newer BKDG. For example
- * 49125_15h_Models_30h-3Fh_BKDG.pdf, section "RAS Features"
+ * Evaluate the severity of a data load error for AMD systems, depending
+ * on the context in which the MCE happened.
  */
-static noinstr int mce_severity_amd(struct mce *m, struct pt_regs *regs, char **msg, bool is_excp)
+static inline int mce_grade_data_amd(enum context ctx, char **severity_msg)
 {
-	enum context ctx = error_context(m, regs);
+	WARN_ON(!severity_msg);
+
+	switch (ctx) {
+	case IN_USER:
+		*severity_msg = "Action required: data load error in user process";
+		return MCE_AR_SEVERITY;
+	case IN_KERNEL_RECOV:
+		*severity_msg = "Action required: data load in kernel recoverable area";
+		return MCE_AR_SEVERITY;
+	case IN_KERNEL:
+		*severity_msg = "Data load in unrecoverable area of kernel";
+		return MCE_PANIC_SEVERITY;
+	default:
+		*severity_msg = "Data load in unknown context";
+		return MCE_PANIC_SEVERITY;
+	}
+}
 
-	/* Processor Context Corrupt, no need to fumble too much, die! */
-	if (m->status & MCI_STATUS_PCC)
+/*
+ * Evaluate the severity of an instruction fetch error for AMD systems,
+ * depending on the context in which the MCE happened.
+ */
+static inline int mce_grade_fetch_amd(enum context ctx, char **severity_msg)
+{
+	WARN_ON(!severity_msg);
+
+	switch (ctx) {
+	case IN_USER:
+		*severity_msg = "Action required: instruction fetch in user process";
+		return MCE_AR_SEVERITY;
+	case IN_KERNEL_RECOV:
+		*severity_msg = "Instruction fetch in kernel recoverable area";
+#ifdef CONFIG_MEMORY_FAILURE
+		return MCE_AR_SEVERITY;
+#else /* !MCE_PANIC_SEVERITY */
 		return MCE_PANIC_SEVERITY;
+#endif
+	case IN_KERNEL:
+		*severity_msg = "Instruction fetch error in kernel";
+		return MCE_PANIC_SEVERITY;
+	default:
+		*severity_msg = "Instruction fetch error in unknown context";
+		return MCE_PANIC_SEVERITY;
+	}
+}
 
-	if (m->status & MCI_STATUS_UC) {
+/*
+ * Evaluate the severity of a memory poison error for AMD systems,
+ * depending on the context in which the MCE happened.
+ */
+static inline int mce_grade_poison_amd(enum context ctx, char **severity_msg)
+{
 
-		if (ctx == IN_KERNEL)
-			return MCE_PANIC_SEVERITY;
+	WARN_ON(!severity_msg);
+
+	switch (ctx) {
+	case IN_USER:
+		*severity_msg = "Attempt to consume poisoned data in user process";
+		return MCE_AR_SEVERITY;
+	case IN_KERNEL_RECOV:
+		*severity_msg = "Attempt to consume poisoned memory in kernel recoverable area";
+#ifdef CONFIG_MEMORY_FAILURE
+		return MCE_AR_SEVERITY;
+#else /* !CONFIG_MEMORY_FAILURE */
+		return MCE_PANIC_SEVERITY;
+#endif
+	case IN_KERNEL:
+		*severity_msg = "Attempt to consume poisoned data in kernel context";
+		return MCE_PANIC_SEVERITY;
+	default:
+		*severity_msg = "Poisoned data consumption in unknown context";
+		return MCE_PANIC_SEVERITY;
+	}
+}
+
+/*
+ * Evaluate the severity of deferred errors for AMD systems, for which only
+ * scrub error is interesting to notify an action requirement.
+ */
+static noinstr int mce_grade_deferred_amd(struct mce *m, enum context ctx, char **msg)
+{
+	int ret;
+
+	WARN_ON(!msg);
 
+	if (m->status & MCI_STATUS_SCRUB) {
+		ret = MCE_AR_SEVERITY;
+		*msg = "Action required: Error detected on a scrub operation";
+	} else {
 		/*
-		 * On older systems where overflow_recov flag is not present, we
-		 * should simply panic if an error overflow occurs. If
-		 * overflow_recov flag is present and set, then software can try
-		 * to at least kill process to prolong system operation.
+		 * deferred error: poll handler catches these and adds to mce_ring so
+		 * memory-failure can take recovery actions.
 		 */
-		if (mce_flags.overflow_recov) {
-			if (mce_flags.smca)
-				return mce_severity_amd_smca(m, ctx);
+		ret = MCE_DEFERRED_SEVERITY;
+		*msg = "Deferred";
+	}
 
-			/* kill current process */
-			return MCE_AR_SEVERITY;
+	return ret;
+}
+
+/*
+ * Evaluate the severity of an overflow error for AMD systems, dependent on
+ * the recoverable features available.
+ */
+static noinstr int mce_grade_overflow_amd(struct mce *m, enum context ctx, char **msg)
+{
+	int ret;
+
+	WARN_ON(!msg);
+
+	if (ctx == IN_KERNEL) {
+		*msg = "Uncorrectable error in kernel context";
+		return MCE_PANIC_SEVERITY;
+	}
+
+	/*
+	 * On older systems where overflow_recov flag is not present, we
+	 * should simply panic if an error overflow occurs. If
+	 * overflow_recov flag is present and set, then software can try
+	 * to at least kill process to prolong system operation.
+	 */
+	if (mce_flags.overflow_recov) {
+		*msg = "Uncorrected recoverable error";
+		if (mce_flags.smca) {
+			ret = mce_severity_amd_smca(m, ctx);
+			if (ret == MCE_PANIC_SEVERITY)
+				*msg = "Uncorrected unrecoverable error";
 		} else {
-			/* at least one error was not logged */
-			if (m->status & MCI_STATUS_OVER)
-				return MCE_PANIC_SEVERITY;
+			/* kill current process */
+			ret = MCE_AR_SEVERITY;
 		}
+		return ret;
+	}
 
-		/*
-		 * For any other case, return MCE_UC_SEVERITY so that we log the
-		 * error and exit #MC handler.
-		 */
-		return MCE_UC_SEVERITY;
+	/* at least one error was not logged */
+	if (m->status & MCI_STATUS_OVER) {
+		*msg = "Overflow uncorrected";
+		return MCE_PANIC_SEVERITY;
 	}
 
 	/*
-	 * deferred error: poll handler catches these and adds to mce_ring so
-	 * memory-failure can take recovery actions.
+	 * For any other case, return MCE_UC_SEVERITY so that we log the
+	 * error and exit #MC handler.
 	 */
-	if (m->status & MCI_STATUS_DEFERRED)
-		return MCE_DEFERRED_SEVERITY;
+	*msg = "Uncorrected overflow error";
+	return MCE_UC_SEVERITY;
+}
+
+/*
+ * See AMD PPR(s) section 3.1 Machine Check Architecture
+ */
+static noinstr int mce_severity_amd(struct mce *m, struct pt_regs *regs, char **msg, bool is_excp)
+{
+	enum context ctx = error_context(m, regs);
+	char *severity_msg;
+	int ret;
 
 	/*
-	 * corrected error: poll handler catches these and passes responsibility
-	 * of decoding the error to EDAC
+	 * Default return values. The poll handler catches these and passes
+	 * responsibility of decoding them to EDAC
 	 */
-	return MCE_KEEP_SEVERITY;
+	ret = MCE_KEEP_SEVERITY;
+	severity_msg = "Corrected error";
+
+	if (m->status & MCI_STATUS_DEFERRED) {
+		ret = mce_grade_deferred_amd(m, ctx, &severity_msg);
+		goto amd_severity;
+	}
+
+	/* If the UC bit is not set, the error has been corrected */
+	if (!(m->status & MCI_STATUS_UC)) {
+		ret = MCE_KEEP_SEVERITY;
+		severity_msg = "Corrected error";
+		goto amd_severity;
+	}
+
+	if (m->status & MCI_STATUS_POISON) {
+		ret = mce_grade_poison_amd(ctx, &severity_msg);
+		goto amd_severity;
+	}
+
+	/* Processor Context Corrupt, no need to fumble too much, die! */
+	if (m->status & MCI_STATUS_PCC) {
+		severity_msg = "Processor Context Corrupt";
+		ret = MCE_PANIC_SEVERITY;
+		goto amd_severity;
+	}
+
+	if ((m->status & ERRORCODE_T_MSK) == ERRORCODE_T_DATA) {
+		ret = mce_grade_data_amd(ctx, &severity_msg);
+		goto amd_severity;
+	}
+
+	if ((m->status & ERRORCODE_M_MSK) == ERRORCODE_M_FETCH) {
+		ret = mce_grade_fetch_amd(ctx, &severity_msg);
+		goto amd_severity;
+	}
+
+	if (m->status & MCI_STATUS_OVER) {
+		ret = mce_grade_overflow_amd(m, ctx, &severity_msg);
+		goto amd_severity;
+	}
+
+	if (ctx == IN_KERNEL) {
+		ret = MCE_PANIC_SEVERITY;
+		severity_msg = "Uncorrectable error in kernel context";
+	}
+
+amd_severity:
+
+	if (msg)
+		*msg = severity_msg;
+
+	return ret;
 }
 
 static noinstr int mce_severity_intel(struct mce *m, struct pt_regs *regs, char **msg, bool is_excp)

base-commit: 7f1b8e0d6360178e3527d4f14e6921c254a86035
-- 
2.27.0