[PATCH] x86/MCE/AMD: Clear DFR errors found in THR handler

[Yazen Ghannam]

AMD's MCA Thresholding feature counts errors of all severites not just
correctable errors. If a deferred error causes the threshold limit to be
reached (it was the error that caused the overflow), then both a
deferred error interrupt and a thresholding interrupt will be triggered.

The order of the interrupts is not guaranteed. If the threshold
interrupt handler is executed first, then it will clear MCA_STATUS for
the error. It will not check or clear MCA_DESTAT which also holds a copy
of the deferred error. When the deferred error interrupt handler runs it
will not find an error in MCA_STATUS, but it will find the error in
MCA_DESTAT. This will cause two errors to be logged.

Check for deferred errors when handling a threshold interrupt. If a bank
contains a deferred error, then clear the bank's MCA_DESTAT register.

Define a new helper function to do the deferred error check and clearing
of MCA_DESTAT.

Fixes: 37d43acfd79f ("x86/mce/AMD: Redo error logging from APIC LVT interrupt handlers")
Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
 arch/x86/kernel/cpu/mce/amd.c | 37 +++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index 1c87501e0fa3..ab1145cf8328 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -788,6 +788,28 @@ _log_error_bank(unsigned int bank, u32 msr_stat, u32 msr_addr, u64 misc)
 	return status & MCI_STATUS_DEFERRED;
 }
 
+static bool _log_error_deferred(unsigned int bank, u32 misc)
+{
+	bool defrd;
+
+	defrd = _log_error_bank(bank, mca_msr_reg(bank, MCA_STATUS),
+				mca_msr_reg(bank, MCA_ADDR), misc);
+
+	if (!defrd)
+		return false;
+
+	/*
+	 * Non-SMCA systems don't have MCA_DESTAT/MCA_DEADDR registers.
+	 * Return true here to avoid accessing these registers.
+	 */
+	if (!mce_flags.smca)
+		return true;
+
+	/* Clear MCA_DESTAT if we logged the deferred error from MCA_STATUS. */
+	wrmsrl(MSR_AMD64_SMCA_MCx_DESTAT(bank), 0);
+	return true;
+}
+
 /*
  * We have three scenarios for checking for Deferred errors:
  *
@@ -799,19 +821,8 @@ _log_error_bank(unsigned int bank, u32 msr_stat, u32 msr_addr, u64 misc)
  */
 static void log_error_deferred(unsigned int bank)
 {
-	bool defrd;
-
-	defrd = _log_error_bank(bank, mca_msr_reg(bank, MCA_STATUS),
-				mca_msr_reg(bank, MCA_ADDR), 0);
-
-	if (!mce_flags.smca)
-		return;
-
-	/* Clear MCA_DESTAT if we logged the deferred error from MCA_STATUS. */
-	if (defrd) {
-		wrmsrl(MSR_AMD64_SMCA_MCx_DESTAT(bank), 0);
+	if (_log_error_deferred(bank, 0))
 		return;
-	}
 
 	/*
 	 * Only deferred errors are logged in MCA_DE{STAT,ADDR} so just check
@@ -832,7 +843,7 @@ static void amd_deferred_error_interrupt(void)
 
 static void log_error_thresholding(unsigned int bank, u64 misc)
 {
-	_log_error_bank(bank, mca_msr_reg(bank, MCA_STATUS), mca_msr_reg(bank, MCA_ADDR), misc);
+	_log_error_deferred(bank, misc);
 }
 
 static void log_and_reset_block(struct threshold_block *block)
-- 
2.25.1