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

AMD's MCA Thresholding feature counts errors of all severity levels, 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.

[ bp: Simplify, convert comment to passive voice. ]

Fixes: 37d43acfd79f ("x86/mce/AMD: Redo error logging from APIC LVT interrupt handlers")
Signed-off-by: Yazen Ghannam <[e-mail]>
Signed-off-by: Borislav Petkov <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]

arch/x86/kernel/cpu/mce/amd.c

···
 	return status & MCI_STATUS_DEFERRED;
 }
 
+static bool _log_error_deferred(unsigned int bank, u32 misc)
+{
+	if (!_log_error_bank(bank, mca_msr_reg(bank, MCA_STATUS),
+			     mca_msr_reg(bank, MCA_ADDR), misc))
+		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 the deferred error was logged from MCA_STATUS. */
+	wrmsrl(MSR_AMD64_SMCA_MCx_DESTAT(bank), 0);
+	return true;
+}
+
 /*
  * We have three scenarios for checking for Deferred errors:
  *
···
  */
 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)
+	if (_log_error_deferred(bank, 0))
 		return;
-
-	/* Clear MCA_DESTAT if we logged the deferred error from MCA_STATUS. */
-	if (defrd) {
-		wrmsrl(MSR_AMD64_SMCA_MCx_DESTAT(bank), 0);
-		return;
-	}
 
 	/*
 	 * Only deferred errors are logged in MCA_DE{STAT,ADDR} so just check
···
 
 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)