[PATCH] x86/mce: Rework DFR handling flow

[Yazen Ghannam]

Add a flag to poll for Deferred errors similar to MCP_UC for
uncorrectable errors. This will do checks specific to deferred errors
and fallback to common UC/CE checks otherwise.

Also, clear the MCA_DESTAT register at the end of the handler rather
than the beginning.

Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
---
 arch/x86/include/asm/mce.h     |  1 +
 arch/x86/kernel/cpu/mce/amd.c  | 13 ++++++++----
 arch/x86/kernel/cpu/mce/core.c | 36 ++++++++++++++++++++--------------
 3 files changed, 31 insertions(+), 19 deletions(-)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 1cfbfff0be3f..9652fc11860d 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -299,6 +299,7 @@ enum mcp_flags {
 	MCP_TIMESTAMP	= BIT(0),	/* log time stamp */
 	MCP_UC		= BIT(1),	/* log uncorrected errors */
 	MCP_QUEUE_LOG	= BIT(2),	/* only queue to genpool */
+	MCP_DFR		= BIT(3),	/* log deferred errors */
 };
 
 void machine_check_poll(enum mcp_flags flags, mce_banks_t *b);
diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
index 9b746080351f..83fad4503b1c 100644
--- a/arch/x86/kernel/cpu/mce/amd.c
+++ b/arch/x86/kernel/cpu/mce/amd.c
@@ -839,7 +839,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_deferred_error)
 /* APIC interrupt handler for deferred errors */
 static void amd_deferred_error_interrupt(void)
 {
-	machine_check_poll(MCP_TIMESTAMP, &this_cpu_ptr(&mce_amd_data)->dfr_intr_banks);
+	machine_check_poll(MCP_TIMESTAMP | MCP_DFR, &this_cpu_ptr(&mce_amd_data)->dfr_intr_banks);
 }
 
 void mce_amd_handle_storm(unsigned int bank, bool on)
@@ -865,10 +865,15 @@ void amd_clear_bank(struct mce *m)
 {
 	amd_reset_thr_limit(m->bank);
 
-	if (m->kflags & MCE_CHECK_DFR_REGS)
+	/* Clear MCA_DESTAT for all deferred errors even those logged in MCA_STATUS. */
+	if (m->status & MCI_STATUS_DEFERRED)
 		mce_wrmsrq(MSR_AMD64_SMCA_MCx_DESTAT(m->bank), 0);
-	else
-		mce_wrmsrq(mca_msr_reg(m->bank, MCA_STATUS), 0);
+
+	/* Don't clear MCA_STATUS if MCA_DESTAT was used exclusively. */
+	if (m->kflags & MCE_CHECK_DFR_REGS)
+		return;
+
+	mce_wrmsrq(mca_msr_reg(m->bank, MCA_STATUS), 0);
 }
 
 /*
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index e2d51609d2cb..960efee4be3e 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -731,27 +731,26 @@ static bool smca_should_log_poll_error(enum mcp_flags flags, struct mce_hw_err *
 	struct mce *m = &err->m;
 
 	/*
-	 * If this is a deferred error found in MCA_STATUS, then clear
-	 * the redundant data from the MCA_DESTAT register.
+	 * If the MCA_STATUS register has a deferred error, then continue using it as
+	 * the status register.
+	 *
+	 * MCA_DESTAT will be cleared at the end of the handler.
 	 */
-	if (m->status & MCI_STATUS_VAL) {
-		if (m->status & MCI_STATUS_DEFERRED)
-			mce_wrmsrq(MSR_AMD64_SMCA_MCx_DESTAT(m->bank), 0);
-
+	if ((m->status & MCI_STATUS_VAL) && (m->status & MCI_STATUS_DEFERRED))
 		return true;
-	}
 
 	/*
-	 * If the MCA_DESTAT register has valid data, then use
-	 * it as the status register.
+	 * If the MCA_DESTAT register has a deferred error, then use it instead.
+	 *
+	 * MCA_STATUS will not be cleared at the end of the handler.
 	 */
 	m->status = mce_rdmsrq(MSR_AMD64_SMCA_MCx_DESTAT(m->bank));
+	if ((m->status & MCI_STATUS_VAL) && (m->status & MCI_STATUS_DEFERRED)) {
+		m->kflags |= MCE_CHECK_DFR_REGS;
+		return true;
+	}
 
-	if (!(m->status & MCI_STATUS_VAL))
-		return false;
-
-	m->kflags |= MCE_CHECK_DFR_REGS;
-	return true;
+	return false;
 }
 
 /*
@@ -780,13 +779,17 @@ static bool should_log_poll_error(enum mcp_flags flags, struct mce_hw_err *err)
 {
 	struct mce *m = &err->m;
 
-	if (mce_flags.smca)
+	if (flags & MCP_DFR)
 		return smca_should_log_poll_error(flags, err);
 
 	/* If this entry is not valid, ignore it. */
 	if (!(m->status & MCI_STATUS_VAL))
 		return false;
 
+	/* Ignore deferred errors if not looking for them (MCP_DFR not set). */
+	if (m->status & MCI_STATUS_DEFERRED)
+		return false;
+
 	/*
 	 * If we are logging everything (at CPU online) or this
 	 * is a corrected error, then we must log it.
@@ -1924,6 +1927,9 @@ static void __mcheck_cpu_init_prepare_banks(void)
 
 		bitmap_fill(all_banks, MAX_NR_BANKS);
 		machine_check_poll(MCP_UC | MCP_QUEUE_LOG, &all_banks);
+
+		if (mce_flags.smca)
+			machine_check_poll(MCP_DFR | MCP_QUEUE_LOG, &all_banks);
 	}
 
 	for (i = 0; i < this_cpu_read(mce_num_banks); i++) {
-- 
2.51.0