[PATCH] Re: [Patch] MCE,APEI: Don't enable CMCI when Firmware First mode is set in

[Naveen N. Rao]

HEST for corrected machine checks

Here's a patch that implements this technique. If the firmware advertises
support for firmware first mode in the CMC structure, we disable CMCI and
polling for all the MCA banks listed in the CMC structure.

- Naveen

Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/mce.h             |    3 ++
 arch/x86/kernel/cpu/mcheck/mce_intel.c |   38 +++++++++++++++++++++++++++++++
 drivers/acpi/apei/hest.c               |   39 ++++++++++++++++++++++++++++++++
 3 files changed, 80 insertions(+)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index fa5f71e..9c91683 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -188,6 +188,9 @@ extern void register_mce_write_callback(ssize_t (*)(struct file *filp,
 				    const char __user *ubuf,
 				    size_t usize, loff_t *off));
 
+/* Disable CMCI/polling for MCA bank claimed by firmware */
+extern void mce_disable_bank(int bank);
+
 /*
  * Exception handler
  */
diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c
index ae1697c..bc0307d 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -26,6 +26,9 @@
 
 static DEFINE_PER_CPU(mce_banks_t, mce_banks_owned);
 
+/* MCA banks controlled through firmware first */
+static mce_banks_t mce_banks_disabled;
+
 /*
  * cmci_discover_lock protects against parallel discovery attempts
  * which could race against each other.
@@ -191,6 +194,10 @@ static void cmci_discover(int banks)
 		if (test_bit(i, owned))
 			continue;
 
+		/* Skip banks in firmware first mode */
+		if (test_bit(i, mce_banks_disabled))
+			continue;
+
 		rdmsrl(MSR_IA32_MCx_CTL2(i), val);
 
 		/* Already owned by someone else? */
@@ -315,6 +322,37 @@ void cmci_reenable(void)
 		cmci_discover(banks);
 }
 
+static void cmci_disable_bank(void *arg)
+{
+	int banks;
+	unsigned long flags;
+	u64 val;
+	int bank = *((int *)arg);
+
+	/* Ensure we don't poll this bank */
+	__clear_bit(bank, __get_cpu_var(mce_poll_banks));
+
+	if (!cmci_supported(&banks))
+		return;
+
+	raw_spin_lock_irqsave(&cmci_discover_lock, flags);
+
+	/* Disable CMCI */
+	rdmsrl(MSR_IA32_MCx_CTL2(bank), val);
+	val &= ~MCI_CTL2_CMCI_EN;
+	wrmsrl(MSR_IA32_MCx_CTL2(bank), val);
+
+	__clear_bit(bank, __get_cpu_var(mce_banks_owned));
+
+	raw_spin_unlock_irqrestore(&cmci_discover_lock, flags);
+}
+
+void mce_disable_bank(int bank)
+{
+	set_bit(bank, mce_banks_disabled);
+	on_each_cpu(cmci_disable_bank, &bank, 1);
+}
+
 static void intel_init_cmci(void)
 {
 	int banks;
diff --git a/drivers/acpi/apei/hest.c b/drivers/acpi/apei/hest.c
index f5ef5d5..765d8bf 100644
--- a/drivers/acpi/apei/hest.c
+++ b/drivers/acpi/apei/hest.c
@@ -36,6 +36,7 @@
 #include <linux/io.h>
 #include <linux/platform_device.h>
 #include <acpi/apei.h>
+#include <asm/mce.h>
 
 #include "apei-internal.h"
 
@@ -121,6 +122,42 @@ int apei_hest_parse(apei_hest_func_t func, void *data)
 }
 EXPORT_SYMBOL_GPL(apei_hest_parse);
 
+/*
+ * Check if firmware advertises firmware first mode. We need FF bit to be set
+ * along with a set of MC banks which work in FF mode.
+ */
+static int __init hest_parse_cmc(struct acpi_hest_header *hest_hdr, void *data)
+{
+	int i;
+	struct acpi_hest_ia_corrected *cmc;
+	struct acpi_hest_ia_error_bank *mc_bank;
+
+	if (hest_hdr->type != ACPI_HEST_TYPE_IA32_CORRECTED_CHECK)
+		return 0;
+
+	if (!((struct acpi_hest_generic *)hest_hdr)->enabled)
+		return 0;
+
+	cmc = (struct acpi_hest_ia_corrected *)hest_hdr;
+	if (!(cmc->flags & ACPI_HEST_FIRMWARE_FIRST))
+		return 0;
+
+	/*
+	 * We expect HEST to provide a list of MC banks that
+	 * report errors through firmware first mode.
+	 */
+	if (cmc->num_hardware_banks <= 0)
+		return 0;
+
+	pr_info("HEST: Enabling Firmware First mode for corrected errors\n");
+
+	mc_bank = (struct acpi_hest_ia_error_bank *)(cmc + 1);
+	for (i = 0; i < cmc->num_hardware_banks; i++, mc_bank++)
+		mce_disable_bank(mc_bank->bank_number);
+
+	return 0;
+}
+
 struct ghes_arr {
 	struct platform_device **ghes_devs;
 	unsigned int count;
@@ -227,6 +264,8 @@ void __init acpi_hest_init(void)
 		goto err;
 	}
 
+	apei_hest_parse(hest_parse_cmc, NULL);
+
 	if (!ghes_disable) {
 		rc = apei_hest_parse(hest_parse_ghes_count, &ghes_count);
 		if (rc)

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