x86/mce: Provide boot argument to honour bios-set CMCI threshold

The ACPI spec doesn't provide for a way for the bios to pass down
recommended thresholds to the OS on a _per-bank_ basis. This patch adds
a new boot option, which if passed, tells Linux to use CMCI thresholds
set by the bios.

As fail-safe, we initialize threshold to 1 if some banks have not been
initialized by the bios and warn the user.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

4 files changed, 50 insertions, 3 deletions

diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt
index c54b4f503e2a..de38429beb71 100644
--- a/Documentation/x86/x86_64/boot-options.txt
+++ b/Documentation/x86/x86_64/boot-options.txt
@@ -50,6 +50,13 @@ Machine check
                 monarchtimeout:
                 Sets the time in us to wait for other CPUs on machine checks. 0
                 to disable.
+   mce=bios_cmci_threshold
+                Don't overwrite the bios-set CMCI threshold. This boot option
+                prevents Linux from overwriting the CMCI threshold set by the
+                bios. Without this option, Linux always sets the CMCI
+                threshold to 1. Enabling this may make memory predictive failure
+                analysis less effective if the bios sets thresholds for memory
+                errors since we will not see details for all errors.
 
    nomce (for compatibility with i386): same as mce=off
 
diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index ccaf7c581c8f..54d73b1f00a0 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -161,6 +161,7 @@ DECLARE_PER_CPU(struct device *, mce_device);
 #ifdef CONFIG_X86_MCE_INTEL
 extern int mce_cmci_disabled;
 extern int mce_ignore_ce;
+extern int mce_bios_cmci_threshold;
 void mce_intel_feature_init(struct cpuinfo_x86 *c);
 void cmci_clear(void);
 void cmci_reenable(void);
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index c311122ea838..29e87d3b2843 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -83,6 +83,7 @@ static int			mce_dont_log_ce		__read_mostly;
 int                             mce_cmci_disabled       __read_mostly;
 int                             mce_ignore_ce           __read_mostly;
 int                             mce_ser                 __read_mostly;
+int                             mce_bios_cmci_threshold __read_mostly;
 
 struct mce_bank                *mce_banks               __read_mostly;
 
@@ -1946,6 +1947,7 @@ static struct miscdevice mce_chrdev_device = {
  *      check, or 0 to not wait
  * mce=bootlog Log MCEs from before booting. Disabled by default on AMD.
  * mce=nobootlog Don't log MCEs from before booting.
+ * mce=bios_cmci_threshold Don't program the CMCI threshold
  */
 static int __init mcheck_enable(char *str)
 {
@@ -1965,6 +1967,8 @@ static int __init mcheck_enable(char *str)
                 mce_ignore_ce = 1;
         else if (!strcmp(str, "bootlog") || !strcmp(str, "nobootlog"))
                 mce_bootlog = (str[0] == 'b');
+        else if (!strcmp(str, "bios_cmci_threshold"))
+                mce_bios_cmci_threshold = 1;
         else if (isdigit(str[0])) {
                 get_option(&str, &tolerant);
                 if (*str == ',') {
@@ -2205,6 +2209,11 @@ static struct dev_ext_attribute dev_attr_cmci_disabled = {
         &mce_cmci_disabled
 };
 
+static struct dev_ext_attribute dev_attr_bios_cmci_threshold = {
+        __ATTR(bios_cmci_threshold, 0444, device_show_int, NULL),
+        &mce_bios_cmci_threshold
+};
+
 static struct device_attribute *mce_device_attrs[] = {
         &dev_attr_tolerant.attr,
         &dev_attr_check_interval.attr,
@@ -2213,6 +2222,7 @@ static struct device_attribute *mce_device_attrs[] = {
         &dev_attr_dont_log_ce.attr,
         &dev_attr_ignore_ce.attr,
         &dev_attr_cmci_disabled.attr,
+        &dev_attr_bios_cmci_threshold.attr,
         NULL
 };
 
diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c
index 098386fed48e..5f88abf07e9c 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -181,10 +181,12 @@ static void cmci_discover(int banks)
         unsigned long *owned = (void *)&__get_cpu_var(mce_banks_owned);
         unsigned long flags;
         int i;
+        int bios_wrong_thresh = 0;
 
         raw_spin_lock_irqsave(&cmci_discover_lock, flags);
         for (i = 0; i < banks; i++) {
                 u64 val;
+                int bios_zero_thresh = 0;
 
                 if (test_bit(i, owned))
                         continue;
@@ -198,8 +200,20 @@ static void cmci_discover(int banks)
                         continue;
                 }
 
-                val &= ~MCI_CTL2_CMCI_THRESHOLD_MASK;
-                val |= MCI_CTL2_CMCI_EN | CMCI_THRESHOLD;
+                if (!mce_bios_cmci_threshold) {
+                        val &= ~MCI_CTL2_CMCI_THRESHOLD_MASK;
+                        val |= CMCI_THRESHOLD;
+                } else if (!(val & MCI_CTL2_CMCI_THRESHOLD_MASK)) {
+                        /*
+                         * If bios_cmci_threshold boot option was specified
+                         * but the threshold is zero, we'll try to initialize
+                         * it to 1.
+                         */
+                        bios_zero_thresh = 1;
+                        val |= CMCI_THRESHOLD;
+                }
+
+                val |= MCI_CTL2_CMCI_EN;
                 wrmsrl(MSR_IA32_MCx_CTL2(i), val);
                 rdmsrl(MSR_IA32_MCx_CTL2(i), val);
 
@@ -207,11 +221,26 @@ static void cmci_discover(int banks)
                 if (val & MCI_CTL2_CMCI_EN) {
                         set_bit(i, owned);
                         __clear_bit(i, __get_cpu_var(mce_poll_banks));
+                        /*
+                         * We are able to set thresholds for some banks that
+                         * had a threshold of 0. This means the BIOS has not
+                         * set the thresholds properly or does not work with
+                         * this boot option. Note down now and report later.
+                         */
+                        if (mce_bios_cmci_threshold && bios_zero_thresh &&
+                                        (val & MCI_CTL2_CMCI_THRESHOLD_MASK))
+                                bios_wrong_thresh = 1;
                 } else {
                         WARN_ON(!test_bit(i, __get_cpu_var(mce_poll_banks)));
                 }
         }
         raw_spin_unlock_irqrestore(&cmci_discover_lock, flags);
+        if (mce_bios_cmci_threshold && bios_wrong_thresh) {
+                pr_info_once(
+                        "bios_cmci_threshold: Some banks do not have valid thresholds set\n");
+                pr_info_once(
+                        "bios_cmci_threshold: Make sure your BIOS supports this boot option\n");
+        }
 }
 
 /*
@@ -249,7 +278,7 @@ void cmci_clear(void)
                         continue;
                 /* Disable CMCI */
                 rdmsrl(MSR_IA32_MCx_CTL2(i), val);
-                val &= ~(MCI_CTL2_CMCI_EN|MCI_CTL2_CMCI_THRESHOLD_MASK);
+                val &= ~MCI_CTL2_CMCI_EN;
                 wrmsrl(MSR_IA32_MCx_CTL2(i), val);
                 __clear_bit(i, __get_cpu_var(mce_banks_owned));
         }