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>

diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt
index c54b4f5..de38429 100644 (file)
--- 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 ccaf7c5..54d73b1 100644 (file)
--- 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 c311122..29e87d3 100644 (file)
--- 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 098386f..5f88abf 100644 (file)
--- 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));
        }