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Subject[PATCH -tip 1/3] x86, mce: Add mce_threshold option for intel cmci
This patch adds a kernel parameter "mce_threshold=n" to enable us
to change the default threshold for CMCI(Corrected Machine Check
Interrupt) that recent Intel processor supports.

And it also supports CMCI disabling by setting mce_threshold=0.
It would be useful if your hardware does something wrong and/or
if polling by timer is preferred than the threshold interrupt.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
---
Documentation/kernel-parameters.txt | 5 +++
arch/x86/include/asm/msr-index.h | 1 +
arch/x86/kernel/cpu/mcheck/mce_intel_64.c | 56 +++++++++++++++++++++++++++--
3 files changed, 59 insertions(+), 3 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1d8af36..7a0d117 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1267,6 +1267,11 @@ and is between 256 and 4096 characters. It is defined in the file

mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt

+ mce_threshold= [X86-64,intel] Default CMCI threshold
+ Should be unsigned integer. Setting 0 disables cmci.
+ Format: <integer>
+ Default: 1
+
md= [HW] RAID subsystems devices and level
See Documentation/md.txt.

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 2dbd231..b2b6329 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -81,6 +81,7 @@
#define MSR_IA32_MC0_CTL2 0x00000280
#define CMCI_EN (1ULL << 30)
#define CMCI_THRESHOLD_MASK 0xffffULL
+#define CMCI_THRESHOLD_VAL_MASK 0x7fffULL

#define MSR_P6_PERFCTR0 0x000000c1
#define MSR_P6_PERFCTR1 0x000000c2
diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel_64.c b/arch/x86/kernel/cpu/mcheck/mce_intel_64.c
index d6b72df..8bd5d0c 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel_64.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel_64.c
@@ -103,8 +103,6 @@ static DEFINE_PER_CPU(mce_banks_t, mce_banks_owned);
*/
static DEFINE_SPINLOCK(cmci_discover_lock);

-#define CMCI_THRESHOLD 1
-
static int cmci_supported(int *banks)
{
u64 cap;
@@ -135,6 +133,51 @@ static void intel_threshold_interrupt(void)
mce_notify_user();
}

+/*
+ * Default threshold, setting 0 disables cmci
+ */
+static unsigned long threshold_limit = 1;
+
+static int __init mcheck_threshold(char *str)
+{
+ int val;
+
+ get_option(&str, &val);
+ if (val < 0) {
+ printk(KERN_INFO "mce_threshold argument ignored.\n");
+ return 0;
+ }
+ threshold_limit = val;
+
+ return 1;
+}
+__setup("mce_threshold=", mcheck_threshold);
+
+void static cmci_set_threshold(int bank)
+{
+ u64 val, limit, max, new;
+
+ rdmsrl(MSR_IA32_MC0_CTL2 + bank, val);
+ limit = val & CMCI_THRESHOLD_VAL_MASK;
+
+ /* Thresholding available? */
+ if (!limit)
+ return;
+ /* Return if no need to change */
+ if (limit == threshold_limit)
+ return;
+
+ /* Find the maximum threshold value */
+ max = (val & ~CMCI_THRESHOLD_MASK) | CMCI_THRESHOLD_VAL_MASK;
+ wrmsrl(MSR_IA32_MC0_CTL2 + bank, max);
+ rdmsrl(MSR_IA32_MC0_CTL2 + bank, max);
+ max &= CMCI_THRESHOLD_VAL_MASK;
+ max = (threshold_limit > max ? max : threshold_limit);
+
+ new = (val & ~CMCI_THRESHOLD_MASK) | max;
+ wrmsrl(MSR_IA32_MC0_CTL2 + bank, new);
+}
+
static void print_update(char *type, int *hdr, int num)
{
if (*hdr == 0)
@@ -143,6 +186,9 @@ static void print_update(char *type, int *hdr, int num)
printk(KERN_CONT " %s:%d", type, num);
}

+/* Used to determine whether thresholding is available or not */
+#define CMCI_THRESHOLD_FIRST 1
+
/*
* Enable CMCI (Corrected Machine Check Interrupt) for available MCE banks
* on this CPU. Use the algorithm recommended in the SDM to discover shared
@@ -154,6 +200,9 @@ static void cmci_discover(int banks, int boot)
int hdr = 0;
int i;

+ if (!threshold_limit)
+ return;
+
spin_lock(&cmci_discover_lock);
for (i = 0; i < banks; i++) {
u64 val;
@@ -171,7 +220,7 @@ static void cmci_discover(int banks, int boot)
continue;
}

- val |= CMCI_EN | CMCI_THRESHOLD;
+ val |= CMCI_EN | CMCI_THRESHOLD_FIRST;
wrmsrl(MSR_IA32_MC0_CTL2 + i, val);
rdmsrl(MSR_IA32_MC0_CTL2 + i, val);

@@ -180,6 +229,7 @@ static void cmci_discover(int banks, int boot)
if (!test_and_set_bit(i, owned) || boot)
print_update("CMCI", &hdr, i);
__clear_bit(i, __get_cpu_var(mce_poll_banks));
+ cmci_set_threshold(i);
} else {
WARN_ON(!test_bit(i, __get_cpu_var(mce_poll_banks)));
}
--
1.6.2.1



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