[Xen-devel] [PATCH v1] xen/mce: Don't spam the console with "CPUx: Temperature z" (v2)

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

If the machine has been quite busy it ends up with these
messages printed on the hypervisor console:

(XEN) CPU3: Temperature/speed normal
(XEN) CPU1: Temperature/speed normal
(XEN) CPU0: Temperature/speed normal
(XEN) CPU1: Temperature/speed normal
(XEN) CPU0: Temperature/speed normal
(XEN) CPU2: Temperature/speed normal
(XEN) CPU3: Temperature/speed normal
(XEN) CPU0: Temperature/speed normal
(XEN) CPU2: Temperature/speed normal
(XEN) CPU3: Temperature/speed normal
(XEN) CPU1: Temperature/speed normal
(XEN) CPU0: Temperature above threshold
(XEN) CPU0: Running in modulated clock mode
(XEN) CPU1: Temperature/speed normal
(XEN) CPU2: Temperature/speed normal
(XEN) CPU3: Temperature/speed normal

While the state changes are important, the non-altered
state information is not needed. As such add a latch
mechanism to only print the information if it has
changed since the last update.

This was observed on Intel DQ67SW,
BIOS SWQ6710H.86A.0066.2012.1105.1504 11/05/2012

CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
[v2: Redo per Daniel and Boris's review]
---
 xen/arch/x86/cpu/mcheck/mce_intel.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/cpu/mcheck/mce_intel.c 
b/xen/arch/x86/cpu/mcheck/mce_intel.c
index b32fdb2..a5caf47 100644
--- a/xen/arch/x86/cpu/mcheck/mce_intel.c
+++ b/xen/arch/x86/cpu/mcheck/mce_intel.c
@@ -49,11 +49,13 @@ static int __read_mostly nr_intel_ext_msrs;
 #define INTEL_SRAR_INSTR_FETCH 0x150
 
 #ifdef CONFIG_X86_MCE_THERMAL
+#define MCE_RING                0x1
 static void intel_thermal_interrupt(struct cpu_user_regs *regs)
 {
     uint64_t msr_content;
     unsigned int cpu = smp_processor_id();
     static DEFINE_PER_CPU(s_time_t, next);
+    static DEFINE_PER_CPU(int, last_state) = -1;
 
     ack_APIC_irq();
 
@@ -62,10 +64,13 @@ static void intel_thermal_interrupt(struct cpu_user_regs 
*regs)
 
     per_cpu(next, cpu) = NOW() + MILLISECS(5000);
     rdmsrl(MSR_IA32_THERM_STATUS, msr_content);
-    if (msr_content & 0x1) {
+    if ( __get_cpu_var(last_state) == (msr_content & MCE_RING) )
+        return;
+    per_cpu(last_state, cpu) = msr_content & MCE_RING;
+    if ( msr_content & MCE_RING )
+    {
         printk(KERN_EMERG "CPU%d: Temperature above threshold\n", cpu);
-        printk(KERN_EMERG "CPU%d: Running in modulated clock mode\n",
-                cpu);
+        printk(KERN_EMERG "CPU%d: Running in modulated clock mode\n", cpu);
         add_taint(TAINT_MACHINE_CHECK);
     } else {
         printk(KERN_INFO "CPU%d: Temperature/speed normal\n", cpu);
-- 
1.9.3


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