x86: fix boot-time watchdog test.

Since the perf counter that the LAPIC NMI watchdog uses only
runs while the core isn't halted, and all APs are idle at
this point in the boot process, it's possible that remote
CPUs won't see any NMIs during the 10-tick waiting period.
Force all CPUs to busy-wait so we know the timers are running.

Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>

diff --git a/xen/arch/x86/nmi.c b/xen/arch/x86/nmi.c
index 6730f29a0ab0700c73f375b2fe339c3db7b15c5c..2fd864e8683be6956a7543fc397d8819a98671da 100644 (file)
--- a/xen/arch/x86/nmi.c
+++ b/xen/arch/x86/nmi.c
@@ -95,6 +95,11 @@ int nmi_active;
     (P4_CCCR_OVF_PMI0|P4_CCCR_THRESHOLD(15)|P4_CCCR_COMPLEMENT| \
      P4_CCCR_COMPARE|P4_CCCR_REQUIRED|P4_CCCR_ESCR_SELECT(4)|P4_CCCR_ENABLE)
 
+static void __init wait_for_nmis(void *p)
+{
+    mdelay((10*1000)/nmi_hz); /* wait 10 ticks */
+}
+
 int __init check_nmi_watchdog (void)
 {
     static unsigned int __initdata prev_nmi_count[NR_CPUS];
@@ -108,7 +113,12 @@ int __init check_nmi_watchdog (void)
     for_each_online_cpu ( cpu )
         prev_nmi_count[cpu] = nmi_count(cpu);
     local_irq_enable();
-    mdelay((10*1000)/nmi_hz); /* wait 10 ticks */
+
+    /* Wait for 10 ticks.  Busy-wait on all CPUs: the LAPIC counter that
+     * the NMI watchdog uses only runs while the core's not halted */
+    if ( nmi_watchdog == NMI_LOCAL_APIC )
+        smp_call_function(wait_for_nmis, NULL, 0);
+    wait_for_nmis(NULL);
 
     for_each_online_cpu ( cpu )
     {