summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/kvmclock.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/kernel/kvmclock.c')
-rw-r--r--arch/x86/kernel/kvmclock.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index d02def06ca91..774ac4991568 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -78,6 +78,34 @@ static cycle_t kvm_clock_read(void)
return ret;
}
+/*
+ * If we don't do that, there is the possibility that the guest
+ * will calibrate under heavy load - thus, getting a lower lpj -
+ * and execute the delays themselves without load. This is wrong,
+ * because no delay loop can finish beforehand.
+ * Any heuristics is subject to fail, because ultimately, a large
+ * poll of guests can be running and trouble each other. So we preset
+ * lpj here
+ */
+static unsigned long kvm_get_tsc_khz(void)
+{
+ return preset_lpj;
+}
+
+static void kvm_get_preset_lpj(void)
+{
+ struct pvclock_vcpu_time_info *src;
+ unsigned long khz;
+ u64 lpj;
+
+ src = &per_cpu(hv_clock, 0);
+ khz = pvclock_tsc_khz(src);
+
+ lpj = ((u64)khz * 1000);
+ do_div(lpj, HZ);
+ preset_lpj = lpj;
+}
+
static struct clocksource kvm_clock = {
.name = "kvm-clock",
.read = kvm_clock_read,
@@ -153,6 +181,7 @@ void __init kvmclock_init(void)
pv_time_ops.get_wallclock = kvm_get_wallclock;
pv_time_ops.set_wallclock = kvm_set_wallclock;
pv_time_ops.sched_clock = kvm_clock_read;
+ pv_time_ops.get_tsc_khz = kvm_get_tsc_khz;
#ifdef CONFIG_X86_LOCAL_APIC
pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock;
#endif
@@ -163,6 +192,7 @@ void __init kvmclock_init(void)
#ifdef CONFIG_KEXEC
machine_ops.crash_shutdown = kvm_crash_shutdown;
#endif
+ kvm_get_preset_lpj();
clocksource_register(&kvm_clock);
}
}
OpenPOWER on IntegriCloud