[PATCH RFC: kvm tsc virtualization 11/20] Use highest TSC frequency as reference clock

Zachary Amsden
2009-12-15T04:09:48Z

If CPU frequency governors can change the TSC frequency, use
the highest possible frequency as the reference.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
---
arch/x86/kvm/x86.c | 9 ++++++++-
1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 520ea6a..3c4266f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3701,7 +3701,15 @@ static void kvm_timer_init(void)
* can change at any time.
*/
register_cpu_notifier(&kvm_x86_cpu_notifier);
+ ref_tsc_khz = tsc_khz;
if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
+#ifdef CONFIG_CPU_FREQ
+ struct cpufreq_policy policy;
+
+ cpufreq_get_policy(&policy, get_cpu());
+ ref_tsc_khz = policy.cpuinfo.max_freq;
+ put_cpu();
+#endif
cpufreq_register_notifier(&kvmclock_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
for_each_online_cpu(cpu) {
@@ -3718,7 +3726,6 @@ static void kvm_timer_init(void)
per_cpu(cpu_tsc_khz, cpu) = tsc_khz;
}
tsc_base_cpu = get_cpu();
- ref_tsc_khz = per_cpu(cpu_tsc_khz, tsc_base_cpu);
resync(NULL);
put_cpu();
}
--
1.6.5.2