[PATCH 08/35] KVM: x86: Harden against cpufreq

Avi Kivity
2009-11-19T13:35:07Z

From: Zachary Amsden <zamsden@redhat.com>

If cpufreq can't determine the CPU khz, or cpufreq is not compiled in,
we should fallback to the measured TSC khz.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
arch/x86/kvm/x86.c | 16 ++++++++++++----
1 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 098e7f8..3cffa2c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1348,8 +1348,12 @@ out:
void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
{
kvm_x86_ops->vcpu_load(vcpu, cpu);
- if (unlikely(per_cpu(cpu_tsc_khz, cpu) == 0))
- per_cpu(cpu_tsc_khz, cpu) = cpufreq_quick_get(cpu);
+ if (unlikely(per_cpu(cpu_tsc_khz, cpu) == 0)) {
+ unsigned long khz = cpufreq_quick_get(cpu);
+ if (!khz)
+ khz = tsc_khz;
+ per_cpu(cpu_tsc_khz, cpu) = khz;
+ }
kvm_request_guest_time_update(vcpu);
}

@@ -3144,8 +3148,12 @@ static void kvm_timer_init(void)
if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
cpufreq_register_notifier(&kvmclock_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
- for_each_online_cpu(cpu)
- per_cpu(cpu_tsc_khz, cpu) = cpufreq_get(cpu);
+ for_each_online_cpu(cpu) {
+ unsigned long khz = cpufreq_get(cpu);
+ if (!khz)
+ khz = tsc_khz;
+ per_cpu(cpu_tsc_khz, cpu) = khz;
+ }
} else {
for_each_possible_cpu(cpu)
per_cpu(cpu_tsc_khz, cpu) = tsc_khz;
--
1.6.5.2