Commit 6b7d7e76 authored by Zachary Amsden's avatar Zachary Amsden Committed by Avi Kivity
Browse files

KVM: x86: Harden against cpufreq 



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: default avatarZachary Amsden <zamsden@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 565d0998

arch/x86/kvm/x86.c

+12 −4
Original line number Diff line number Diff line
@@ -1348,8 +1348,12 @@ long kvm_arch_dev_ioctl(struct file *filp, 
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;