Zachary Amsden wrote: > They are globals, not clearly protected by any ordering or locking, and > vulnerable to various startup races. > > Instead, for variable TSC machines, register the cpufreq notifier and get > the TSC frequency directly from the cpufreq machinery. Not only is it > always right, it is also perfectly accurate, as no error prone measurement > is required. > > On such machines, when a new CPU online is brought online, it isn't clear what > frequency it will start with, and it may not correspond to the reference, thus > in hardware_enable we clear the cpu_tsc_khz variable to zero and make sure > it is set before running on a VCPU. > > Signed-off-by: Zachary Amsden <[email protected]> > --- > arch/x86/kvm/x86.c | 26 ++++++++++++++++---------- > 1 files changed, 16 insertions(+), 10 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 15d2ace..de4ce8f 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1326,6 +1326,8 @@ 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); > kvm_request_guest_time_update(vcpu); > } > > @@ -3061,9 +3063,6 @@ static void bounce_off(void *info) > /* nothing */ > } > > -static unsigned int ref_freq; > -static unsigned long tsc_khz_ref; > - > static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned > long val, > void *data) > { > @@ -3072,14 +3071,11 @@ static int kvmclock_cpufreq_notifier(struct > notifier_block *nb, unsigned long va > struct kvm_vcpu *vcpu; > int i, send_ipi = 0; > > - if (!ref_freq) > - ref_freq = freq->old; > - > if (val == CPUFREQ_PRECHANGE && freq->old > freq->new) > return 0; > if (val == CPUFREQ_POSTCHANGE && freq->old < freq->new) > return 0; > - per_cpu(cpu_tsc_khz, freq->cpu) = cpufreq_scale(tsc_khz_ref, ref_freq, > freq->new); > + per_cpu(cpu_tsc_khz, freq->cpu) = freq->new; > > spin_lock(&kvm_lock); > list_for_each_entry(kvm, &vm_list, vm_list) { > @@ -3120,12 +3116,14 @@ static void kvm_timer_init(void) > { > int cpu; > > - for_each_possible_cpu(cpu) > - per_cpu(cpu_tsc_khz, cpu) = tsc_khz; > if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) { > - tsc_khz_ref = tsc_khz; > cpufreq_register_notifier(&kvmclock_cpufreq_notifier_block, > CPUFREQ_TRANSITION_NOTIFIER); > + for_each_online_cpu(cpu) > + per_cpu(cpu_tsc_khz, cpu) = cpufreq_get(cpu);
This doesn't build for !CONFIG_CPU_FREQ. Jan
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