On 21-03-19, 12:45, Peter Zijlstra wrote:
> On Wed, Mar 20, 2019 at 10:22:23AM +0530, Viresh Kumar wrote:
> > diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> > index 3fae23834069..b2fe665878f7 100644
> > --- a/arch/x86/kernel/tsc.c
> > +++ b/arch/x86/kernel/tsc.c
> > @@ -958,10 +958,15 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
> > struct cpufreq_freqs *freq = data;
> > unsigned long *lpj;
> >
> > + if (WARN_ON_ONCE(cpumask_weight(freq->policy->related_cpus) != 1)) {
> > + mark_tsc_unstable("cpufreq changes: related CPUs affected");
>
> I suspect this is a big fat nop, but it won't hurt.
>
> > + return 0;
> > + }
> > +
> > lpj = &boot_cpu_data.loops_per_jiffy;
> > #ifdef CONFIG_SMP
> > if (!(freq->flags & CPUFREQ_CONST_LOOPS))
> > - lpj = &cpu_data(freq->cpu).loops_per_jiffy;
> > + lpj = &cpu_data(freq->policy->cpu).loops_per_jiffy;
> > #endif
> >
> > if (!ref_freq) {
> > @@ -977,7 +982,7 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
> > if (!(freq->flags & CPUFREQ_CONST_LOOPS))
> > mark_tsc_unstable("cpufreq changes");
> >
> > - set_cyc2ns_scale(tsc_khz, freq->cpu, rdtsc());
> > + set_cyc2ns_scale(tsc_khz, freq->policy->cpu, rdtsc());
> > }
> >
> > return 0;
>
> Just wondering, since we say x86 cpufreq handlers will only have a
> single CPU here,
>
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 65e4559eef2f..1ac8c710cccc 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -6649,10 +6649,8 @@ static void kvm_hyperv_tsc_notifier(void)
> > }
> > #endif
> >
> > -static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
> > - void *data)
> > +static void __kvmclock_cpufreq_notifier(struct cpufreq_freqs *freq, int cpu)
> > {
> > - struct cpufreq_freqs *freq = data;
> > struct kvm *kvm;
> > struct kvm_vcpu *vcpu;
> > int i, send_ipi = 0;
> > @@ -6696,17 +6694,12 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va
> > *
> > */
> >
> > - if (val == CPUFREQ_PRECHANGE && freq->old > freq->new)
> > - return 0;
> > - if (val == CPUFREQ_POSTCHANGE && freq->old < freq->new)
> > - return 0;
> > -
> > - smp_call_function_single(freq->cpu, tsc_khz_changed, freq, 1);
> > + smp_call_function_single(cpu, tsc_khz_changed, freq, 1);
> >
> > spin_lock(&kvm_lock);
> > list_for_each_entry(kvm, &vm_list, vm_list) {
> > kvm_for_each_vcpu(i, vcpu, kvm) {
> > - if (vcpu->cpu != freq->cpu)
> > + if (vcpu->cpu != cpu)
> > continue;
> > kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
> > if (vcpu->cpu != smp_processor_id())
> > @@ -6728,8 +6721,24 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va
> > * guest context is entered kvmclock will be updated,
> > * so the guest will not see stale values.
> > */
> > - smp_call_function_single(freq->cpu, tsc_khz_changed, freq, 1);
> > + smp_call_function_single(cpu, tsc_khz_changed, freq, 1);
> > }
> > +}
> > +
> > +static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
> > + void *data)
> > +{
> > + struct cpufreq_freqs *freq = data;
> > + int cpu;
> > +
> > + if (val == CPUFREQ_PRECHANGE && freq->old > freq->new)
> > + return 0;
> > + if (val == CPUFREQ_POSTCHANGE && freq->old < freq->new)
> > + return 0;
> > +
> > + for_each_cpu(cpu, freq->policy->cpus)
> > + __kvmclock_cpufreq_notifier(freq, cpu);
> > +
> > return 0;
> > }
> >
>
> Then why to we pretend otherwise here?
My intention was to not add any bug here because of lack of my
knowledge of the architecture in question and so I tried to be safe.
If you guys think the behavior should be same here as of the tsc, then
we can add similar checks here.
--
viresh
