On Tue, Jun 03, 2014 at 05:46:11PM +0530, Aneesh Kumar K.V wrote: > We use time base for PURR and SPURR emulation with PR KVM since we > are emulating a single threaded core. When using time base > we need to make sure that we don't accumulate time spent in the host > in PURR and SPURR value. Mostly looks good except for this... > @@ -170,6 +175,11 @@ void kvmppc_copy_from_svcpu(struct kvm_vcpu *vcpu, > > out: > preempt_enable(); > + /* > + * Update purr and spurr using time base > + */ > + vcpu->arch.purr += get_tb() - vcpu->arch.entry_tb; > + vcpu->arch.spurr += get_tb() - vcpu->arch.entry_tb; You need to do those updates before the "out:" label. Otherwise if this function gets called with !svcpu->in_use (which can happen if CONFIG_PREEMPT is enabled) we would do these updates a second time for one guest exit. The thing is that kvmppc_copy_from_svcpu() can get called from kvmppc_core_vcpu_put_pr() if the vcpu task gets preempted on the way out from the guest before we get to the regular call of kvmppc_copy_from_svcpu(). It would then get called again when the task gets to run, but this time it does nothing because svcpu->in_use is false. Paul. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
