Under pHyp, recent kernels use the dispatch trace log (DTL) to measure stolen time. The DTL is a ring buffer containing 48-byte entries, where the hypervisor creates an entry each time a virtual cpu is dispatched. The entries contain a couple of fields that the kernel interprets as stolen time, measured in timebase ticks. Although this is not an ideal interface, it is one that our guest kernels already support. So this series of patches adds code to Book3S HV KVM to measure stolen time and report it to the guest via a dispatch trace log. Stolen time is measured per virtual core (set of 4 vcpus, on POWER7) as being all the time when no vcpu thread is executing inside kvmppc_run_core(), or when a vcpu thread is running the virtual core but is preempted. The first patch fixes some potential races with the registration and unregistration of the DTL and the other per-virtual-processor areas, since the guest can (un)register a per-virtual-processor area for one vcpu in a call to the H_REGISTER_VPA hypercall on another vcpu, and hence potentially while KVM is using a previously-registered area. The second patch adds the machinery for measuring stolen time and for creating DTL entries. Paul. -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
