2017-12-01 13:30-0600, Natarajan, Janakarajan: > On 11/17/2017 5:44 AM, Borislav Petkov wrote: > > On Thu, Nov 16, 2017 at 12:00:11PM -0600, Natarajan, Janakarajan wrote: > > > Ah my apologies. So when the pmu is initialized the cpuid entries > > > aren't available then. > > So let's see: > > > > ... kvm_arch_vcpu_create() -> > > svm_create_vcpu() -> > > kvm_vcpu_init() -> > > kvm_arch_vcpu_init() -> > > > > <--- HERE > > > > kvm_pmu_init() > > > > But at HERE in kvm_arch_vcpu_init() right before kvm_pmu_init() we do already query > > cpuid: > > > > vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu); > > > > so it's not like we don't know about cpuid leafs at that point. Which > > would mean that the code can be made to set the CPU family earlier, > > before kvm_pmu_init() runs so that you have the proper CPU family and > > thus have this thing properly designed. > > > > Maybe Paolo and Radim have a better suggestion here... > > Paolo, Radim any suggestions about this. I feel that the number of counters > initialized can be 6 This is the best solution with the current framework. > and the subsequent code (kvm_pmu_refresh()) takes care of the number of > counters to be used (4 or 6) > based on the vcpu family. Can't we look only at X86_FEATURE_PERFCTR_CORE and completely ignore the AMD family? Using the family would bring problems with compatiblity. Thanks.
