On 31/07/2017 14:27, David Hildenbrand wrote: >> I'm not sure whether the operation of get the vcpu's priority-level is >> expensive on all architectures, so I record it in kvm_sched_out() for >> minimal the extra cycles cost in kvm_vcpu_on_spin(). >> > as you only care for x86 right now either way, you can directly optimize > here for the good (here: x86) case (keeping changes and therefore > possible bugs minimal). I agree with Cornelia that this is inconsistent, so you shouldn't update me->in_kernmode in kvm_vcpu_on_spin. However, get_cpl requires vcpu_load on Intel x86, so Mike's patch is necessary (vmx_get_cpl -> vmx_read_guest_seg_ar -> vmcs_read32). Alternatively, we can add a new callback kvm_x86_ops->sched_out to x86 KVM, and call vmx_get_cpl from the Intel implementation (vmx_sched_out). This will cache the result until the next sched_in, so that kvm_vcpu_on_spin can use it. Paolo
