Paolo Bonzini <pbonz...@redhat.com> writes: > On 26/11/18 14:59, Vitaly Kuznetsov wrote: >> It was found that QMP users of QEMU (e.g. libvirt) may need >> HV_CPUID_ENLIGHTMENT_INFO.EAX/HV_CPUID_NESTED_FEATURES.EAX information. In >> particular, 'hv_tlbflush' and 'hv_evmcs' enlightenments are only exposed in >> HV_CPUID_ENLIGHTMENT_INFO.EAX. >> >> HV_CPUID_NESTED_FEATURES.EAX is exposed for two reasons: convenience >> (we don't need to export it from hyperv_handle_properties() and as >> future-proof for Enlightened MSR-Bitmap, PV EPT invalidation and >> direct virtual flush features. >> >> Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com> > > Can you add a comment to feature_word_info, explaining why the > feat_names are not set?
I had to do some code archeology to make sure I understand, I think it goes back to http://lists.gnu.org/archive/html/qemu-devel/2016-06/msg06579.html So the comment (probably added before FEAT_HYPERV_EAX definition) would be ".feat_names are commented out for Hyper-V enlightenments because we don't want to have two different ways for enabling them on QEMU command line. Some features (e.g. "hyperv_time", "hyperv_vapic", ...) require enabling several feature bits simultaneously, exposing these bits individually may just confuse guests." Would do? -- Vitaly
