Hi,Jiri Thanks for replying. So why VM identified different features from host is due to the hypervisor filtering. I will dig into the hypervisor of how it filter features, and update status later. Thanks again. On 2013-07-23 19:27, Jiri Denemark wrote: > On Tue, Jul 23, 2013 at 10:44:48 +0800, Peter Huang(Peng) wrote: >>> libvirt's "host-passthrough" uses "-cpu host', and it "-cpu host" >>> enables every feature that can be enabled on the host. >> From my test results, I found that even when use host-passthrough mode, VM's >> cpu features are very different from host, this doesn't match what host-passthrough >> mode's explanation. >> >> libvirt's option exlanation: >> With this mode, the CPU visible to the guest should be exactly the same as the host >> CPU even in the aspects that libvirt does not understand. > The libvirt documentation is what needs to be updated. While > host-passthrough is asking for a CPU which is as close as possible to > the real host CPU, there are features that need special handling before > they can be provided to a guest. And if the hypervisor does not provide > that handling, it may just filter such feature out. Also if some > features can be efficiently provided to a guest even though the host CPU > does not provide them (x2apic is an example of such feature), they may > be provided to a guest. > > Jirka > -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list