FYI, just for information sharing.

KVM emulated x2apic feature no matter host supports it or not.
You can get the code from arch/x86/kvm/cpuid.c.
kvm_dev_ioctl_get_supported_cpuid ()->do_cpuid_ent()

  /* we support x2apic emulation even if host does not support

                 * it since we emulate x2apic in software */

                entry->ecx |= F(*X2APIC*);


QEMU will get this feature through kvm_ioctl().

On 2013-07-24 8:48, Peter Huang(Peng) wrote:
> 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.