[libvirt] [Solved]FYI//Re: [Qemu-devel] [Question] why x2apic's set by default without host support(on Nehalem CPU).

[Peter Huang(Peng)]

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.
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