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[Qemu-devel] [Solved]FYI//Re: [Question] why x2apic's set by default wit

From: Peter Huang(Peng)
Subject: [Qemu-devel] [Solved]FYI//Re: [Question] why x2apic's set by default without host support(on Nehalem CPU).
Date: Wed, 24 Jul 2013 10:54:57 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; rv:11.0) Gecko/20120327 Thunderbird/11.0.1

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:

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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