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can some one please clarify this.

I am new to kvm and created two guest instances one linux and one windows.

On both Guests, CPU is showing as QEMU virtual CPU,why is it so?

if kvm utilizes hardware virtualization and Qemu an emulator then what is the role of kvm in virtualization,since in this case its showing only emulated cpu,which i believe is the work of Qemu and not kvm.

On xen, which i am familiar guests cpu are shown as it like an actual hardware,even if it is using qemu drivers.

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closed as not a real question by Tom O'Connor, RobM, mgorven, mdpc, Khaled Mar 1 '13 at 18:10

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

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3 Answers 3

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By default, QEMU/KVM exposes only a subset of CPU features to guests, so that a VM can be migrated from one CPU to another (e.g. from an Intel Xeon to an AMD Opteron) without any ill effects.

You can override this behavior if you wish, by passing parameters on the qemu command line, or setting the appropriate CPU options in your GUI/XML front end. You can select specific CPU features to expose, or to pass through all CPU features.

If you choose to override any of the parameters, then you will only be able to migrate the VM to another CPU which also has those features. If you choose to pass all host CPU features to the guest, then it will also expose the name of the CPU, and you will be unable to migrate the VM to a CPU of a different type.

The difference between QEMU and KVM is that QEMU is full processor emulation, while KVM provides full hardware virtualization (HVM) using the processor's native virtualization capability (Intel VT-x or AMD SVM) to provide near-native CPU performance. As a result, the former is much slower than the latter.

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can u please tell me what is the role of kvm in it,Isn't it emulation and what is kvm's role? –  kevin Feb 28 '13 at 8:43
    
That's definitely a different question. –  Michael Hampton Feb 28 '13 at 8:46
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i guess that is my question :) –  kevin Feb 28 '13 at 8:46
    
in xen hvm guests can be migrated,even if it shows actual cpu hardware name. –  kevin Feb 28 '13 at 8:59
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That may be your question, but it isn't the question you asked. I answered the question you asked, not the question you didn't ask. Consider clarifying your question or asking a new question - and reading the copious amounts of information about KVM available on the Internet. –  Michael Hampton Feb 28 '13 at 9:10
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What's in a name? that which we call a rose

By any other name would smell as sweet;

And so also true of virtualised CPUs.

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Definitely i am not the one who gave - to your answer :).It looks like there are people who have this doubt. –  kevin Feb 28 '13 at 8:51
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Eh. Some people are tossers. –  Tom O'Connor Feb 28 '13 at 9:07
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qemu a user space program emulates hosts hardware utilizing /dev/kvm interface.KVM itself doesnot have any capability to emulate.

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This does not answer my question fully,but got some idea. –  kevin Feb 28 '13 at 9:57
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