Re: [Qemu-devel] [PATCH 2/2] qemu-kvm: Add svm cpuid features

Avi Kivity
2010-09-12T08:01:41Z

On 09/12/2010 09:16 AM, Alexander Graf wrote:
>>>
>>> Depends on which Phenom you have. A Phenom II has NRIPSAVE but the old
>>> Phenoms don't have it. For the SVM features it is not that important
>>> what the host hardware supports but what KVM can emulate. VMCBCLEAN can
>>> be emulated without supporting it in the host for example.
>> Well, let's have a phenom2 type for those new features (and any other features the phenom 2 has). What's the point of using the name of existing hardware if it doesn't match that hardware?
> Isn't that what cpu=host is there for? I don't want to see cpu type cluttering like we have it on ppc. I added the core2duo type for Mac OS X guests for which those are basically the oldest supported CPUs.

-cpu host is to all supported features into your guest.
-cpu phenom is to pretend you are running on a phenom cpu. This is
useful for a migration farm for which the greatest common denominator is
a phenom.

Those are separate use cases.

> For the Phenom type, I honestly don't remember why, but there was also a good reason to add it. In fact, I use it today to have nested virt without -cpu host on hardware that's too new for my guests.

Curious, what guests balk at modern hardware but are fine with phenom?

> Either way, I don't think we need a phenom2 type. The features additional are minor enough to not really matter and all use cases I can come up with require either -cpu host (local virt) or -cpu phenom (migration).

I'm fine with this (or with adding phenom2). But don't make phenom
contain flags that real phenoms don't have.

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