[Qemu-devel] Re: [PATCH 3/3] Add svm cpuid features

[Alexander Graf]

Roedel, Joerg wrote:
> On Thu, Sep 16, 2010 at 10:17:09AM -0400, Alexander Graf wrote:
>   
>> Roedel, Joerg wrote:
>>     
>>> On Thu, Sep 16, 2010 at 10:06:48AM -0400, Avi Kivity wrote:
>>>   
>>>       
>>>>   On 09/14/2010 05:52 PM, Joerg Roedel wrote:
>>>>     
>>>>         
>>>>> This patch adds the svm cpuid feature flags to the qemu
>>>>> intialization path. It also adds the svm features available
>>>>> on phenom to its cpu-definition and extends the host cpu
>>>>> type to support all svm features KVM can provide.
>>>>>
>>>>>
>>>>>       
>>>>>           
>>>> Does phenom really have vmcbclean?  I thought it was a really new feature.
>>>>     
>>>>         
>>> No, but we could emulate it on almost all hardware that has SVM. Its
>>> basically the same as with x2apic.
>>>   
>>>       
>> -cpu <non-host> is not about what we could emulate, but what the
>> hardware really is. Features not supported by the particular CPU do not
>> belong there.
>>     
>
> I'll remove it then. It would have been nice to have it there because it
> will improve performance of svm emulation. But if it is about emulating
> the real cpu then I'll just drop it.
>   

speed == -cpu host :). If the performance increase is significant, we
can always add a new cpu type for a cpu that does support those flags so
people can use it there and still be migration safe. In fact, that would
even benefit you guys as you'd sell more new machines for speed ;).


Alex