Re: [kvm-devel] [Qemu-devel] expose host CPU features to guests: Take 3

[Avi Kivity]

Avi Kivity wrote:
>>>     
>>>       
>> I've got a remark about this: why this has to be added to the Qemu
>> code ?
>> Imho, all is needed is an implementation of the -cpu option for
>> x86/x86_64 target. Then, an external tool (even a shell script) can be
>> used to determine what is the host CPU if you want to select the exact
>> same CPU to be emulated in Qemu. It seems to me that trying to do so is
>> out of the scope of Qemu code and just add unneeded complexity.
>>   
>>     
>
> Indeed for regular qemu this is useless.  But it is useful for kqemu
> (for which there is support in mainline qemu), and for kvm (which we
> hope to merge one day).
>
>   

Actually (as Izik Eidus reminds me), this isn't very useful for kqemu as
it can't trap cpuid in all circumstances.

So this is mainly useful for kvm.  I hope it will be applied regardless
of that, as there is agreement that kvm support should be merged.  I'd
much rather pull the feature from qemu rather than carry it as an
additional patch.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to 
panic.