Re: [Qemu-ppc] PowerPC, enable-kvm, and the Power processor

[Programmingkid]

> On Jun 20, 2018, at 9:06 PM, Thomas Huth <address@hidden> wrote:
> 
> On 20.06.2018 22:04, Programmingkid wrote:
>> 
>>> On Jun 20, 2018, at 2:01 PM, Howard Spoelstra <address@hidden> wrote:
>>> 
>>> Hi,
>>> 
>>> I have qemu-system-ppc running with kvm support in Linux on a Mac Mini
>>> G4 1,5Ghz.
>>> I had to compile kvm support into a new kernel.
>>> 
>>> Best,
>>> Howard
>>> 
>>> On Wed, Jun 20, 2018 at 7:58 PM, Programmingkid
>>> <address@hidden> wrote:
>>>> 
>>>>> On Jun 20, 2018, at 1:53 PM, Thomas Huth <address@hidden> wrote:
>>>>> 
>>>>> On 20.06.2018 18:19, Programmingkid wrote:
>>>>>> Would anyone know if qemu-system-ppc could be run on an IBM Power 
>>>>>> processor in kvm mode? I am interested in finding any bugs with the 
>>>>>> emulated PowerPC processors in QEMU. My theory is if QEMU runs 
>>>>>> differently in KVM mode than pure emulation mode, we might have an 
>>>>>> emulation issue.
>>>>> 
>>>>> You mean the 32-bit only qemu-system-ppc? Or do you mean
>>>>> qemu-system-ppc64, too? It definitely runs on the latter, and I think it
>>>>> also used to work with the 32-bit only binary in former times (using
>>>>> kvm-pr) ... but it could be that the 32-bit version is not tested very
>>>>> well anymore, so no clue about the current shape...
>>>>> 
>>>>> Thomas
>>>> 
>>>> Thanks for the info. I was referring to testing a 32-bit version of the 
>>>> PowerPC processor like the PowerPC 750 (G3) with qemu-system-ppc.
>> 
>> Hi Howard. I just finished doing a test on my 2.0 Ghz iMac G5 with a Mac OS 
>> 10.4 guest. KVM mode does work for me also but it is slow. I always thought 
>> that using QEMU in KVM mode would make it run the guest at near native 
>> speed. I saw nothing even close to that kind of speed.
> 
> That's likely because you run with KVM-PR on the G5, i.e. a
> trap-n-emulate implementation of KVM. Only user mode instructions are
> run natively, while privileged instructions (kernel mode) are emulated.
> See
> https://wiki.qemu.org/Documentation/Platforms/POWER#Switching_between_the_KVM-PR_and_KVM-HV_kernel_module
> for some details.
> 
> Thomas

That makes sense. The Intel processors have VT-x instructions that make 
virtualization much faster. Thank you.