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

[Thomas Huth]

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