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

[luigi burdo]

hi just for gave a complete infos about this point.
this is x64 threadripper with mac99 emulation in qemu vs qemu kvm on 970Mp 2.5 
ghz (mac quad) 
https://scontent.fnap1-1.fna.fbcdn.net/v/t1.0-9/27540591_10211001296249952_3934778983080779619_n.jpg?_nc_cat=0&oh=523c1f6cddb62032b5879224613d210d&oe=5BBE5122

the qemu kvm is really slow compared mac-on-linux kvm, same is for sheepshaver.
on same benchmark speed is near 75 points on cpu on MOL and 95 (near the host 
cpu) on sheepshaver. 
fpu performances is really low about 90% slower than the host on qemu in kvm.

luigi

Inviato da iPad

> Il giorno 21 giu 2018, alle ore 03:10, Programmingkid <address@hidden> ha 
> scritto:
> 
> 
>> 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.