Re: [PATCH 00/18] KVM: PPC: Virtualize Gekko guests

[Avi Kivity <avi@redhat.com>]

On 02/07/2010 05:49 PM, Alexander Graf wrote:
> Am 07.02.2010 um 13:54 schrieb Avi Kivity <avi@redhat.com>:
>
>> On 02/04/2010 05:55 PM, Alexander Graf wrote:
>>> In an effort to get KVM on PPC more useful for other userspace users 
>>> than
>>> Qemu, I figured it'd be a nice idea to implement virtualization of the
>>> Gekko CPU.
>>>
>>> The Gekko is the CPU used in the GameCube. In a slightly more modern
>>> fashion it lives on in the Wii today.
>>>
>>> Using this patch set and a modified version of Dolphin, I was able to
>>> virtualize simple GameCube demos on a 970MP system.
>>>
>>> As always, while getting this to run I stumbled across several broken
>>> parts and fixed them as they came up. So expect some bug fixes in this
>>> patch set too.
>>>
>>
>> This is halfway into emulation rather than virtualization.  What does 
>> performance look like when running fpu intensive applications?
>
> It is for the FPU. It is not for whatever runs on the CPU.
>
> I haven't benchmarked things so far,
>
> The only two choices I have to get this running is in-kernel emulation 
> or userspace emulation. According to how x86 deals with things I 
> suppose full state transition to userspace and continuing emulation 
> there isn't considered a good idea. So I went with in-kernel.

It's not a good idea for the kernel either, if it happens all the time.  
If a typical Gekko application uses the fpu and the emulated 
instructions intensively, performance will suck badly (as in: qemu/tcg 
will be faster).

-- 
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