Re: [Qemu-devel] Current differences between qemu --enable-kvm and qemu-kvm?

[Erik Rull <erik.rull@rdsoftware.de>]

Jan Kiszka wrote:
> On 2012-05-22 07:34, Jan Kiszka wrote:
>> On 2012-05-22 07:04, Stefan Hajnoczi wrote:
>>> On Mon, May 21, 2012 at 5:54 PM, Erik Rull<webmaster@rdsoftware.de>  wrote:
>>>> is there a summary existing that shows up the rough or actual differences
>>>> between qemu --enable-kvm and qemu-kvm? I tested both versions with the same
>>>> compile and start options, the CPU performance results are identical, only
>>>> the bootup time of my guest system with qemu-kvm seemed to be a bit faster
>>>> (not measured, it just feeled so).
>>
>> Current upstream does not enable the in-kernel irqchip of KVM by
>> default. This should explain the difference in boot-up times. Try
>> "-machine accel=kvm,kernel_irqchip=on". But the default will be on, just
>> like in qemu-kvm, once [1] is merged.
>>
>>>
>>> For production KVM instances I think it still makes sense to use
>>> qemu-kvm packages from your distro or qemu-kvm upstream source.
>>>
>>> Jan Kiszka has reduced the delta between qemu.git and qemu-kvm.git to
>>> the point where I think the list of differences is rather small -
>>> maybe PCI passthrough stuff, irqfd for vhost-net (which is now also
>>> being upstreamed into qemu.git), and a few other things I don't know
>>> of.
>>
>> Right, the list of differences is dramatically shrinking. As stated in
>> [2], soon only PCI passthrough and legacy interface dependencies on
>> qemu-kvm will be the remaining reasons to use it. If we are lucky, PCI
>> passthrough will also make it into upstream for QEMU 1.2, we are working
>> on this.
>>
>>>
>>> For development most patches should be against qemu.git unless they
>>> have a dependency on qemu-kvm.git code.
>>
>> Yes, unless you are working on the upstream merge itself, there is
>> practically no reason anymore to develop against qemu-kvm directly.
>>
>> Jan
>>
>> [1] http://thread.gmane.org/gmane.comp.emulators.kvm.devel/91171
>> [2] http://thread.gmane.org/gmane.comp.emulators.kvm.devel/91026
>>
>
> I've added some more details on this to the QEMU wiki, see
> http://wiki.qemu.org/KVM.
>
> BTW, if someone could have a look at the VGA diffs and resolve them,
> that would be great. Gerd, what's the state of switching the BIOS?
>
> Jan
>

Hi all,

thanks a lot!

I don't use PCI device assignment - so the missing irqchip-default-option 
should be the biggest difference between these two versions, right?

Best regards,

Erik