Re: [Qemu-devel] [qemu-devel][libvirt] Default machine type setting for ppc64

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 21/05/13 14:04, Anthony Liguori wrote:
> "Daniel P. Berrange" <berrange@redhat.com> writes:
> 
>> On Tue, May 21, 2013 at 07:55:27PM +1000, Paul Mackerras wrote:
>>> On Tue, May 21, 2013 at 09:39:53AM +0100, Daniel P. Berrange wrote:
>>>> QEMU has the notion of a default machine for each target, and that is
>>>> what libvirt uses if the user hasn't specified a machine.  It is not
>>>> libvirt's job to override QEMU's notion of the default machine here,
>>>> so if the 'mac99' machine type isn't suitable as the default either
>>>> QEMU needs to change that for the ppc target, or the user needs to
>>>> explicitly specify their desired machine type.
>>>
>>> We are getting the default changed to 'pseries', at least for cases
>>> where pseries support is compiled in, which isn't necessarily
>>> always.  That will of course not satisfy the Freescale guys.
>>>
>>> I think libvirt needs some more sensible way to ask qemu what its
>>> capabilities are.  Currently it has no way to ask qemu "what machines
>>> can you emulate with kvm acceleration?"  If the user has asked for a
>>> KVM domain then the default machine should be one that can be provided
>>> by KVM.  At present it isn't, on PowerPC.
>>
>> If QEMU can provide more intelligent info in this respect, then
>> libvirt can use it. We're doing the best we can with picking
>> defaults given the info QEMU currently provides us.
> 
> We've talked in the past about having an accelerator specific machine
> default.  I think this is a perfectly reasonable thing to do and would
> solve the problem for ARM and for PPC.

If we get such thing, then virtio-ccw might also be the right default for kvm 
on s390.

Christian