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



"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.

That said, why is mac99 the default?  It doesn't seem to work at all for
me.  Even with TCG, I've had more luck with -M pseries.

While adding an accelerator specific default, if mac99 is the wrong
default for TCG, then we should change it.

Regards,

Anthony Liguori

>
>
> Daniel
> -- 
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