Re: [Qemu-devel] [PATCH v3 1/2] QMP: add query-hotpluggable-cpus

[David Gibson <dgibson@redhat.com>]

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On Mon, 21 Mar 2016 11:53:23 +0100
Igor Mammedov <imammedo@redhat.com> wrote:

> On Fri, 18 Mar 2016 16:26:28 -0300
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
> > On Tue, Mar 15, 2016 at 02:24:07PM +0100, Igor Mammedov wrote:
> > [...]  
> > > diff --git a/stubs/qmp_query_hotpluggable_cpus.c b/stubs/qmp_query_hotpluggable_cpus.c
> > > new file mode 100644
> > > index 0000000..21a75a3
> > > --- /dev/null
> > > +++ b/stubs/qmp_query_hotpluggable_cpus.c
> > > @@ -0,0 +1,9 @@
> > > +#include "qemu/osdep.h"
> > > +#include "qapi/qmp/qerror.h"
> > > +#include "qmp-commands.h"
> > > +
> > > +HotpluggableCPUList *qmp_query_hotpluggable_cpus(Error **errp)
> > > +{
> > > +    error_setg(errp, QERR_FEATURE_DISABLED, "query-hotpluggable-cpus");
> > > +    return NULL;
> > > +}    
> > 
> > Sorry if this was discussed in previous threads that I haven't
> > read, but: isn't this supposed to be a MachineClass method?  I
> > remember David saying once that we have the habit of assuming
> > that a single QEMU binary can run only one family of machines
> > that are very similar (like x86), but that's not always true.  
> Stub approach works for current qemu with one target per binary
> but it won't for multi-target binary.

This approach won't work even now.  We have draft implementations of
the hook for spapr, but those are absolutely wrong for mac99 or the
many other ppc machine classes.

> I've been trying to not clutter MachineClass with hooks
> that not must have right now but I don't have a strong opinion
> on this so if MachineClass method is preferred way,
> I can rewrite it this patch to use it on respin.
> 
> 


-- 
David Gibson <dgibson@redhat.com>
Senior Software Engineer, Virtualization, Red Hat

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