On Mon, 7 Feb 2022 09:14:37 +0100
Igor Mammedov <imammedo@xxxxxxxxxx> wrote:
> On Sat, 5 Feb 2022 13:45:24 +0100
> Philippe Mathieu-Daudé <f4bug@xxxxxxxxx> wrote:
>
> > Previously CPUs were exposed in the QOM tree at a path
> >
> > /machine/unattached/device[nn]
> >
> > where the 'nn' of the first CPU is usually zero, but can
> > vary depending on what devices were already created.
> >
> > With this change the CPUs are now at
> >
> > /machine/cpu[nn]
> >
> > where the 'nn' of the first CPU is always zero.
>
> Could you add to commit message the reason behind the change?
regardless, it looks like unwarranted movement to me
prompted by livirt accessing/expecting a QOM patch which is
not stable ABI. I'd rather get it fixed on libvirt side.
If libvirt needs for some reason access a CPU instance,
it should use @query-hotpluggable-cpus to get a list of CPUs
(which includes QOM path of already present CPUs) instead of
hard-codding some 'well-known' path as there is no any guarantee
that it will stay stable whatsoever.
> > Note: This (intentionally) breaks compatibility with current
> > libvirt code that looks for "/machine/unattached/device[0]"
> > in the assumption it is the first CPU.
> Why libvirt does this in the first place?
>
>
> > Cc: libvir-list@xxxxxxxxxx
> > Suggested-by: Daniel P. Berrangé <berrange@xxxxxxxxxx>
> > Reviewed-by: Daniel P. Berrangé <berrange@xxxxxxxxxx>
> > Signed-off-by: Philippe Mathieu-Daudé <f4bug@xxxxxxxxx>
> > ---
> > hw/i386/x86.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/hw/i386/x86.c b/hw/i386/x86.c
> > index b84840a1bb9..50bf249c700 100644
> > --- a/hw/i386/x86.c
> > +++ b/hw/i386/x86.c
> > @@ -108,6 +108,7 @@ void x86_cpu_new(X86MachineState *x86ms, int64_t apic_id, Error **errp)
> > {
> > Object *cpu = object_new(MACHINE(x86ms)->cpu_type);
> >
> > + object_property_add_child(OBJECT(x86ms), "cpu[*]", OBJECT(cpu));
>
> that will take in account only initial cpus, -device/device_add cpus
> will still go to wherever device_add attaches them (see qdev_set_id)
>
> > if (!object_property_set_uint(cpu, "apic-id", apic_id, errp)) {
> > goto out;
> > }
>
