Re: [PATCH v14 10/11] qapi/s390/cpu topology: POLARITY_CHANGE qapi event

[Pierre Morel]

On 1/12/23 12:52, Thomas Huth wrote:
> On 05/01/2023 15.53, Pierre Morel wrote:
> > When the guest asks to change the polarity this change
> > is forwarded to the admin using QAPI.
> > The admin is supposed to take according decisions concerning
> > CPU provisioning.
>
> I somehow doubt that an average admin will monitor QEMU for such events 
> ... so this rather should be handled by upper layers like libvirt one day?

Yes.

> > Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> > ---
> >   qapi/machine-target.json | 21 +++++++++++++++++++++
> >   hw/s390x/cpu-topology.c  |  2 ++
> >   2 files changed, 23 insertions(+)
> >
> > diff --git a/qapi/machine-target.json b/qapi/machine-target.json
> > index 927618a78f..10235cfb45 100644
> > --- a/qapi/machine-target.json
> > +++ b/qapi/machine-target.json
> > @@ -437,3 +437,24 @@
> >     'returns': ['S390CpuTopology'],
> >     'if': { 'all': [ 'TARGET_S390X', 'CONFIG_KVM' ] }
> >   }
> > +
> > +##
> > +# @POLARITY_CHANGE:
>
> I'd maybe rather call it CPU_POLARITY_CHANGE ... in case "polarity" is 
> one day also used for some other devices.

OK, right.

> > +#
> > +# Emitted when the guest asks to change the polarity.
> > +#
> > +# @polarity: polarity specified by the guest
>
> Please elaborate: Where does the value come from (the PTF instruction)? 
> Which values are possible?

Yes what about:

# @polarity: the guest can specify with the PTF instruction a horizontal
#            or a vertical polarity.
#            On horizontal polarity the host is expected to provision
#            the vCPU equally.
#            On vertical polarity the host can provision each vCPU
#            differently
#            The guest can get information on the provisioning with
#            the STSI(15) instruction.


Regards,
Pierre


--
Pierre Morel
IBM Lab Boeblingen