Re: [PATCH v1 1/9] s390x: smp: s390x dedicated smp parsing

[Pierre Morel]

On 7/16/21 10:54 AM, Cornelia Huck wrote:
> On Wed, Jul 14 2021, Pierre Morel <pmorel@linux.ibm.com> wrote:
>
> > We need a s390x dedicated SMP parsing to handle s390x specificities.
> >
> > In this patch we only handle threads, cores and sockets for
> > s390x:
> > - do not support threads, we always have 1 single thread per core
> > - the sockets are filled one after the other with the cores
> >
> > Both these handlings are different from the standard smp_parse
> > functionement and reflect the CPU topology in the simple case
> > where all CPU belong to the same book.
> >
> > Topology levels above sockets, i.e. books, drawers, are not
> > considered at this stage and will be introduced in a later patch.
> >
> > Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> > ---
> >   hw/s390x/s390-virtio-ccw.c | 42 ++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 42 insertions(+)
> >
> > diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> > index e4b18aef49..899d3a4137 100644
> > --- a/hw/s390x/s390-virtio-ccw.c
> > +++ b/hw/s390x/s390-virtio-ccw.c
> > @@ -582,6 +582,47 @@ static ram_addr_t s390_fixup_ram_size(ram_addr_t sz)
> >       return newsz;
> >   }
> >   
> > +/*
> > + * In S390CCW machine we do not support threads for now,
> > + * only sockets and cores.
> > + */
> > +static void s390_smp_parse(MachineState *ms, QemuOpts *opts)
>
> It seems you based this on an older version of the code? The current
> signature of this function since 1e63fe685804 ("machine: pass QAPI
> struct to mc->smp_parse") is
>
> void (*smp_parse)(MachineState *ms, SMPConfiguration *config, Error **errp);
>
> That affects your parsing, and also lets you get rid of the ugly exit(1)
> statements.

hum, yes, thanks

> > +{
> > +    unsigned cpus    = qemu_opt_get_number(opts, "cpus", 1);
> > +    unsigned sockets = qemu_opt_get_number(opts, "sockets", 1);
> > +    unsigned cores   = qemu_opt_get_number(opts, "cores", 1);
> > +
> > +    if (opts) {
> > +        if (cpus == 0 || sockets == 0 || cores == 0) {
>
> This behaviour looks different from what we do for other targets: if you
> specify the value as 0, a value is calculated from the other values;
> here, you error out. It's probably not a good idea to differ.

right, thanks

> > +            error_report("cpu topology: "
> > +                         "sockets (%u), cores (%u) or number of CPU(%u) "
> > +                         "can not be zero", sockets, cores, cpus);
> > +            exit(1);
> > +        }
> > +    }
> > +

--
Pierre Morel
IBM Lab Boeblingen