Re: [PATCH v1] s390x/kvm: Set default cpu model for all machine classes

[David Hildenbrand]

On 21.10.19 11:52, Thomas Huth wrote:
> On 21/10/2019 11.34, David Hildenbrand wrote:
> > We have to set the default model of all machine classes, not just for
> > the active one. Otherwise, "query-machines" will indicate the wrong
> > CPU model ("qemu-s390x-cpu" instead of "host-s390x-cpu") as
> > "default-cpu-type".
> >
> > Doing a
> >      {"execute":"query-machines"}
> > under KVM now results in
> >      {"return": [
> >          {
> >              "hotpluggable-cpus": true,
> >              "name": "s390-ccw-virtio-4.0",
> >              "numa-mem-supported": false,
> >              "default-cpu-type": "host-s390x-cpu",
> >              "cpu-max": 248,
> >              "deprecated": false},
> >          {
> >              "hotpluggable-cpus": true,
> >              "name": "s390-ccw-virtio-2.7",
> >              "numa-mem-supported": false,
> >              "default-cpu-type": "host-s390x-cpu",
> >              "cpu-max": 248,
> >              "deprecated": false
> >          } ...
> >
> > Reported-by: Jiri Denemark <address@hidden>
> > Fixes: b6805e127c6b ("s390x: use generic cpu_model parsing")
> > Cc: Igor Mammedov <address@hidden>
> > Signed-off-by: David Hildenbrand <address@hidden>
> > ---
> >   target/s390x/kvm.c | 10 ++++++++--
> >   1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> > index c24c869e77..5966ab0d37 100644
> > --- a/target/s390x/kvm.c
> > +++ b/target/s390x/kvm.c
> > @@ -320,11 +320,17 @@ void kvm_s390_set_max_pagesize(uint64_t pagesize, Error 
> > **errp)
> >       cap_hpage_1m = 1;
> >   }
> >   
> > -int kvm_arch_init(MachineState *ms, KVMState *s)
> > +static void ccw_machine_class_foreach(ObjectClass *klass, void *opaque)
> >   {
> > -    MachineClass *mc = MACHINE_GET_CLASS(ms);
> > +    MachineClass *mc = MACHINE_CLASS(klass);
>
> I think we rather wanted to avoid using "klass" in new code... maybe use
> "oc" instead of "klass" ?

Can do, this was a copy and paste :)

> >       mc->default_cpu_type = S390_CPU_TYPE_NAME("host");
> > +}
> > +
> > +int kvm_arch_init(MachineState *ms, KVMState *s)
> > +{
> > +    object_class_foreach(ccw_machine_class_foreach, TYPE_S390_CCW_MACHINE,
> > +                         false, NULL);
> >   
> >       if (!kvm_check_extension(kvm_state, KVM_CAP_DEVICE_CTRL)) {
> >           error_report("KVM is missing capability KVM_CAP_DEVICE_CTRL - "
>
> Weird, if you start an older machine, you still get the "host" CPU
> without your patch, too:
>
> echo -e "info qom-tree \n quit" | \
>   qemu-system-s390x -display none -monitor stdio -no-shutdown \
>     -accel kvm -M s390-ccw-virtio-3.0 | grep s390x-cpu
>
> Results in:
>
>      /device[0] (host-s390x-cpu)
>
> ... so I wonder why that differs from the "query-machines" command?

query-machines probes with the "none" machine all other machines. 
Current code only fixes up the active machine.

(that's why you won't notice when starting a machine - you will always 
get "host" for the active one)

> Anyway, your patch sounds fine, so (with "klass" replaced by "oc"):
>
> Reviewed-by: Thomas Huth <address@hidden>


--

Thanks,

David / dhildenb