Re: [PATCH 2/2] numa: properly check if numa is supported

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 13 Dec 2019 09:33:10 +0800
Tao Xu <tao3.xu@intel.com> wrote:

> On 12/12/2019 8:48 PM, Igor Mammedov wrote:
> > Commit aa57020774b, by mistake used MachineClass::numa_mem_supported
> > to check if NUMA is supported by machine and also as unrelated change
> > set it to true for sbsa-ref board.
> > 
> > Luckily change didn't break machines that support NUMA, as the field
> > is set to true for them.
> > 
> > But the field is not intended for checking if NUMA is supported and
> > will be flipped to false within this release for new machine types.
> > 
> > Fix it:
> >   - by using previously used condition
> >        !mc->cpu_index_to_instance_props || !mc->get_default_cpu_node_id
> >     the first time and then use MachineState::numa_state down the road
> >     to check if NUMA is supported
> >   - dropping stray sbsa-ref chunk
> > 
> > Fixes: aa57020774b690a22be72453b8e91c9b5a68c516
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > ---
> > CC: Radoslaw Biernacki <radoslaw.biernacki@linaro.org>
> > CC: Peter Maydell <peter.maydell@linaro.org>
> > CC: Leif Lindholm <leif.lindholm@linaro.org>
> > CC: qemu-arm@nongnu.org
> > CC: qemu-stable@nongnu.org
> > 
> > 
> >   hw/arm/sbsa-ref.c | 1 -
> >   hw/core/machine.c | 4 ++--
> >   2 files changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/hw/arm/sbsa-ref.c b/hw/arm/sbsa-ref.c
> > index 27046cc..c6261d4 100644
> > --- a/hw/arm/sbsa-ref.c
> > +++ b/hw/arm/sbsa-ref.c
> > @@ -791,7 +791,6 @@ static void sbsa_ref_class_init(ObjectClass *oc, void *data)
> >       mc->possible_cpu_arch_ids = sbsa_ref_possible_cpu_arch_ids;
> >       mc->cpu_index_to_instance_props = sbsa_ref_cpu_index_to_props;
> >       mc->get_default_cpu_node_id = sbsa_ref_get_default_cpu_node_id;
> > -    mc->numa_mem_supported = true;
> >   }
> >   
> >   static const TypeInfo sbsa_ref_info = {
> > diff --git a/hw/core/machine.c b/hw/core/machine.c
> > index 1689ad3..aa63231 100644
> > --- a/hw/core/machine.c
> > +++ b/hw/core/machine.c
> > @@ -958,7 +958,7 @@ static void machine_initfn(Object *obj)
> >                                           NULL);
> >       }
> >   
> > -    if (mc->numa_mem_supported) {
> > +    if (mc->cpu_index_to_instance_props && mc->get_default_cpu_node_id) {
> >           ms->numa_state = g_new0(NumaState, 1);
> >       }  
> 
> I am wondering if @numa_mem_supported is unused here, it is unused for 
> QEMU, because the only usage of @numa_mem_supported is to initialize 
> @numa_state. Or there is other usage? So should it be removed from 
> struct MachineClass?
You are wrong, it's not intended for numa_state initialization,
read doc comment for it in include/hw/boards.h
(for full story look at commit cd5ff8333a3)