[v2] ppc: Consolidate QOM links and pointers to the same object

[PATCH v2 for-5.0 0/8] ppc: Consolidate QOM links and pointers to the same object

Posted by Greg Kurz 4 years, 5 months ago

There's a recurring pattern in the code where a const link is added to a
newly instanciated object and the link is then used in the object's realize
function to keep a pointer to the QOM entity which the link points to.

void create_obj_b(Object *obj_a)
{
    Object *obj_b;

    obj_b = object_new(TYPE_B);
    object_property_add_const_link(obj_b, "link-to-a", obj_a, &error_abort);
    object_property_set_bool(obj_b, true, "realized", &error_abort);
}

void object_b_realize(DeviceState *dev, Error **errp)
{
    Object *obj_a;

    obj_a = object_property_get_link(OBJECT(dev), "link-to-a", errp);
    if (!obj_a) {
        return;
    }

    obj_b->obj_a = A(obj_a); // If obj_b->obj_a is changed, the link property
                             // still points to the original obj_a that was
                             // passed to object_property_add_const_link()
}

Confusing bugs could arise if the pointer and the link go out of sync for
some reason. This can be avoided if the property is defined to directly use
the pointer with the DEFINE_PROP_LINK() macro.

This series just does that for all occurences of the fragile pattern in
the XIVE and PNV code.

Changes in v2:
- use DEFINE_PROP_LINK() instead of object_property_add_link()
- dropped public -> private changes in type definitions

--
Greg

---

Greg Kurz (8):
      xive: Link "cpu" property to XiveTCTX::cs pointer
      xive: Link "xive" property to XiveSource::xive pointer
      xive: Link "xive" property to XiveEndSource::xrtr pointer
      ppc/pnv: Link "psi" property to PnvLpc::psi pointer
      ppc/pnv: Link "psi" property to PnvOCC::psi pointer
      ppc/pnv: Link "chip" property to PnvHomer::chip pointer
      ppc/pnv: Link "chip" property to PnvCore::chip pointer
      ppc/pnv: Link "chip" property to PnvXive::chip pointer


 hw/intc/pnv_xive.c   |   21 +++++++--------------
 hw/intc/spapr_xive.c |    8 ++++----
 hw/intc/xive.c       |   48 +++++++++++++++---------------------------------
 hw/ppc/pnv.c         |   32 ++++++++++++++++----------------
 hw/ppc/pnv_core.c    |   10 ++--------
 hw/ppc/pnv_homer.c   |   20 ++++++++++----------
 hw/ppc/pnv_lpc.c     |   19 ++++++++-----------
 hw/ppc/pnv_occ.c     |   20 +++++++++-----------
 hw/ppc/pnv_psi.c     |    3 +--
 9 files changed, 72 insertions(+), 109 deletions(-)

Re: [PATCH v2 for-5.0 0/8] ppc: Consolidate QOM links and pointers to the same object

Posted by David Gibson 4 years, 5 months ago

On Fri, Nov 15, 2019 at 04:55:21PM +0100, Greg Kurz wrote:
> There's a recurring pattern in the code where a const link is added to a
> newly instanciated object and the link is then used in the object's realize
> function to keep a pointer to the QOM entity which the link points to.
> 
> void create_obj_b(Object *obj_a)
> {
>     Object *obj_b;
> 
>     obj_b = object_new(TYPE_B);
>     object_property_add_const_link(obj_b, "link-to-a", obj_a, &error_abort);
>     object_property_set_bool(obj_b, true, "realized", &error_abort);
> }
> 
> void object_b_realize(DeviceState *dev, Error **errp)
> {
>     Object *obj_a;
> 
>     obj_a = object_property_get_link(OBJECT(dev), "link-to-a", errp);
>     if (!obj_a) {
>         return;
>     }
> 
>     obj_b->obj_a = A(obj_a); // If obj_b->obj_a is changed, the link property
>                              // still points to the original obj_a that was
>                              // passed to object_property_add_const_link()
> }
> 
> Confusing bugs could arise if the pointer and the link go out of sync for
> some reason. This can be avoided if the property is defined to directly use
> the pointer with the DEFINE_PROP_LINK() macro.
> 
> This series just does that for all occurences of the fragile pattern in
> the XIVE and PNV code.
> 
> Changes in v2:
> - use DEFINE_PROP_LINK() instead of object_property_add_link()
> - dropped public -> private changes in type definitions

Applied to ppc-for-5.0.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

Re: [PATCH v2 for-5.0 0/8] ppc: Consolidate QOM links and pointers to the same object

Posted by Markus Armbruster 4 years, 5 months ago

Greg Kurz <groug@kaod.org> writes:

> There's a recurring pattern in the code where a const link is added to a
> newly instanciated object and the link is then used in the object's realize
> function to keep a pointer to the QOM entity which the link points to.
>
> void create_obj_b(Object *obj_a)
> {
>     Object *obj_b;
>
>     obj_b = object_new(TYPE_B);
>     object_property_add_const_link(obj_b, "link-to-a", obj_a, &error_abort);
>     object_property_set_bool(obj_b, true, "realized", &error_abort);
> }
>
> void object_b_realize(DeviceState *dev, Error **errp)
> {
>     Object *obj_a;
>
>     obj_a = object_property_get_link(OBJECT(dev), "link-to-a", errp);
>     if (!obj_a) {
>         return;
>     }
>
>     obj_b->obj_a = A(obj_a); // If obj_b->obj_a is changed, the link property
>                              // still points to the original obj_a that was
>                              // passed to object_property_add_const_link()
> }
>
> Confusing bugs could arise if the pointer and the link go out of sync for
> some reason. This can be avoided if the property is defined to directly use
> the pointer with the DEFINE_PROP_LINK() macro.
>
> This series just does that for all occurences of the fragile pattern in
> the XIVE and PNV code.

Have you looked for the pattern elsewhere?

Re: [PATCH v2 for-5.0 0/8] ppc: Consolidate QOM links and pointers to the same object

Posted by Cédric Le Goater 4 years, 5 months ago

On 18/11/2019 10:26, Markus Armbruster wrote:
> Greg Kurz <groug@kaod.org> writes:
> 
>> There's a recurring pattern in the code where a const link is added to a
>> newly instanciated object and the link is then used in the object's realize
>> function to keep a pointer to the QOM entity which the link points to.
>>
>> void create_obj_b(Object *obj_a)
>> {
>>     Object *obj_b;
>>
>>     obj_b = object_new(TYPE_B);
>>     object_property_add_const_link(obj_b, "link-to-a", obj_a, &error_abort);
>>     object_property_set_bool(obj_b, true, "realized", &error_abort);
>> }
>>
>> void object_b_realize(DeviceState *dev, Error **errp)
>> {
>>     Object *obj_a;
>>
>>     obj_a = object_property_get_link(OBJECT(dev), "link-to-a", errp);
>>     if (!obj_a) {
>>         return;
>>     }
>>
>>     obj_b->obj_a = A(obj_a); // If obj_b->obj_a is changed, the link property
>>                              // still points to the original obj_a that was
>>                              // passed to object_property_add_const_link()
>> }
>>
>> Confusing bugs could arise if the pointer and the link go out of sync for
>> some reason. This can be avoided if the property is defined to directly use
>> the pointer with the DEFINE_PROP_LINK() macro.
>>
>> This series just does that for all occurences of the fragile pattern in
>> the XIVE and PNV code.
> 
> Have you looked for the pattern elsewhere?

I can take care of the Aspeed machine. I followed the same pattern there.

C.

Re: [PATCH v2 for-5.0 0/8] ppc: Consolidate QOM links and pointers to the same object

Posted by Greg Kurz 4 years, 5 months ago

On Mon, 18 Nov 2019 10:26:12 +0100
Markus Armbruster <armbru@redhat.com> wrote:

> Greg Kurz <groug@kaod.org> writes:
> 
> > There's a recurring pattern in the code where a const link is added to a
> > newly instanciated object and the link is then used in the object's realize
> > function to keep a pointer to the QOM entity which the link points to.
> >
> > void create_obj_b(Object *obj_a)
> > {
> >     Object *obj_b;
> >
> >     obj_b = object_new(TYPE_B);
> >     object_property_add_const_link(obj_b, "link-to-a", obj_a, &error_abort);
> >     object_property_set_bool(obj_b, true, "realized", &error_abort);
> > }
> >
> > void object_b_realize(DeviceState *dev, Error **errp)
> > {
> >     Object *obj_a;
> >
> >     obj_a = object_property_get_link(OBJECT(dev), "link-to-a", errp);
> >     if (!obj_a) {
> >         return;
> >     }
> >
> >     obj_b->obj_a = A(obj_a); // If obj_b->obj_a is changed, the link property
> >                              // still points to the original obj_a that was
> >                              // passed to object_property_add_const_link()
> > }
> >
> > Confusing bugs could arise if the pointer and the link go out of sync for
> > some reason. This can be avoided if the property is defined to directly use
> > the pointer with the DEFINE_PROP_LINK() macro.
> >
> > This series just does that for all occurences of the fragile pattern in
> > the XIVE and PNV code.
> 
> Have you looked for the pattern elsewhere?
> 

No I was focusing on the XICS/XIVE interrupt controller code for PPC machines
only. I'll have a broader look.