Re: [Qemu-devel] [PATCH v1 06/11] pc-dimm: don't allow to access "size" before the device was realized

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 15 Jun 2018 11:25:59 +0200
David Hildenbrand <david@redhat.com> wrote:

> On 15.06.2018 11:16, Igor Mammedov wrote:
> > On Thu, 14 Jun 2018 16:10:14 +0200
> > David Hildenbrand <david@redhat.com> wrote:
> >   
> >> On 14.06.2018 15:24, Igor Mammedov wrote:  
> >>> On Wed, 13 Jun 2018 16:03:35 +0200
> >>> David Hildenbrand <david@redhat.com> wrote:
> >>>     
> >>>> On 13.06.2018 14:56, Igor Mammedov wrote:    
> >>>>> On Mon, 11 Jun 2018 14:16:50 +0200
> >>>>> David Hildenbrand <david@redhat.com> wrote:
> >>>>>       
> >>>>>> "size" should not be queried before the device was realized. Let' make
> >>>>>> that explicit.
> >>>>>>
> >>>>>> Signed-off-by: David Hildenbrand <david@redhat.com>      
> >>>>> It's generic property getter, it should work even before realize is called.      
> >>>>
> >>>> That's the point, as we can see in NVDIMM code , it is *not* a generic
> >>>> property getter.    
> >>> it is added by 
> >>>     object_property_add(obj, PC_DIMM_SIZE_PROP, "uint64", pc_dimm_get_size,      
> >>>                         NULL, NULL, NULL, &error_abort); 
> >>> hence it's generic QOM property as opposed to memory device class specific callbacks.
> >>>     
> >>>>    
> >>>>>
> >>>>> if issues described in 5/11 are properly fixed, this patch won't be needed.
> >>>>>
> >>>>> So drop this patch
> >>>>>
> >>>>>       
> >>>>>> ---
> >>>>>>  hw/mem/pc-dimm.c | 6 ++++++
> >>>>>>  1 file changed, 6 insertions(+)
> >>>>>>
> >>>>>> diff --git a/hw/mem/pc-dimm.c b/hw/mem/pc-dimm.c
> >>>>>> index 86fbcf2d0c..5294734529 100644
> >>>>>> --- a/hw/mem/pc-dimm.c
> >>>>>> +++ b/hw/mem/pc-dimm.c
> >>>>>> @@ -166,6 +166,12 @@ static void pc_dimm_get_size(Object *obj, Visitor *v, const char *name,
> >>>>>>      PCDIMMDevice *dimm = PC_DIMM(obj);
> >>>>>>      PCDIMMDeviceClass *ddc = PC_DIMM_GET_CLASS(obj);
> >>>>>>  
> >>>>>> +    if (!DEVICE(obj)->realized) {
> >>>>>> +        error_setg(errp, "Property \"%s\" not accessible before realized",
> >>>>>> +                   name);
> >>>>>> +        return;
> >>>>>> +    }
> >>>>>> +
> >>>>>>      mr = ddc->get_memory_region(dimm, errp);    
> >>> just make ddc->get_memory_region return error if 'memdev' isn't set yet
> >>> and add local_error handling here as proper property assessor should do.
> >>>     
> >>
> >> Does not help for NVDIMM.  
> > NVDIMM should be fixed as it's broken now and works just by accident.
> > I don't like tailoring infrastructure changes to a particular broken
> > device especially when the later could be made to work within current
> > framework.
> >   
> 
> Yes, but I will go the path of static properties for NVDIMM instead.
> Trying to initialize the memory region in a property setter
> ("label-size") and then bailing out because another property (memdev) is
> not set looks strange. I will do checks+initialization in realize() and
> in get_memory_region(). This looks better in my point of view and looks
> like a nice NVDIMM refactoring (at least judging from the patches I have
> on my list now :) ).
sure, I worry less about how it's implemented inside of device model as
far as it behaves nicely to external user.