Re: [PATCH 4/5] spapr: Pass &error_abort when getting some PC DIMM properties

[Greg Kurz <groug@kaod.org>]

On Tue, 27 Oct 2020 12:54:24 +0100
Igor Mammedov <imammedo@redhat.com> wrote:

> On Sun, 25 Oct 2020 16:24:44 +0100
> Greg Kurz <groug@kaod.org> wrote:
> 
> > On Fri, 23 Oct 2020 21:15:09 +0200
> > Igor Mammedov <imammedo@redhat.com> wrote:
> > 
> > > On Mon, 19 Oct 2020 10:48:41 +0200
> > > Greg Kurz <groug@kaod.org> wrote:
> > >   
> > > > Both PC_DIMM_SLOT_PROP and PC_DIMM_ADDR_PROP are defined in the
> > > > default property list of the PC DIMM device class:
> > > > 
> > > >     DEFINE_PROP_UINT64(PC_DIMM_ADDR_PROP, PCDIMMDevice, addr, 0),
> > > > 
> > > >     DEFINE_PROP_INT32(PC_DIMM_SLOT_PROP, PCDIMMDevice, slot,
> > > >                       PC_DIMM_UNASSIGNED_SLOT),
> > > > 
> > > > They should thus be always gettable for both PC DIMMs and NVDIMMs.
> > > > An error in getting them can only be the result of a programming
> > > > error. It doesn't make much sense to propagate the error in this
> > > > case. Abort instead.
> > > > 
> > > > Signed-off-by: Greg Kurz <groug@kaod.org>  
> > > 
> > > Reviewed-by: Igor Mammedov <imammedo@redhat.com>
> > > 
> > > TODO for future,
> > > get rid of local_err in spapr_memory_plug() altogether, it should not fail.
> > > it needs moving check from spapr_drc_attach() to spapr_memory_pre_plug() time.
> > > 
> > > that will clear up (a bit) road for dropping errp in spapr_memory_plug()  
> > 
> > Igor,
> > 
> > I could find time to look a bit into attaching DRCs at pre-plug and I
> > think this isn't possible. The problem is that there doesn't seem to be
> > a reverse operation for pre-plug. If realize fails for the DIMM device,
> > spapr_drc_detach() wouldn't be called, which would be wrong.
> 
> probably I was clear enough, I didn't suggest to move spapr_drc_detach()
> to pre_plug time but rather do a bit of surgery along the lines:
> 

Ok, I get it now. I realize now I actually misread your suggestion. Sorry...

> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 2db810f73a..59a229b4fa 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -3474,6 +3474,11 @@ static void spapr_memory_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
>          return;
>      }
>  
> +    get drc
> +    if (!spapr_drc_attachable(drc)) {
> +        error out
> +    }
> +

It might require some more code refactoring because the way regular
PC-DIMMs are broken down into a set of logical memory blocks (LMBs),
each one having its own DRC but it's certainly doable. Probably for
QEMU 6.0 though since we're entering soft freeze and David already
fired a PR today.

>      if (is_nvdimm) {
>          spapr_nvdimm_validate(hotplug_dev, NVDIMM(dev), size, &local_err);
>          if (local_err) {
> diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c
> index fe998d8108..ae049bc202 100644
> --- a/hw/ppc/spapr_drc.c
> +++ b/hw/ppc/spapr_drc.c
> @@ -371,14 +371,16 @@ static void prop_get_fdt(Object *obj, Visitor *v, const char *name,
>      } while (fdt_depth != 0);
>  }
>  
> -void spapr_drc_attach(SpaprDrc *drc, DeviceState *d, Error **errp)
> +
> +bool spapr_drc_attachable(SpaprDrc *drc)
> +{
> +   return !drc->dev;
> +}
> +
> +void spapr_drc_attach(SpaprDrc *drc, DeviceState *d)
>  {
>      trace_spapr_drc_attach(spapr_drc_index(drc));
>  
> -    if (drc->dev) {
> -        error_setg(errp, "an attached device is still awaiting release");
> -        return;
> -    }
>      g_assert((drc->state == SPAPR_DRC_STATE_LOGICAL_UNUSABLE)
>               || (drc->state == SPAPR_DRC_STATE_PHYSICAL_POWERON));
> 
> > 
> > Am I missing something ?
> > 
> > > > ---
> > > >  hw/ppc/spapr.c |   17 +++--------------
> > > >  1 file changed, 3 insertions(+), 14 deletions(-)
> > > > 
> > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > > index 1b173861152f..62f217a6b914 100644
> > > > --- a/hw/ppc/spapr.c
> > > > +++ b/hw/ppc/spapr.c
> > > > @@ -3443,19 +3443,13 @@ static void spapr_memory_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
> > > >  
> > > >      if (!is_nvdimm) {
> > > >          addr = object_property_get_uint(OBJECT(dimm),
> > > > -                                        PC_DIMM_ADDR_PROP, &local_err);
> > > > -        if (local_err) {
> > > > -            goto out_unplug;
> > > > -        }
> > > > +                                        PC_DIMM_ADDR_PROP, &error_abort);
> > > >          spapr_add_lmbs(dev, addr, size,
> > > >                         spapr_ovec_test(ms->ov5_cas, OV5_HP_EVT),
> > > >                         &local_err);
> > > >      } else {
> > > >          slot = object_property_get_int(OBJECT(dimm),
> > > > -                                       PC_DIMM_SLOT_PROP, &local_err);
> > > > -        if (local_err) {
> > > > -            goto out_unplug;
> > > > -        }
> > > > +                                       PC_DIMM_SLOT_PROP, &error_abort);
> > > >          /* We should have valid slot number at this point */
> > > >          g_assert(slot >= 0);
> > > >          spapr_add_nvdimm(dev, slot, &local_err);
> > > > @@ -3634,7 +3628,6 @@ static void spapr_memory_unplug_request(HotplugHandler *hotplug_dev,
> > > >                                          DeviceState *dev, Error **errp)
> > > >  {
> > > >      SpaprMachineState *spapr = SPAPR_MACHINE(hotplug_dev);
> > > > -    Error *local_err = NULL;
> > > >      PCDIMMDevice *dimm = PC_DIMM(dev);
> > > >      uint32_t nr_lmbs;
> > > >      uint64_t size, addr_start, addr;
> > > > @@ -3650,11 +3643,7 @@ static void spapr_memory_unplug_request(HotplugHandler *hotplug_dev,
> > > >      nr_lmbs = size / SPAPR_MEMORY_BLOCK_SIZE;
> > > >  
> > > >      addr_start = object_property_get_uint(OBJECT(dimm), PC_DIMM_ADDR_PROP,
> > > > -                                         &local_err);
> > > > -    if (local_err) {
> > > > -        error_propagate(errp, local_err);
> > > > -        return;
> > > > -    }
> > > > +                                          &error_abort);
> > > >  
> > > >      /*
> > > >       * An existing pending dimm state for this DIMM means that there is an
> > > > 
> > > > 
> > > >   
> > >   
> > 
>