Re: 2.6.25-rc8-mm1 panic in rpaphp_register_slot()

[Badari Pulavarty]

Andrew Morton wrote:
> On Mon, 7 Apr 2008 17:42:55 -0600
> Alex Chiang <achiang@xxxxxx> wrote:
>
>   
> > Hi Badari,
> >
> >     
> > > > > pci_hotplug: PCI Hot Plug PCI Core version: 0.5
> > > > > rpaphp: RPA HOT Plug PCI Controller Driver version: 0.1
> > > > > rpaphp_register_slot registering slot:path[/pci@800000020000003/pci@2,4] index[22010003], name[U787E.001.AAA3015-P2-C1] pdomain[22010003] type[16]
> > > > > Unable to handle kernel paging request for data at address 0x00000070
> > > > >           
> > > > Hrm, this is a little more information, but still not quite
> > > > enough. I'm going to take a stab in the dark and say I'm probably
> > > > doing something wrong on this line, maybe dereferencing a pointer
> > > > incorrectly:
> > > >
> > > >         retval = pci_hp_register(php_slot, slot->bus,
> > > > 				 PCI_SLOT(PCI_DN(slot->dn->child)->devfn));
> > > >         
> > > Sorry. I thought you knew this already. Disassembly clearly showed
> > > that slot->dn->child is NULL. 
> > >
> > > I confirmed it by adding printk also.
> > >       
> > This patch is a complete guess on my part (since I've not been
> > able to understand pseries architecture) but I think it should
> > fix your issue.
> >
> > Can you give it a try and let me know? It applies on top of the
> > -mm tree that includes my physical pci_slot series.
> >
> > Also, I'm hoping Linas will speak up and let me know what the
> > real answer might be. ;)
> >
> > Thanks.
> >
> > /ac
> >
> > From: Alex Chiang <achiang@xxxxxx>
> > Subject: rpaphp: correctly call pci_hp_register for empty PCI slots
> >
> > Unpopulated device_node slots do not have children, and
> > attempting to dereference them will result in a panic.
> >
> > Instead, attempt to derive the PCI slot number from the bus
> > itself, and failing that, default to 0.
> >
> > Signed-off-by: Alex Chiang <achiang@xxxxxx>
> > ---
> > diff --git a/drivers/pci/hotplug/rpaphp_slot.c b/drivers/pci/hotplug/rpaphp_slot.c
> > index 0d4cfc7..91ce6a6 100644
> > --- a/drivers/pci/hotplug/rpaphp_slot.c
> > +++ b/drivers/pci/hotplug/rpaphp_slot.c
> > @@ -121,6 +121,7 @@ int rpaphp_register_slot(struct slot *slot)
> >  {
> >  	struct hotplug_slot *php_slot = slot->hotplug_slot;
> >  	int retval;
> > +	int slot_nr;
> >  
> >  	dbg("%s registering slot:path[%s] index[%x], name[%s] pdomain[%x] type[%d]\n", 
> >  		__FUNCTION__, slot->dn->full_name, slot->index, slot->name, 
> > @@ -132,8 +133,11 @@ int rpaphp_register_slot(struct slot *slot)
> >  		return -EAGAIN;
> >  	}	
> >  
> > -	retval = pci_hp_register(php_slot, slot->bus,
> > -				 PCI_SLOT(PCI_DN(slot->dn->child)->devfn));
> > +	if (slot->bus->self)
> > +		slot_nr = PCI_SLOT(slot->bus->self->devfn);
> > +	else
> > +		slot_nr = 0;
> > +	retval = pci_hp_register(php_slot, slot->bus, slot_nr);
> >  	if (retval) {
> >  		err("pci_hp_register failed with error %d\n", retval);
> >  		return retval;
> >     
>
> Did we hear back from Badari on this?
>
> Thanks.
>   
No. It didn't help. I had to hack "slot_nr = 0" all the time to boot my 
machine.

I was trying to get some ppc expert to review the patch, as Alex was not
comfortable with the fix/hack. Linas is no longer with IBM :(

Thanks,
Badari

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