Re: [PATCH v5 0/5] user creatable pnv-phb4 devices

[Daniel Henrique Barboza]

On 3/10/22 15:49, Thomas Huth wrote:
> On 11/01/2022 14.10, Daniel Henrique Barboza wrote:
> > Hi,
> >
> > This version implements Cedric's review suggestions from v4. No
> > drastic design changes were made.
> >
> > Changes from v4:
> > - patches 1,3,5: unchanged
> > - patch 2:
> >    * renamed function to pnv_phb4_xscom_realize()
> >    * pnv4_phb4_xscom_realize() is now called at the end of phb4_realize()
> > - patch 4:
> >    * changed pnv_phb4_get_stack signature to use chip and phb
> >    * added a new helper called pnv_pec_stk_default_phb_realize() to
> > realize the default phb when running with defaults
> > - v4 link: https://lists.gnu.org/archive/html/qemu-devel/2022-01/msg02148.html
> >
> > Daniel Henrique Barboza (5):
> >    ppc/pnv: set phb4 properties in stk_realize()
> >    ppc/pnv: move PHB4 XSCOM init to phb4_realize()
> >    ppc/pnv: turn 'phb' into a pointer in struct PnvPhb4PecStack
> >    ppc/pnv: Introduce user creatable pnv-phb4 devices
> >    ppc/pnv: turn pnv_phb4_update_regions() into static
>
> It's now possible to crash QEMU with the pnv-phb4 device:
>
> $ ./qemu-system-ppc64 -nographic -M powernv9 -device pnv-phb4
> Unexpected error in object_property_try_add() at 
> ../../devel/qemu/qom/object.c:1229:
> qemu-system-ppc64: -device pnv-phb4: attempt to add duplicate property 
> 'pnv-phb4[0]' to object (type 'power9_v2.0-pnv-chip')
> Aborted (core dumped)
>
> Any ideas how to fix this?

Thanks for catching this up.

The issue here is that we're not handling the case where an user adds a 
pnv-phb4 device
when running default settings (no -nodefaults). With default settings we are 
adding all
pnv-phb4 devices that are available to the machine, having no room for any 
additional
user creatable pnv-phb4 devices.

A similar situation happens with the powernv8 machine which errors out with a 
different
error message:

$ ./qemu-system-ppc64 -nographic -M powernv8 -device pnv-phb3
qemu-system-ppc64: -device pnv-phb3: Can't add chassis slot, error -16


Adding all possible phbs by default is a behavior these machines had since they 
were introduced,
and I don't think we want to change it. Thus, a fix would be to forbid user 
created pnv-phb devices
when running with defaults.


I'll see what I can do. Thanks,



Daniel


>   Thomas