On a real system with POWER{8,9,10} processors, PHBs are sub-units of
the processor, they can be deactivated by firmware but not plugged in
or out like a PCI adapter on a slot. Nevertheless, having user-created
PHBs in QEMU seemed to be a good idea for testing purposes :
1. having a limited set of PHBs speedups boot time.
2. it is useful to be able to mimic a partially broken topology you
some time have to deal with during bring-up.
PowerNV is also used for distro install tests and having libvirt
support eases these tasks. libvirt prefers to run the machine with
-nodefaults to be sure not to drag unexpected devices which would need
to be defined in the domain file without being specified on the QEMU
command line. For this reason :
3. -nodefaults should not include default PHBs
User-created PHB{3,4,5} devices satisfied all these needs but reality
proves to be a bit more complex, internally when modeling such
devices, and externally when dealing with the user interface.
Req 1. and 2. can be simply addressed differently with a machine option:
"phb-mask=<uint>", which QEMU would use to enable/disable PHB device
nodes when creating the device tree.
For Req 3., we need to make sure we are taking the right approach. It
seems that we should expose a new type of user-created PHB device, a
generic virtualized one, that libvirt would use and not one depending
on the processor revision. This needs more thinking.
For now, remove user-created PHB{3,4,5} devices. All the cleanups we
did are not lost and they will be useful for the next steps.
Fixes: 5bc67b052b ("ppc/pnv: Introduce user creatable pnv-phb4 devices")
Fixes: 1f6a88fffc ("ppc/pnv: Introduce support for user created PHB3 devices")
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220314130514.529931-1-clg@kaod.org>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
9c10d86fee