On Mon, Jan 20, 2014 at 12:24 PM, Michael Roth <mdr...@linux.vnet.ibm.com> wrote: > Quoting Alexey Kardashevskiy (2014-01-19 20:58:20) > > Would need to look at it a bit more closely to say for certain, but after > discussing it a bit Tyrel/Mike, I think the main considerations would be: > > 1) PHB hotplug/unplug would need to signal a different event type in it's > check-exception/epow message, we have stubs in place for a PHB event type, > so that's mostly a matter of adding special-casing in the hotplug callback > for spapr-pci-host-bridge devices > 2) The required properties for the OF node corresponding PHB will be > different. > Currently these are generated as part of the hotplug callback, and attached > to the corresponding ConfigureConnectorState node to be fed to the guest > via subsequent ibm,configure-connector RTAS calls, so we'd just hook the > PHB's OF node generation code in there as. > 3) The sysctl/kernel interface for handling PHB hotplug would be different, > we'd be relying on the rpadlar kernel module > (/sys/bus/pci/slots/control/add_slot) rather than rpaphp > (/sys/bus/pci/slots/<slot>/power) or the PCI rescan fallback. > This is mostly a matter of modifying the handling in the guest tools, > namely > in rtas_errd, to handle the event accordingly. > > We also haven't done anything extensive using rpadlpar operations within qemu > guests, so there may be various odds/ends and possibly kernel changes needed > to > get that working properly (as was the case for rpaphp, though thanks to the > PCI > rescan workaround a new kernel isn't required for existing guests... a similar > fallback likely won't be available for rpadlpar) > > But from a high-level view at least it seems fairly straight-forward. I'll see > if we can get a prototype working.
The fact that it "just works" now by rescanning the pci filesystem is a significant benefit. I don't think we want to lose it. There can be many PHBs on one of these systems. Maybe we could make the PHB hot-pluggable and also always have one PHB plugged in at startup. Then the guest will see the bus when it starts and it will build the pci file system. Mike
