On 01/21/2014 06:56 PM, Markus Armbruster wrote: > Alexey Kardashevskiy <a...@ozlabs.ru> writes: > >> On 01/21/2014 02:27 AM, Markus Armbruster wrote: >>> Alexey Kardashevskiy <a...@ozlabs.ru> writes: >>> >>>> Recent changes introduced cannot_instantiate_with_device_add_yet >>>> and removed capability of adding yet another PCI host bridge via >>>> command line for SPAPR platform (POWERPC64 server). >>> >>> Specifically: >>> >>> commit 837d37167dc446af8a91189108b363c04609e296 >>> Author: Markus Armbruster <arm...@redhat.com> >>> Date: Thu Nov 28 17:26:55 2013 +0100 >>> >>> sysbus: Set cannot_instantiate_with_device_add_yet >>> >>> device_add plugs devices into suitable bus. For "real" buses, that >>> actually connects the device. For sysbus, the connections need to be >>> made separately, and device_add can't do that. The device would be >>> left unconnected, and could not possibly work. >>> >>> Quite a few, but not all sysbus devices already set >>> cannot_instantiate_with_device_add_yet in their class init function. >>> >>> Set it in their abstract base's class init function >>> sysbus_device_class_init(), and remove the now redundant assignments >>> from device class init functions. >>> >>> Signed-off-by: Markus Armbruster <arm...@redhat.com> >>> Reviewed-by: Marcel Apfelbaum <marce...@redhat.com> >>> Signed-off-by: Andreas Färber <afaer...@suse.de> >>> >>> Always good to point to specific commits in commit messages instead of >>> hand-waving "recent changes". >> >> >> My bad, I'll do this next time. Just lost myself in that patch series. >> >> >>>> This brings the capability back and puts SPAPR PHB into "bridge" >>>> category. >>> >>> Look, a sysbus device that grabs the resources it needs from its init() >>> callback instead of getting connected to them by the code that creates >>> it! I'm not sure that's proper, but if it works... Maybe Andreas >>> (cc'ed) can advise. >> >> Sorry, I am not following you. SPAPR PHB allocates resources (memory >> regions...) as (for example) E1000 ethernet device does. > > "Resources" was a poor choice of word. > > I'm talking about connections to other devices. An ordinary device on a > proper bus like PCI or USB gets all its connections via its bus. The > "sysbus" doesn't provide any connection opportunities for its devices. > Instead, the connections are made by the code creating the device. > > You tell me "-device spapr-pci-host-bridge" works (with your patch). > That either means it doesn't need any such connections, or it sets them > up itself somehow, or I'm missing something. The first two would be > unusual, the latter not so much :)
It maps itself (MMIO/IO windows) into the guest physical RAM at some predefined addresses which are calculated from its @index property, and that is pretty much it. I am not sure what else connections it might ever need :) The rest is done via platform hyper- or rtas-calls, and this is that connection I guess. -- Alexey
