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Re: [Qemu-ppc] [Qemu-devel] [PATCH] spapr-pci: enable adding PHB via -de
From: |
Alexey Kardashevskiy |
Subject: |
Re: [Qemu-ppc] [Qemu-devel] [PATCH] spapr-pci: enable adding PHB via -device |
Date: |
Tue, 21 Jan 2014 21:00:25 +1100 |
User-agent: |
Mozilla/5.0 (X11; Linux i686 on x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 |
On 01/21/2014 06:56 PM, Markus Armbruster wrote:
> Alexey Kardashevskiy <address@hidden> writes:
>
>> On 01/21/2014 02:27 AM, Markus Armbruster wrote:
>>> Alexey Kardashevskiy <address@hidden> 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 <address@hidden>
>>> 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 <address@hidden>
>>> Reviewed-by: Marcel Apfelbaum <address@hidden>
>>> Signed-off-by: Andreas Färber <address@hidden>
>>>
>>> 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