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Re: [Qemu-devel] [PATCH] spapr-pci: enable adding PHB via -device
From: |
Alexey Kardashevskiy |
Subject: |
Re: [Qemu-devel] [PATCH] spapr-pci: enable adding PHB via -device |
Date: |
Tue, 21 Jan 2014 12:37:10 +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 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.
>> This is not much use for emulated PHB but it is absolutely required
>> for VFIO as we put an IOMMU group onto a separate PHB on SPAPR.
>>
>> Cc: Markus Armbruster <address@hidden>
>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>> ---
>>
>> Are -device and device_add considered synonims? SPAPR PHB can be added
>> via the command line just fine but cannot from device_add as
>> "Bus 'main-system-bus' does not support hotplugging".
>
> -device is cold plug, device_add is hot plug. device_add could be
> improved to do cold plug when used before the machine starts.
Soooo? We figured that out on IRC :) At the moment it is regression -
-device used to work for PHB and now it does not.
Alex Graf applied to his ppc-next, just to be clear - are you ack'ing or
nack'ing this patch?
In any cace, what do you think I should change in what I do in spapr_pci.c?
I most probably will, just need some directions.
--
Alexey