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Re: [Qemu-devel] [PATCH 01/58] spapr: proper qdevification


From: David Gibson
Subject: Re: [Qemu-devel] [PATCH 01/58] spapr: proper qdevification
Date: Thu, 15 Sep 2011 13:14:37 +1000
User-agent: Mutt/1.5.21 (2010-09-15)

On Wed, Sep 14, 2011 at 10:42:25AM +0200, Alexander Graf wrote:
> From: Paolo Bonzini <address@hidden>
> 
> Right now the spapr devices cannot be instantiated with -device,
> because the IRQs need to be passed to the spapr_*_create functions.
> Do this instead in the bus's init wrapper.
> 
> This is particularly important with the conversion from scsi-disk
> to scsi-{cd,hd} that Markus made.  After his patches, if you
> specify a scsi-cd device attached to an if=none drive, the default
> VSCSI controller will not be created and, without qdevification,
> you will not be able to add yours.
> 
> NOTE from agraf: added small compile fix

Thanks for fixing this, Paolo.  Since writing that code, I've realised
it doesn't really fit the model correctly, but haven't gotten around
to fixing it yet.

I will make a later patch to move the irq allocation from the vio bus
to the xics itself, which will matter once we add PCI and/or other
busses.


A question about qdev stuff.  Under PAPR, there is generally only
supposed to be one SCSI target (disk / cd / whatever) per virtual scsi
bus.  But the generic qdev code will, by default, keep assigning
devices to the existing bus until it's full.  Any thoughts on how to
sanely change that behaviour on a per-machine basis?

We'll have a similar problem later on with PCI - PAPR machines usually
only have one device per host bridge, for better isolation.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson



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