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RE: [Xen-devel] [rfc 00/18] ioemu: use devfn instead of slots as the uni

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>, Simon Horman <horms@xxxxxxxxxxxx>, Yuji Shimada <shimada-yxb@xxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [rfc 00/18] ioemu: use devfn instead of slots as the unit for passthrough
From: Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>
Date: Tue, 24 Feb 2009 01:29:48 +0000
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Thread-topic: [Xen-devel] [rfc 00/18] ioemu: use devfn instead of slots as the unit for passthrough
> > That thought crossed my mind too, I will investigate further.
> > But I think that ideally it would need to be expanded to 143
> > as the first 16 GSI are currently reserved for ISA.
> 
> Can't xend or qemu do a search of PCI slot space to pick a virtual
> devfn:intx that doesn't conflict (or that purposely does conflict, if
> there are any cases where you want that)? 32 non-legacy GSIs should be enough
> to avoid any aliasing if a bit of effort is put in to avoid it.

One related issue we need to think about is how we can get some sort of 
consistency over how devices are assigned to slots, so it's possible to add a 
new device and not have all existing ones re-numbered (hence causing the OS to 
hiccup).

Giving devices (both emulated and PT) an optional order parameter in the config 
file which is used to determine the order with which they are allocated 
resources is probably sufficient.

Ian

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