Re: [Xen-devel] [RFC 06/19] xen/arm: Implement hypercall PHYSDEVOP_map_pirq

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-07-15 at 14:01 +0100, Julien Grall wrote:
> >>> Do we think it is the case that we are eventually going to need a guest
> >>> cfg option pci = 0|1? I think the answer is yes. Assinging a pci device
> >>> would cause pci=1, or you can set pci=1 to enable hotplug of pci devices
> >>> later (i.e. mmio space is reserved, INTx interrupts are assigned etc).
> >>
> >> I'm not sure to understand what we would need a "pci" cfg option... For
> >> now, this series doesn't aim to support PCI. So I think we could defer
> >> this problem later.
> >
> > Yeah, we got onto PCI somehow.
> >
> > So long as we are happy not being able to hotplug platform devices I
> > think we don't need an equivalent option (the point would be to only
> > setup huge numbers of SPIs, reserve MMIO space etc if it was going to be
> > used).
> 
> We can reuse the number of IRQs used by the HW. The current series 
> allocates SPIs for guest even if we don't plan to passthrough a device. 
> Are we fine with this drawback for Xen 4.5?

I meant no need for an equivalent user facing option. I'd much prefer it
if the toolstack did the Right Thing and configured the number of SPIs
for each guest at domain build time, based on its knowledge of the
devices configured for passthrough.

Ian.


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