Re: PCI Pass-through in Xen ARM - Draft 2.

[Ian Campbell <ian.campbell@citrix.com>]

On Fri, 2015-07-31 at 13:16 +0530, Manish Jaggi wrote:
> > > Secondly, the vdev-X entry is created async by dom0 watching on 
> > > event.
> > > So how the tools could read back and call assign device again.
> > Perhaps by using a xenstore watch on that node to wait for the 
> > assignment
> > from pciback to occur.
> As per the flow in the do_pci_add function, assign_device is called 
> first and based on the success xenstore entry is created.
> Are you suggesting to change the sequence.

Perhaps that is what it would take, yes, or maybe some other refactoring
(e.g. splitting assign_device into two stages) might be the answer.

My current preference is for the suggestion below which is to let the
toolstack pick the vdevfn and have pciback honour it.

> We can discuss this more on #xenarm irc

Sorry I missed your ping yesterday, I had already gone home.

> > > > Or you could change things such that vdevfn is always chosen by the
> > > > toolstack for ARM, not optionally like it is on x86.
> > For this one, the struct libxl_device_pci has a field "vdevfn", which 
> > is
> > supposed to allow the user to specify a specific vdevfn. I'm not sure 
> > how
> > that happens or fits together but libxl could undertake to set that on 
> > ARM
> > in the case where the user hasn't done so, effectively taking control 
> > of
> > the PCI bus assignment.
> > 
> > Ian.
> > 
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>