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

[Manish Jaggi <mjaggi@xxxxxxxxxxxxxxxxxx>]

On Friday 31 July 2015 01:35 PM, Ian Campbell wrote:
> 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.
The hypercall from xenpciback (what I implemented) is actually making 
the assign device in 2 stages.
I think the point of contention is the second stage should be from 
toolstack.
I think calling xc_assign_device after xenstore from the watch callback 
is the only option.
One question is how to split the code for ARM and x86 as this is the 
common code.
Would #ifdef CONFIG_ARM64 ok with maintainers.
> My current preference is for the suggestion below which is to let the
> toolstack pick the vdevfn and have pciback honour it.
That would duplicate code for dev-fn generation into toolstack from 
__xen_pcibk_add_pci_dev.
> > 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.
> > >
> > > _______________________________________________
> > > Xen-devel mailing list
> > > Xen-devel@xxxxxxxxxxxxx
> > > http://lists.xen.org/xen-devel
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