Re: [Xen-devel] RFC: [PATCH 1/3] Enhance platform support for PCI

[Manish Jaggi <mjaggi@xxxxxxxxxxxxxxxxxx>]

On 23/02/15 8:45 pm, Julien Grall wrote:
> On 23/02/15 11:50, Manish Jaggi wrote:
> > On 23/02/15 4:44 pm, Julien Grall wrote:
> > > On 23/02/2015 10:59, Manish Jaggi wrote:
> > > > On 20/02/15 8:09 pm, Ian Campbell wrote:
> > > > > On Fri, 2015-02-20 at 19:44 +0530, Manish Jaggi wrote:
> > > > > > > Another option might be a new hypercall (assuming one doesn't already
> > > > > > > exist) to register a PCI bus which would take e.g. the PCI CFG base
> > > > > > > address and return a new u16 segment id to be used for all subsequent
> > > > > > > PCI related calls. This would require the dom0 OS to hook its
> > > > > > > pci_bus_add function, which might be doable (more doable than
> > > > > > > handling
> > > > > > > xen_segment_id DT properties I think).
> > > > > > This seems ok, i will try it out.
> > > > > I recommend you let this subthread (e.g. the conversation with Jan)
> > > > > settle upon a preferred course of action before implementing any one
> > > > > suggestion.
> > > > Ian we have also to consider for NUMA / multi node where there are two
> > > > or more its nodes.
> > > > pci0{
> > > >
> > > > msi-parent = <&its0>;
> > > > }
> > > >
> > > > pci1{
> > > >
> > > > msi-parent = <&its1>;
> > > > }
> > > >
> > > > This requires parsing pci nodes in xen and create a mapping between pci
> > > > nodes and its. Xe would need to be aware of PCI nodes in device tree
> > > > prior to dom0 sending a hypercall. Adding a property to pci node in
> > > > device tree should be a good approach.
> > > Why do you need it early? Wouldn't be sufficient to retrieve those
> > > information when the hypercall pci_device_add is called?
> > The dom0/U device tree should have one 1 its node, xen should map to
> > specific its when trapped.
> The DOM0 device tree should expose the same layout as the hardware. By
> exposing only one ITS you make your life more complicate.
in what way?
> PHYSDEVOP_pci_device_add should be called before any initialization is
> done. Therefore ITS should be configured for this PCI after Xen is aware
> of the PCI.
That is for a device, I believe all devices on a host bridge are 
serviced by a single ITS
> IHMO, any ITS trap before this is wrong.
AFAIK guest always sees a virtual ITS, could you please explain what is 
wrong in trapping.
> Regards,

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