Re: [early RFC] ARM PCI Passthrough design document

["Roger Pau Monné" <roger.pau@citrix.com>]

On Thu, Mar 09, 2017 at 07:29:34PM -0500, Konrad Rzeszutek Wilk wrote:
> On Thu, Mar 09, 2017 at 01:26:45PM +0000, Julien Grall wrote:
> > Hi Konrad,
> > 
> > On 09/03/17 11:17, Konrad Rzeszutek Wilk wrote:
> > > On Thu, Mar 09, 2017 at 11:59:51AM +0900, Roger Pau Monné wrote:
> > > > On Wed, Mar 08, 2017 at 02:12:09PM -0500, Konrad Rzeszutek Wilk wrote:
> > > > > On Wed, Mar 08, 2017 at 07:06:23PM +0000, Julien Grall wrote:
> > > > > .. this as for SR-IOV devices you need the drivers to kick the hardware
> > > > > to generate the new bus addresses. And those (along with the BAR regions) are
> > > > > not visible in ACPI (they are constructued dynamically).
> > > > 
> > > > There's already code in Xen [0] to find out the size of the BARs of SR-IOV
> > > > devices, but I'm not sure what's the intended usage of that, does it need to
> > > > happen _after_ the driver in Dom0 has done whatever magic for this to work?
> > > 
> > > Yes. This is called via the PHYSDEVOP_pci_device_add hypercall when
> > > the device driver in dom0 has finished "creating" the VF. See drivers/xen/pci.c
> > 
> > We are thinking to not use PHYSDEVOP_pci_device_add hypercall for ARM and do
> > the PCI scanning in Xen.
> > 
> > If I understand correctly what you said, only the PCI driver will be able to
> > kick SR-IOV device and Xen would not be able to detect the device until it
> > has been fully configured. So it would mean that we have to keep
> > PHYSDEVOP_pci_device_add around to know when Xen can use the device.
> > 
> > Am I correct?
> 
> Yes. Unless the PCI drivers come up with some other way to tell the
> OS that oh, hey, there is this new PCI device with this BDF.
> 
> Or the underlaying bus on ARM can send some 'new device' information?

Hm, is this something standard between all the SR-IOV implementations, or each
vendors have their own sauce?

Would it be possible to do this SR-IOV initialization inside of Xen, or that
requires ACPI information?

Roger.

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