On Tue, Nov 24, 2009 at 03:35:22PM -0800, Jeremy Fitzhardinge wrote:

It would be the easiest way. Unfortunatly the call sequence is the following:

pciback_do_op pciback_enable_msi (dev) ... arch_setup_msi_irqs ... arch_setup_msi_irq ... xen_setup_msi_irqs

The caller of the pciback_enable_msi knows of the domain id, but the rest of the stack does not. One way of doing this is to provide hooks in event.c,
say:

[de|]register_msi_owner

(this is akin to how it was done in 2.6.18.hg)

where the device is associated with a specific domain id. We would call those register/deregister when a new device has changed ownership to a domain.

Back to the call trace. When we reach xen_setup_msi_irqs we can find the
relation. Lookup the device (on this 'registration list') and see if it is assigned to a specific domain.

But in essence it is similar in spirit to the mechanism of the xenbus_walk - that is to find out what domain id is associated with this device.

With the patches posted by Xiantao this behavior would have to be emulated for PCI INTx devices as well, or some flavour of it.

So the question is, Jeremy, would you prefer to have a
'[de|]register_device_owner' call that both MSI and INTx can use and some way of traversing the list this creates and finding out if there is an owner for the device? Or just leave it with the xenbus_walk interface?