On Tue, 2013-08-20 at 08:42 +1000, Benjamin Herrenschmidt wrote: > On Mon, 2013-08-19 at 14:02 -0600, Bjorn Helgaas wrote: > > I guess. And supply the pci_slot rather than the pci_dev? I'm a > > little bit worried because the idea of a "slot" is not well-defined in > > the spec, and we have sort of an ad hoc method of discovering and > > managing them, e.g., acpiphp and pciehp might discover the same slot. > > But I guess that's no reason to bury generic code in vfio. > > And I don't have pci_slot's at all yet on powerpc "powernv" (the host > platform for KVM) since at this stage we don't support physical hotplug > on the target machines... > > Alex, why specifically looking for "slots" here ? I don't quite > understand. It makes sense to be able to reset individual devices > whether they are on the otherboard, behind extension chassis or directly > on slots... a) resetting a slot may have a smaller footprint than resetting a bus, b) hotplug controllers sometimes need to be involved in a bus reset. For b) I have a specific example where my Lenovo S20 workstation has an onboard tg3 NIC attached to a root port supporting pciehp (go figure since the tg3 is soldered onto the motherboard) and doing a secondary bus reset at the root port triggers a presence detection change and therefore tries to do a surprise removal. By doing a "slot" reset, I have the hotplug controller code manage the bus reset by disabling presence detection around the bus reset. If you don't have slots and you don't need anything special around a secondary bus reset, you're fine. It's just an opportunity to provide a hook for the hotplug controller to participate. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
