On Mon, 2011-06-13 at 16:34 -0500, Jon Mason wrote: > For PCIE hotplug enabled slots not connected directly to a PCI-E root > port, there can be problems when hotplugging devices. This is due to > the possibility of hotplugging a device into the fabric with a smaller > MPS that the devices currently running have configured. Modifying the > MPS on the running devices could cause a fatal bus error due to an > incoming frame being larger than the newly configured MPS. To work > around this, the MPS for the entire fabric must be set to the minimum > size. Any devices hotplugged into this fabric will have the minimum MPS > set. If the PCI hotplug slot is directly connected to the root port and > there are not other devices on the fabric (which seems to be the most > common case), then this is not an issue and MPS discovery will occur as > normal. Well, this is sub-optimal.... it would be nice if we could have some arch control on that stuff. For example, on bare metal Power, I'd like to do like our hypervisor, which assumes we don't do device -> device transfers and that our host bridges never generate >cache line request. That means that the "upstream" MPS doesn't matter, all is needed is to keep the hotplugged device one below its parent and all should be good. Cheers, Ben. -- 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
