On Sunday, March 16, 2014 02:08:16 PM Stephane Eranian wrote: > Rafael, > > Thanks for the analysis. > > On Sun, Mar 16, 2014 at 12:55 PM, Borislav Petkov <bp@xxxxxxxxx> wrote: > > On Sat, Mar 15, 2014 at 03:15:04PM +0100, Rafael J. Wysocki wrote: > >> I've just gone throught this. > > > > Thanks. > > > >> So the problem is that we have the PNP "system" driver whose only purpose seems > >> to be to reserve system resources so that the PCI layer doesn't assign them to > >> new devices on hotplug (disclaimer: I didn't invent it, I only read the code and > >> comments in there). > >> > >> It does that for ACPI device objects having the "PNP0C02" and "PNP0C01" IDs. > > > > Right, pnp 00:01 is PNP0C02. > > > >> Apparently, snb_uncore_imc_init_box() steps on a range already reserved by that > >> driver on your box. And this doesn't seem to be a coincidence, because the ACPI > >> device object in question probably *does* correspond to the memory controller > >> that the uncore driver attempts to use. > >> > >> I'm not sure how to address that right now to be honest. Arguably, the PNP > >> "system" driver should be replaced with something saner, but still the > >> resources it claims need to be kept out of reach of the PCI's resource > >> allocation code. > > > > Well, I'm only conjecturing here but there should be a way for the > > uncore code to tell the PNP "system" driver to free this resource > > because uncore is going to use it now. Or something to that effect. > > > I agree. The snb_uncore_imc() is making real (good) use of the device. > It needs to own it. So we need a way to free the resource from the PNP > system or a way to tell PNP need to grab it on systems with the > snb_uncore_imc() support. Does that kind of API exist? > > Where do I look to prevent PNP from grabbing the IMC? drivers/pnp/system.c is the driver in question and system_pnp_probe() makes the reservations via reserve_resources_of_dev(), so you'd need to modify that. I'm not sure what's the right way to go here, though. -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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
