On Mon, 26 Apr 2010 14:12:35 -0700 "H. Peter Anvin" <hpa@xxxxxxxxx> wrote: > > On Mon, 26 Apr 2010 14:27:56 -0600 > > Bjorn Helgaas <bjorn.helgaas@xxxxxx> wrote: > >> I'm a little concerned that those patches are a sledgehammer approach. > >> Previously, IORESOURCE_BUSY has basically been used for mutual exclusion > >> between drivers that would otherwise claim the same resource. It hasn't > >> been used to guide resource assignment in the PCI/PNP/etc core. Maybe > >> it's a good idea to also use IORESOURCE_BUSY there, but I'm not sure. > >> Right now it feels like undesirable overloading to me. > > > > I guess that's true, removing those regions from the pool entirely > > might be better? Or some other, clear way of expressing that the > > regions aren't available to drivers. Maybe we need a new IO resource > > type for platform ranges. > > > >> I think it also leads to at least one problem: Guenter's machine has no > >> VGA but has a PCI device that lives at 0xa0000. The driver for that > >> device won't be able to request that region if the arch code has marked > >> it busy. > > > > Ah good point, so we'll want another approach at any rate. Yinghai? > > What we need is to keep track of the areas available for address space > allocation by dynamically addressed devices, as distinct from address > space that is in use by a kernel-known device. There is an in-between, > which one can call "here there be dragons" space, which should never be > used for dynamic device allocation, but if a platform device or > pre-assigned device uses that space then it should be allowed to be > allocated. > > In the case of x86, anything that is E820_RESERVED, *or* in the legacy > region (below 1 MB) and is not RAM, is "here there be dragons" space. Agreed. The trickier part is handling any platform devices that request_resource against that space. But maybe we don't need to do anything special; just making sure we avoid it in the PCI "BIOS" code as Bjorn did may be sufficient. -- Jesse Barnes, 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
