On 06/17/2010 02:35 AM, Jeremy Fitzhardinge wrote: >>> >>> By the way, is there linux kernel limit regarding above 44-bits physical >>> address in x86_32 PAE? For example, pfn above 32-bits is not supported? > > That's an awkward situation. I would tend to suggest that you not > support this type of machine with a 32-bit kernel. Is it a sparse > memory system, or is there a device mapped in that range? > > I guess it would be possible to special-case ioremap to allow the > creation of such mappings, but I don't know what kind of system-wide > fallout would happen as a result. The consequences of something trying > to extract a pfn from one of those ptes would be > >> There are probably places at which PFNs are held in 32-bit numbers, >> although it would be good to track them down if it isn't too expensive >> to fix them (i.e. doesn't affect generic code.) >> > > There are many places which hold pfns in 32 bit variables on 32 bit > systems; the standard type for pfns is "unsigned long", pretty much > everywhere in the kernel. It might be worth defining a pfn_t and > converting usage over to that, but it would be a pervasive change. > I think you're right, and just making 2^44 work correctly would be good enough. Doing special forwarding of all 52 bits of the real physical address in the paravirt case (where it is self-contained and doesn't spill into the rest of the kernel) would probably be a good thing, though. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- 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
