Yinghai Lu wrote: >>> >> OK. This is starting to make sense. I suspect this is a similar issue >> as 3b0fde0fac19c180317eb0601b3504083f4b9bf5 addresses, which is that the >> e820 code assumes -- and I don't see any exception to that in >> 45fbe3ee01b8e463b28c2751b5dcc0cbdc142d90 -- that iomem_resource covers >> the entire 64-bit address space that e820 knows. I wonder what happens >> with "interestingly shaped" memory above 4 GB if resource_size_t is 32 >> bits with that code. >> >> In terms of address space assignment, an alternate implementation of the >> address space cap is to mark it reserved; that would unfortunately >> result in an ugly turd at the end of /proc/iomem, but that can be >> addressed if need be, too. > > always enable 64bit resource for 32bit too? > That would address the problem if combined with the "alternative implementation" that I described below, but I'm not sure how well it would go over, especially since the 32-bit x86 world is increasingly getting concentrated on the very-resource-starved end of the computing spectrum. The bottom-line problem is the same: e820, and the e820 allocator, can describe address space that lies outside our real range of possible address space. What to do with that is easy -- it should simply be ignored -- but it does lead to oddball sequencing issues. In that sense, reserving a chunk of address space at the end is cleaner, but that doesn't address the issue of what happens with a 32-bit resource_size_t. Unfortunately, my attempts at reproducing the problem locally has failed so far. -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
