On Tue, 5 Aug 2014, Kees Cook wrote: > On Fri, May 30, 2014 at 12:25 PM, Nicolas Pitre > <nicolas.pi...@linaro.org> wrote: > > On Fri, 30 May 2014, Rob Herring wrote: > > > >> There's work in flight to support early_ioremap, early console, and RO > >> text patching which all use the fixmap region. > >> > >> There's a couple of options to solve this: > >> > >> - Only support up to 16 cpus. It could be anywhere between 17-31, but > >> that seems somewhat unlikely. Are we really ever going to see 32-bit > >> 32 core systems? > > > > I wouldn't rule that out. I've seen 16-core ARM chips in 2008 (although > > they didn't go into production). Silly limitations like that always > > come back to bite you. And we have better alternatives. > > > >> - Reduce KM_TYPE_NR from 16 to 15. Based on the comment for it, we > >> probably don't want to do that. Is increasing it to the default of 20 > >> worthwhile? Some of the options here would allow doing that. > >> - Add 0xffe00000-0xfff00000 to the fixmap region. This would make > >> fixmap span 2 PMDs with the top PMD having a mixture of uses like we > >> had before. > > > > That would be my preferred approach. Note here it could be > > 0xffe00000-0xfffe0000 to include the whole of the previous fixmap area > > curently unused. > > > >> - push the PCI i/o space down to 0xfec00000 and make fixmap 4MB. This > >> is a cleaner solution as the 2 PMDs are only used for fixmap. This may > >> require some static mapping adjustments on some platforms. > > > > No need. With the latest changes, the fixmap area is between 0xffc00000 > > and 0xffe00000 (there is apparently a mistake in > > Documentation/arm/memory.txt). So currently 0xff000000-0xffc00000 is > > free, which makes the fixmap area far away from the PCI i/o area with > > plenti of space in between. > > So, it seems there is something wrong with this patch series. I had to > revert "ARM: 8031/2: change fixmap mapping region to support 32 CPUs" > to make other fixmap changes work correctly. I think this is due to > the non-highmem config case moving the fixmap to a location where > there is to page table entry...
Could you elaborate please? How can the non-highmem config move the fixmap area? And what are those other fixmap changes? Nicolas -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
