On Fri, Mar 19, 2010 at 04:46:54PM +0000, Catalin Marinas wrote: > On Fri, 2010-03-19 at 14:54 +0000, Russell King - ARM Linux wrote: > > On Fri, Mar 19, 2010 at 02:52:00PM +0000, Catalin Marinas wrote: > > > > On Fri, Mar 19, 2010 at 02:41:17PM +0000, Catalin Marinas wrote: > > > > > On Thu, 2010-03-18 at 13:20 +0000, Nicolas Pitre wrote: > > > > > > The only way a highmem page can be unmapped is through kunmap_atomic() > > > > > > where an explicit __cpuc_flush_dcache_area() is performed, or through > > > > > > flush_all_zero_pkmaps() where flush_cache_kmaps() translates into > > > > > > flush_cache_all(). > > > > > > > > > > The thing that I couldn't fully understand with the kunmap_atomic() > > > > > function is that there is a path (when kvaddr < FIXADDR_START) where no > > > > > cache flushing occurs. Can this not happen? > > > > > > > > kunmap interfaces are not for cache flushing; the cache flushing is > > > > only there to ensure consistency when unmapping a mapping on VIVT CPUs. > > > > > > I agree, but then why don't we conditionally call > > > __cpuc_flush_dcache_area() in kunmap_atomic() so that we avoid this > > > flush on non-aliasing VIPT? > > > > Probably because highmem was written at the time for VIVT CPUs. I'm sure > > Nicolas will accept patches to improve performance of highmem for VIPT. > > See below for the VIPT case. But my initial question still remains for > VIVT caches - are all the cases covered? On non-highmem, no cache flushing is expected on kunmap_atomic; it becomes (almost) a no-op. As I've already said, the _only_ reason for flushing the caches in kunmap_atomic() is to ensure consistency when removing the mapping. -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
