Hi Helge, On Sun, Nov 17, 2013 at 10:23:08PM +0100, Helge Deller wrote: > On 11/16/2013 09:09 PM, Benjamin LaHaise wrote: > > On Sat, Nov 16, 2013 at 09:07:18PM +0100, Simon Baatz wrote: > >> On Fri, Nov 15, 2013 at 02:42:05PM -0800, James Bottomley wrote: > >>> On Fri, 2013-11-15 at 23:05 +0100, Helge Deller wrote: > >>>> When a user page mapping is released via kunmap*() functions, the D-cache needs > >>>> to be flushed via flush_dcache_page() to avoid D-cache aliasing issues. > >>>> > >>>> This patch fixes aio on the parisc platform (and probably others). > >>> > >>> This should be flush_kernel_dcache_page(). flush_dcache_page() is for > >>> full coherency but for unmap, we know the page was coherent going in and > >>> may have been modified by the kernel, so only the kernel view needs to > >>> be sync'd. Technically, by the kernel API, the flush should be done > >>> *before* unmapping. This would have mattered on parisc until we did > >>> flush via tmpalias which means we no-longer care if the mapping for the > >>> flush exists or not because we always recreate it via the tmpalias > >>> pages. > >> > >> On ARM, flush_kernel_dcache_page() actually assumes that the page is > >> mapped. It avoids double flushing of highmem pages by not flushing > >> in those cases where kunmap_atomic() already takes care of flushing. > > > > Helge -- are you going to resubmit a version of this patch that makes the > > recommended change? > > Sure, I'll do. May need some time for testing the various machine types though. > Maybe in the end you can drop my patch since we might be able to fix it in the > parisc arch code. Could you provide me with the test case(s) you are running to reproduce the problem? I could test this on aliasing D-cache on ARM as well. Since kmap/kunmap do not flush in general on ARM, we might need the explicit flushes here. - Simon -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
