On Mon, Jul 09, 2012 at 01:25:23PM +0100, Michal Hocko wrote: > On Wed 04-07-12 15:32:56, Will Deacon wrote: > > When allocating and returning clear huge pages to userspace as a > > response to a fault, we may zero and return a mapping to a previously > > dirtied physical region (for example, it may have been written by > > a private mapping which was freed as a result of an ftruncate on the > > backing file). On architectures with Harvard caches, this can lead to > > I/D inconsistency since the zeroed view may not be visible to the > > instruction stream. > > > > This patch solves the problem by flushing the region after allocating > > and clearing a new huge page. Note that PowerPC avoids this issue by > > performing the flushing in their clear_user_page implementation to keep > > the loader happy, however this is closely tied to the semantics of the > > PG_arch_1 page flag which is architecture-specific. > > > > Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx> > > Signed-off-by: Will Deacon <will.deacon@xxxxxxx> > > --- > > mm/hugetlb.c | 1 + > > 1 files changed, 1 insertions(+), 0 deletions(-) > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index e198831..b83d026 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -2646,6 +2646,7 @@ retry: > > goto out; > > } > > clear_huge_page(page, address, pages_per_huge_page(h)); > > + flush_dcache_page(page); > > __SetPageUptodate(page); > > Does this have to be explicit in the arch independent code? > It seems that ia64 uses flush_dcache_page already in the clear_user_page It would match what is done in similar situations by cow_user_page (mm/memory.c) and shmem_writepage (mm/shmem.c). Other subsystems also have explicit page flushing (DMA bounce, ksm) so I think this is the right place for it. Will -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>