[PATCH 0/3] Cache maintenance on VIPT caches

[Nicolas Pitre]

On Tue, 20 Jul 2010, Catalin Marinas wrote:

> On Tue, 2010-07-20 at 18:56 +0900, FUJITA Tomonori wrote:
> > On Fri, 16 Jul 2010 15:39:17 +0100
> > Catalin Marinas <catalin.marinas at arm.com> wrote:
> > > I'm not sure why sg_miter doesn't call flush_dcache_page() but
> > > flush_kernel_dcache_page() (I cc'ed Fujita as he seems to have added
> > > this code).
> > 
> > It is intended to handle D aliasing due to kmap. As cachetlb.txt says
> > that it is assumed here that the user has no incoherent cached copies
> > (it was already addressed elsewhere). So flush_dcache_page() does too
> > much there.
> 
> A related question here - does flush_kernel_dcache_page() need to do
> anything for non-highmem pages? For highmem pages, on ARM, we already
> handle the cache flushing in kunmap().

Well, with your proposed patch we wouldn't anymore.  And semantically we 
shouldn't have to.  Even the fact that kunmap_atomic() does flush the 
cache on VIVT system is an implementation issue not a semantic 
definition (incidentally on VIPT it is not flushed).


Nicolas