[RFC 10/11] ARM: arrange for flush_cache_range() to alwaysflush the I-cache

[Russell King - ARM Linux]

On Tue, Nov 24, 2009 at 01:05:56PM +0000, Catalin Marinas wrote:
> On Mon, 2009-11-23 at 20:28 +0000, Russell King - ARM Linux wrote:
> > On Sun, Nov 22, 2009 at 03:28:30PM -0500, Nicolas Pitre wrote:
> > > On Mon, 16 Nov 2009, Russell King - ARM Linux wrote:
> > >
> > > > On Mon, Nov 16, 2009 at 10:46:55AM +0000, Catalin Marinas wrote:
> > > > > > diff --git a/arch/arm/mm/copypage-v6.c b/arch/arm/mm/copypage-v6.c
> > > > > > index 4127a7b..f19ed4e 100644
> > > > > > --- a/arch/arm/mm/copypage-v6.c
> > > > > > +++ b/arch/arm/mm/copypage-v6.c
> > > > > > @@ -41,6 +41,7 @@ static void v6_copy_user_highpage_nonaliasing(struct page *to,
> > > > > >         kfrom = kmap_atomic(from, KM_USER0);
> > > > > >         kto = kmap_atomic(to, KM_USER1);
> > > > > >         copy_page(kto, kfrom);
> > > > > > +       __cpuc_flush_dcache_page(kto);
> > > > > >         kunmap_atomic(kto, KM_USER1);
> > > > > >         kunmap_atomic(kfrom, KM_USER0);
> > > > > >  }
> > > > >
> > > > > Any thoughts one getting this merged (maybe in 2.6.33)? It seems that
> > > > > no-one else has any views on this but the COW text pages problem is
> > > > > still present.
> > > >
> > > > Well, it would be useful to get some comment from Nicolas since
> > > > kunmap_atomic() will call this function for highmem pages.  We might want
> > > > to avoid doing the dcache flush thing multiple times for these, but it
> > > > looks to me like testing PageHighMem(to) leaves us a hole.
> > >
> > > Better test page_address(to) and skip the flush if it is NULL.  That's
> > > what we do elsewhere already.  If page_addressto) is NULL then there is
> > > no long lasting mapping for that page and the cache will be flushed upon
> > > kunmap_atomic().  Hence:
> > >
> > > #ifdef CONFIG_HIGHMEM
> > >       /*
> > >        * kmap_atomic() doesn't set the page virtual address, and
> > >        * kunmap_atomic() takes care of cache flushing already.
> > >        */
> > >       if (page_address(to) != NULL)
> > > #endif
> > >               __cpuc_flush_dcache_page(kto);
> > 
> > Okay, can we get this combined with Catalin's patch and applied to all
> > applicable processors (which I assume would be just v6 and v7) ?
> 
> I'm ok with this.

Sorry, I wasn't clear enough.  I was expecting you to update your patch,
and once the other copy_user_page stuff finally gets the "yes it solves
the problem" response from Steven, it can be committed and merged into
this branch.