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

[Russell King - ARM Linux]

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) ?

Catalin?