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

[Nicolas Pitre]

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);


Nicolas