Re: [PATCH 1/5] mm: add coherence API for DMA to vmalloc/vmap areas

From: Paul Mundt <lethal@linux-sh.org>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Russell King <rmk@arm.linux.org.uk>,
	Parisc List <linux-parisc@vger.kernel.org>,
	Linux Filesystem Mailing List <linux-fsdevel@vger.kernel.org>,
	linux-arch@vger.kernel.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/5] mm: add coherence API for DMA to vmalloc/vmap areas
Date: Wed, 9 Sep 2009 12:35:32 +0900	[thread overview]
Message-ID: <20090909033532.GD23049@linux-sh.org> (raw)
In-Reply-To: <1252466601.13003.374.camel@mulgrave.site>

On Tue, Sep 08, 2009 at 10:23:21PM -0500, James Bottomley wrote:
> On Wed, 2009-09-09 at 03:17 +0000, James Bottomley wrote:
> > On Virtually Indexed architectures (which don't do automatic alias
> > resolution in their caches), we have to flush via the correct
> > virtual address to prepare pages for DMA.  On some architectures
> > (like arm) we cannot prevent the CPU from doing data movein along
> > the alias (and thus giving stale read data), so we not only have to
> > introduce a flush API to push dirty cache lines out, but also an invalidate
> > API to kill inconsistent cache lines that may have moved in before
> > DMA changed the data
> > 
> > Signed-off-by: James Bottomley <James.Bottomley@suse.de>
> > ---
> >  include/linux/highmem.h |    6 ++++++
> >  1 files changed, 6 insertions(+), 0 deletions(-)
> > 
> > diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> > index 211ff44..9719952 100644
> > --- a/include/linux/highmem.h
> > +++ b/include/linux/highmem.h
> > @@ -17,6 +17,12 @@ static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page
> >  static inline void flush_kernel_dcache_page(struct page *page)
> >  {
> >  }
> > +static incline void flush_kernel_dcache_addr(void *vaddr)
> > +{
> > +}
> > +static incline void invalidate_kernel_dcache_addr(void *vaddr)
> > +{
> > +}
> >  #endif
> 
> OK, so it's been pointed out to me that I didn't compile check this ...
> just testing to see everyone is awake ...
> 
And here I thought it was a new gcc construct along the lines of
inline-if-so-inclined.. :-)