Re: [PATCHv2 1/5] mm: add coherence API for DMA to vmalloc/vmap areas

[Matthew Wilcox <matthew@wil.cx>]

On Thu, Dec 24, 2009 at 10:08:53AM +0000, Matt Fleming wrote:
> On Wed, Dec 23, 2009 at 03:22:21PM -0600, James Bottomley wrote:
> > +
> > +  void flush_kernel_vmap_range(void *vaddr, int size)
> > +       flushes the kernel cache for a given virtual address range in
> > +       the vmap area.  This API makes sure that and data the kernel
> 
>   	      	   	       	   	      	^^^ code and data?

I'd guess it's a typo for 'any data'.

> > +  void invalidate_kernel_vmap_range(void *vaddr, int size)
> > +       invalidates the kernel cache for a given virtual address range
> > +       in the vmap area.  This API is designed to make sure that while
> > +       I/O went on to an address range in the vmap area, the processor
> > +       didn't speculate cache reads and thus make the cache over the
> > +       virtual address stale.
> > +
> 
> Could this sentence be reworked a little? I find the "over the virtual
> address" part a little difficult to parse.

How about:

invalidates the processor cache for a given virtual address range
in the vmap area.  This API addresses the problem that the processor
may have performed speculative reads into its cache of the vmapped
area while I/O was occurring to the underlying physical pages.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."