Re: [PATCH 2/2] x86: replace BIO_VMERGE_BOUNDARY with BIOVEC_PHYS_MERGEABLE

[Jens Axboe <jens.axboe@oracle.com>]

On Mon, Oct 27 2008, FUJITA Tomonori wrote:
> On Mon, 27 Oct 2008 20:18:44 +1100
> Jeremy Fitzhardinge <jeremy@goop.org> wrote:
> 
> > FUJITA Tomonori wrote:
> > > I'm not familiar with what Xen does but why can't Xen just override
> > > BIOVEC_PHYS_MERGEABLE?
> > >
> > > Why does Xen need to hook BIOVEC_PHYS_MERGEABLE to the iommu_bio_merge
> > > parameter (as this patch does)? BIOVEC_PHYS_MERGEABLE and the
> > > iommu_bio_merge parameter are not related at all.
> > >   
> > 
> > No, it doesn't.  It was convenient to reuse that mechanism, but I can 
> > easily re-add something else (which would be more or less identical).
> 
> I still don't see how Xen needs something like the virtual merge
> (sounds that overriding BIOVEC_PHYS_MERGEABLE perfectly works for Xen)
> or why Xen needs a new boot parameter for it. The virtual merge just
> defines how IOMMUs should work.

Pretty much baffles me as well, xen should just need to do

#define BIOVEC_PHYS_MERGEABLE(vec1, vec2)       0

and that should be it.

-- 
Jens Axboe