Re: [Xen-devel] [PATCH] xencomm: Remove xencomm

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-03-14 at 10:10 -0400, Boris Ostrovsky wrote:
> On 03/14/2014 03:53 AM, Jan Beulich wrote:
> >>>> On 13.03.14 at 22:55, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> wrote:
> >> Being a feature that has only been used by ia64 and/or ppc it
> >> doesn't seem like we need to keep it any longer in the tree.
> >>
> >> So remove it.
> >>
> >> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> >> ---
> >>   xen/common/Makefile          |    2 -
> >>   xen/common/xencomm.c         |  621 
> >> ------------------------------------------
> >>   xen/include/Makefile         |    1 -
> >>   xen/include/public/xencomm.h |   41 ---
> > Just like noted for the removal of the ia64 bits from the public
> > headers - I'm not sure removing anything from the public headers
> > is ever appropriate. For one, with the implementation going away,
> > the interface definitions don't all of the sudden go away too. If
> > anyone would ever want to resurrect a deleted architecture, still
> > having the old interface definitions in place would point out very
> > clearly what compatibility constraints (with regard to the earlier
> > implementation) to think about.
> 
> If we decide to bring this back the headers will still be available
> in source control.
> 
> >   And second, the building of the
> > unmodified_drivers/ subtree is affected by that removal: IMO
> > there's nothing illegitimate to try to build them against a suitable
> > (older) kernel, yet mkbuildtree taking the public headers from the
> > Xen tree makes it a requirement for the definitions to remain in
> > place.
> 
> But then we would be building drivers against code (OK, just the headers)
> that has not been tested (and more importantly cannot be tested). These
> drivers will never run on this version of Xen so it seems to me they should
> be built against Xen version that they are expected to be running on.

But PV drivers don't "run on Xen", they run against a backend in another
guest. There is absolutely no need to build your drivers for a
particular version of Xen.

(I haven't decided what I think about keeping vs. ditching the
interfaces, so I make no judgement on that aspect)

Ian.


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