Re: [PATCH RFC] xen: arm: Log a warning message when a deprecated hypercall is used

[Ian Campbell <Ian.Campbell@citrix.com>]

On Tue, 2015-01-27 at 11:51 +0000, Ard Biesheuvel wrote:
> On 20 January 2015 at 10:52, Ian Campbell <ian.campbell@citrix.com> wrote:
> > A few folks have been caught out by OSes which call e.g.
> > HYPERVISOR_event_channel_op_compat which has been deprecated since
> > 3.2.2 (i.e. long before Xen on ARM). Existing x86 code can still
> > safely and quietly using those calls, waiting for an unsuspecting ARM
> > porter to turn up and trip over it. This turns out to be rather
> > perplexing when it happens, since it can be obscured e.g. by various
> > conditionals like __XEN_INTERFACE_VERSION__ what is actually being
> > called.
> >
> > Note that I'm making a distinction here between hypercalls which are
> > simply not used/implemented on arm (yet) and those which were
> > deprecated and replaced by a newer variant prior to Xen on ARM even
> > being invented.  The latter will never be implemented on ARM and have
> > non-deprecated aliases leading to confusion so those are the ones for
> > which a warning is useful.
> >
> > Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> > Cc: Jan Beulich <JBeulich@suse.com>
> > Cc: Keir Fraser <keir@xen.org>
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Cc: Anthony PERARD <anthony.perard@citrix.com>
> > ---
> > RFC since I'm not sure how extreme our reaction ought to be here, e.g.
> > I considered domain_crash() or even panic() when in a debug build. A
> > XENLOG_DEBUG message is about the most benign of the options.
> >
> > Jan/Keir, although this is ARM specific I'd welcome your views as
> > x86/REST maintainers.
> >
> > Ard, I've not actually run this -- any chance you could re-b0rk your
> > Tianocore image and give it a go?
> 
> Hello,
> 
> I have been trying not to code against a moving Xen target, so I
> haven't had a go with this yet. Once I go back to testing the GICv3
> support, I will need to rebuild Xen and kernels etc anyway so I will
> give it a try (by the end of the week)

Thanks, no particular hurry, this patch isn't super urgent or anthing.

Ian.