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

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

On Tue, 2015-01-20 at 11:05 +0000, Jan Beulich wrote:
> >>> On 20.01.15 at 11:52, <ian.campbell@citrix.com> wrote:
> > 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.
> 
> And I think it shouldn't be more than that in the first round. We
> may want to consider logging a message on x86 too, but of
> course only optionally depending on a command line option.

OK.

> > --- a/xen/arch/arm/traps.c
> > +++ b/xen/arch/arm/traps.c
> > @@ -1148,6 +1148,22 @@ die:
> >  }
> >  #endif
> >  
> > +static register_t do_deprecated_hypercall(void)
> > +{
> > +    struct cpu_user_regs *regs = guest_cpu_user_regs();
> > +    const register_t op =
> > +#ifdef CONFIG_ARM_64
> > +        !is_32bit_domain(current->domain) ?
> > +            regs->x16
> > +        :
> > +#endif
> > +            regs->r12;
> > +
> > +    gdprintk(XENLOG_DEBUG, "%pv: deprecated hypercall %ld\n",
> > +             current, (unsigned long)op);
> 
> If this was x86 code, I'd complain about the cast...

The correct format code is PRIregister (since register_t can be 32- or
64-bit for arm32 vs arm64 respectively), but it is in hex and xen.h
lists __HYPERVISOR_* in decimal so that's what I wanted to print for
each of manually looking.

> > @@ -1167,15 +1183,29 @@ typedef struct {
> >          .fn = (arm_hypercall_fn_t) &do_arm_ ## _name,                \
> >          .nr_args = _nr_args,                                         \
> >      }
> > +/*
> > + * Only use this for hypercalls which were deprecated (i.e. replaced
> > + * by something else) before Xen on ARM was created, i.e. *not* for
> > + * hypercalls which are simply not yet used on ARM.
> > + */
> > +#define HYPERCALL_DEPRECATED(_name, _nr_args)                   \
> > +    [ __HYPERVISOR_##_name ] = {                                \
> > +        .fn = (arm_hypercall_fn_t) &do_deprecated_hypercall,    \
> 
> ... and the redundant &.

It's consistent with the other variants of this macro.

Ian.