Re: [Xen-devel] [PATCH v4 01/12] x86: infrastructure to allow converting certain indirect calls to direct ones

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andrew,

On 02/10/2018 14:21, Andrew Cooper wrote:
> On 02/10/18 11:12, Jan Beulich wrote:
> > --- a/xen/include/xen/lib.h
> > +++ b/xen/include/xen/lib.h
> > @@ -66,6 +66,10 @@
> >   
> >   #define ROUNDUP(x, a) (((x) + (a) - 1) & ~((a) - 1))
> >   
> > +#define count_va_arg_(dot, a1, a2, a3, a4, a5, a6, a7, a8, x, ...) x
> > +#define count_va_arg(args...) \
> > +    count_va_arg_(., ## args, 8, 7, 6, 5, 4, 3, 2, 1, 0)
> This particular bit of review split out for obvious reasons.
>
> We already have __count_args() in the ARM SMCCC infrastructure.  Please
> can we dedup that (broken out into a separate patch) rather than
> introducing a competing version.
>
> The ARM version is buggy.  It is off-by-two in the base case, and
> doesn't compile if fewer than two parameters are passed.  This version
> functions correctly, but should be named with a plural.
The ARM version is *not* buggy. What the ARM version count is the number 
of parameters for the SMCCC function, *not* the number of parameter for 
the call.
This matches the SMCCC where the first parameter is always the function 
ID, the last parameter is always the result structure.
The code will end up to be less readable using a generic count. I am 
planning to Nack anything trying to use a generic count in the SMCCC code.
Cheers,

--
Julien Grall

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