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

[Julien Grall <julien.grall@xxxxxxx>]

On 02/10/2018 14:35, Andrew Cooper wrote:
> On 02/10/18 14:28, Julien Grall wrote:
> > 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.
> Yes it is buggy, because it doesn't behave as the name suggests.
>
> If you mean the infrastructure to have SMCCC specific behaviour, the
> macros should be named suitably, to avoid interfering with common code.
Well the code is coming from Linux. Feel free to send a patch to fix the 
name in Linux and Xen.
Cheers,

--
Julien Grall

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