Re: [PATCH v6 2/4] xen/arm: use SYMBOL when required

[Stefano Stabellini <sstabellini@kernel.org>]

On Fri, 11 Jan 2019, Jan Beulich wrote:
> >> > --- a/xen/arch/arm/setup.c
> >> > +++ b/xen/arch/arm/setup.c
> >> > @@ -772,8 +772,10 @@ void __init start_xen(unsigned long boot_phys_offset,
> >> >  
> >> >      /* Register Xen's load address as a boot module. */
> >> >      xen_bootmodule = add_boot_module(BOOTMOD_XEN,
> >> > -                             (paddr_t)(uintptr_t)(_start + boot_phys_offset),
> >> > -                             (paddr_t)(uintptr_t)(_end - _start + 1), false);
> >> > +                             (paddr_t)(uintptr_t)(SYMBOL(_start) +
> >> > +                                                  boot_phys_offset),
> >> > +                             (paddr_t)(uintptr_t)(SYMBOL(_end) -
> >> > +                                                  SYMBOL(_start) + 1), false);
> >> 
> >> Why you need the double casts, i.e. why does (uintptr_t) alone not
> >> suffice?
> > 
> > The original reason was just not to change the existing code outside of
> > adding SYMBOL :-)
> > 
> > But to answer your question, uintptr_t is the same size of char*, while
> > paddr_t is always 64bit. uintptr_t casts to integer type, paddr_t casts
> > to the right size. I don't think it is allowed to change from pointer to
> > integer and change integer size in a single cast.
> 
> Correct, but that's not what I've been asking for. Instead I'd like
> to see the (paddr_t) casts dropped, at least if this was in code I'm
> the maintainer for.

But add_boot_module takes paddr_t as arguments. Why would you want the
explicit cast dropped? Just to rely on the implicit cast? This way is
clearer, but either way is fine by me BTW.

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