Re: [Xen-devel] [PATCH 19/21] xen: introduce XEN_GUEST_HANDLE_PARAM

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-10-05 at 12:05 +0100, Jan Beulich wrote:
> >>> On 05.10.12 at 12:38, Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
> > From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > 
> > XEN_GUEST_HANDLE_PARAM is going to be used to distinguish guest pointers
> > stored in memory from guest pointers as hypercall parameters.
> > 
> > guest_handle_* macros default to XEN_GUEST_HANDLE_PARAM as return type.
> > Two new guest_handle_to_param and guest_handle_from_param macros are
> > introduced to do conversions.
> > 
> > Changes in v2:
> > 
> > - add 2 missing #define _XEN_GUEST_HANDLE_PARAM for the compilation of
> > the compat code.
> > 
> > Changes in v3:
> > 
> > - move the guest_handle_cast change into this patch;
> > - add a clear comment on top of guest_handle_cast;
> > - also s/XEN_GUEST_HANDLE/XEN_GUEST_HANDLE_PARAM in
> >   guest_handle_from_ptr and const_guest_handle_from_ptr;
> > - introduce guest_handle_from_param and guest_handle_to_param.
> 
> I may have asked this before, but don't recall the answer: Is there
> really a use case for conversions in both directions? I would think
> that only the "to" version is really useful...

I can see uses of both in the patched tree. e.g. the from case is used
in handle_iomem_range on x86.

Ian.



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