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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.10.12 at 13:09, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> 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.

Hmm, indeed. But I don't see why, so let me comment there instead.

Jan


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