Re: [PATCH 4/5] xen: Enforce casting for guest_handle_cast

[Jean Guyader <jean.guyader@citrix.com>]

On 14/06 03:27, Tim Deegan wrote:
> At 15:26 +0100 on 14 Jun (1339687574), Tim Deegan wrote:
> > At 15:08 +0100 on 14 Jun (1339686495), Jean Guyader wrote:
> > > Maybe I should put here the reason that led me to do something
> > > like that. Here is what I'm trying to do:
> > > 
> > >         XEN_GUEST_HANDLE (uint8_t) slop_hnd =
> > >                 guest_handle_cast (pfn_list_hnd, uint8_t);
> > >         guest_handle_add_offset (slop_hnd, sizeof (v4v_pfn_list_t));
> > >         pfn_hnd = guest_handle_cast (slop_hnd, v4v_pfn_t);
> > > 
> > > I need to cast to uint8_t first to get the add_offset to behave
> > > correctly. Maybe what I need would need a new macro that would
> > > do those two operations.
> > > 
> > > What would be the proper way to doing something like this?
> > 
> > You could avoid it altogether by dropping struct v4v_ring_data, and
> > passing a v4v_pfn_t array directly with the 'npage' as a separate
> > hypercall argument.  AFAICS struct v4v_ring_data has no other useful
> > fields.
> 
> Excuse me, I meant struct v4v_pfn_list_t.
> 

You probably mean both, because we doing the same thing with
v4v_ring_data_t and v4v_ring_data_ent_t.

Jean