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

[Tim Deegan <tim@xxxxxxx>]

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.

Tim.

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