Re: [XenPPC] [rfc] [patch] 64-bitize guest handles

[Hollis Blanchard <hollisb@xxxxxxxxxx>]

On Wed, 2006-06-28 at 06:34 -0400, Jimi Xenidis wrote:
> oops! a typo and an update, see below
> On Jun 27, 2006, at 6:15 PM, Jimi Xenidis wrote:
> > how about:
> >      struct __guest_handle_struct {
> >          char __pad[sizeof (long) - sizeof (void *)];
> needs to be:
>    char __pad[sizeof (u64) - sizeof (void *)];
> 
> Also, we will have to set the __pad member to zero or 32bit  
> "creators" will have garbage there, so let make it an u32:
> 
>    u32 __pad[(sizeof (u64) - sizeof (void *)) / 4];
> 
> and...
> > -#define set_xen_guest_handle(hnd, val)  do { (hnd).p = val; }  
> > while (0)
> > +#define set_xen_guest_handle(hnd, val) \
> > +    do { (hnd).l = (unsigned long)(void *)val; } while (0)
> 
>    #define set_xen_guest_handle(hnd, val) \
>        do { \
>            if (sizeof ((hnd).__pad)) \
>                (hnd).__pad = 0; \
>            (hnd).p = val; \
>        } while (0)

I like the union better than a struct with carefully-constructed
non-overlapping members. Also, the separate assignment to 0 would be
avoided.

-- 
Hollis Blanchard
IBM Linux Technology Center


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