On Wed, 2006-06-28 at 15:02 -0400, Jimi Xenidis wrote:
> On Jun 28, 2006, at 1:10 PM, Hollis Blanchard wrote:
>
> > On Wed, 2006-06-28 at 06:34 -0400, Jimi Xenidis wrote:
> >>
> >> #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.
>
> hmm, really! Ok, then you will have to also fix:
> #define get_xen_guest_handle(val, hnd) do { val = (hnd).p; }
> while (0)
>
> or the 32bit caller will only get the high-order 32bit into val.
Oh, yeah. I remember getting that wrong last time this came up, too.
> > Also, the separate assignment to 0 would be avoided.
>
> In 32 bits the store in of a long long is still 2 stw instructions,
> and the conditional will get optimized away so the instruction
> sequence is equivalent.
>
> I'll leave it to you.
OK, I guess I'll just go with the struct hackery (though I think it's
ugly as hell :) .
Of course, before committing I was hoping to find out from you if it
helps with the memory_reservation problem you were having. Does it?
--
Hollis Blanchard
IBM Linux Technology Center
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