Re: [Xen-devel] [PATCH 02/10] xen: make GUEST_HANDLE_64() and uint64_aligned_t available everywhere

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.06.13 at 15:17, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
> On 25/06/13 12:36, Jan Beulich wrote:
>>>>> On 25.06.13 at 11:42, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:
>>>     typedef struct { union { type *p; uint64_t q; }; }          \
>>>         __guest_handle_new_ ## name
>> 
>> The uint64_t here ...
>> 
>>> #undef set_xen_guest_handle_raw
>>> #define set_xen_guest_handle_raw(hnd, val)                  \
>>>     do { if ( sizeof(hnd) == 8 ) *(uint64_t *)&(hnd) = 0;   \
>>>          (hnd).p = val;                                     \
>>>     } while ( 0 )
>>>
>>> #if defined(__XEN__) || (__XEN_TOOLS__)
>>> #define uint64_aligned_t uint64_t __attribute__((aligned(8)))
>>> #define __XEN_GUEST_HANDLE_64(name) __guest_handle_64_ ## name
>>> #define XEN_GUEST_HANDLE_64(name) __XEN_GUEST_HANDLE_64(name)
>>> #endif
>>>
>>> #define __XEN_GUEST_HANDLE_NEW(name) __guest_handle_new_ ## name
>>> /* This must be aligned to 8 bytes with padding if necessary. */
>>> #define XEN_GUEST_HANDLE_NEW(name) __XEN_GUEST_HANDLE_NEW(name)
>> 
>> ... does in no way satisfy the comment here, so what's the point?
> 
> The comment is unclear, sorry.
> 
> /* A structure containing this type of guest handle must align the
>    field to 8 bytes, using padding fields as necessary. */

Okay, now I understand your intention at least. However, I
still don't see a point in doing what you try to do - the consumer
still has to add stuff along with the (oddly named) new handle
type, so why not having it take care of padding _and_ sizing?

Jan


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