Jan Beulich wrote:
>>>> On 25.03.14 at 18:23,<dgdegra@tycho.nsa.gov>  wrote:
>> >  Event channel arrays are allocated in blocks with EVTCHNS_PER_BUCKET
>> >  elements, which must be a power of 2.  When XSM is disabled, struct
>> >  evtchn is 32 bytes including padding; however, when XSM is enabled, the
>> >  structure becomes larger and EVTCHNS_PER_BUCKET is halved.  Rearranging
>> >  some of the fields in struct evtchn allows a 4-byte XSM field to fit
>> >  within the 32-byte structure.
>> >  
>> >  This rearrangement turns the xen_consumer field of struct evtchn into a
>> >  bitfield and adjusts the xen_consumers array to fit the number of
>> >  addressable elements from this value.  Since there are currently only
>> >  two users of this array, only 3 bits (7 values) are reserved.  This
>> >  field is also used rarely enough that the slight overhead from applying
>> >  a bitmask should not cause problems.
>> >  
>> >  Signed-off-by: Daniel De Graaf<dgdegra@tycho.nsa.gov>
>> >  Cc: David Vrabel<david.vrabel@citrix.com>
>
> Reviewed-by: Jan Beulich<jbeulich@suse.com>

Acked-by: Keir Fraser <keir@xen.org>
>