-----"Jason Gunthorpe" <jgg@xxxxxxxx> wrote: -----
>To: "Bernard Metzler" <BMT@xxxxxxxxxxxxxx>
>From: "Jason Gunthorpe" <jgg@xxxxxxxx>
>Date: 08/06/2019 05:31PM
>Cc: linux-rdma@xxxxxxxxxxxxxxx
>Subject: Re: Re: [PATCH 1/1] Make user mmapped CQ arming flags field
>32 bit size to remove 64 bit architecture dependency of siw.
>
>On Tue, Aug 06, 2019 at 02:53:49PM +0000, Bernard Metzler wrote:
>
>> >> index 7de68f1dc707..af735f55b291 100644
>> >> +++ b/include/uapi/rdma/siw-abi.h
>> >> @@ -180,6 +180,7 @@ struct siw_cqe {
>> >> * to control CQ arming.
>> >> */
>> >> struct siw_cq_ctrl {
>> >> - __aligned_u64 notify;
>> >> + __u32 flags;
>> >> + __u32 pad;
>> >
>> >The commit message needs to explain why this is compatible with
>> >existing user space, if it is even is safe..
>> >
>> Old libsiw would remain compatible with the new layout, since it
>> simply reads the 32bit 'flags' and zeroed 32bit 'pad' into a 64bit
>> 'notify', ending with reading the same bits.
>
>Even on big endian?
>
Well I do not have access to a BE system right now to verify.
But on a BE system, the lowest 3 bits (which are in use) of the first
32bit variable 'flags' shall be the lowest (leftmost) 3 bits of an
'overlayed' 64bit variable 'notify' as well...
