Re: Re: Re: [PATCH 1/1] Make user mmapped CQ arming flags field 32 bit size to remove 64 bit architecture dependency of siw.

[Jason Gunthorpe <jgg@ziepe.ca>]

On Thu, Aug 08, 2019 at 02:17:57PM +0000, Bernard Metzler wrote:
> 
> >To: "Bernard Metzler" <BMT@zurich.ibm.com>, "Jason Gunthorpe"
> ><jgg@ziepe.ca>
> >From: "Doug Ledford" <dledford@redhat.com>
> >Date: 08/07/2019 08:53PM
> >Cc: linux-rdma@vger.kernel.org
> >Subject: [EXTERNAL] Re: Re: [PATCH 1/1] Make user mmapped CQ arming
> >flags field 32 bit size to remove 64 bit architecture dependency of
> >siw.
> >
> >On Wed, 2019-08-07 at 17:49 +0000, Bernard Metzler wrote:
> >> 
> >> It hurts, but I did finally setup qemu with a ppc image to check,
> >> and so you are right!
> >> 
> >> ...
> >> 
> >> #ifdef __BIG_ENDIAN__
> >> 
> >> seem to be available in both kernel and user land...
> >> 
> >> But, general question: siw in its current shape isn't out
> >> for long, older versions from github are already broken with
> >> the abi. So, silently changing the abi at this stage of siw
> >> deployment is no option? It's a hassle to see an old mistake
> >> carried along forever with that #ifdef statement...no?
> >
> >I was thinking about that myself.
> >
> >This really hasn't been out long enough to completely tie our hands
> >here.  A point update to rdma-core will resolve any user side issues.
> >
> 
> What we are aiming at is ensuring backward compatibility
> for 64bit-BE architectures, which are using siw since this year.
> The community is likely of size zero. 
> I found it hard to find a machine, even in the ppc world, which
> let me test that BE thing. I ended up with an emulator. So I
> assume it is no real world issue to now just change the 64bits 
> flag into 32bits and add a 32bit pad for ABI compliance.

This seems reasonable to me, document all these details in the commit
message.

Jason