Re: Kernel fast memory registration API proposal [RFC]

[Sagi Grimberg <sagig-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

On 7/16/2015 9:08 PM, Jason Gunthorpe wrote:
> On Thu, Jul 16, 2015 at 03:21:04PM +0300, Sagi Grimberg wrote:
>> I gotta say,
>>
>> these suggestions of bool/write or supported_ops with a convert helper
>> seem (to me at least) to make things more complicated.
>>
>> Why not just set the the access_flags as they are?
>> I want local use?
>> set IB_ACCESS_LOCAL_WRITE
>> I want a peer to read from me?
>> set IB_ACCESS_REMOTE_READ
>> I want a peer to write to me?
>> IB_ACCESS_REMOTE_WRITE
>> ...
>>
>> isn't it much simpler?
>
> I don't have a really strong preference, but I like the idea of using
> the OP names because it means the API cannot be used wrong.
>
> Ie this, is absolutely wrong:
>
>   rdma_map_sg_lkey(..,IB_ACCESS_REMOTE_READ);
>
> But this:
>
>   rdma_map_sg_lkey(..,IB_ACCESS_REMOTE_WRITE);
>
> Is only wrong on IB.
>
> While,
>   rdma_map_sg_lkey(..,RDMA_OP_RDMA_READ)
>
> Is always right, and can never be used wrong, and thus is less
> complicated (for the ULP).

I was thinking that the user won't explicitly say which key it registers
and it will be decided from the registration itself.
Meaning, the registration code will do:

if (access | (IB_ACCESS_REMOTE_READ | IB_ACCESS_REMOTE_WRITE)
         register rkey...
else
         register lkey...

Will that work with iWARP? or will this break because
iWARP needs REMOTE_WRITE for lkeys?
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html