[ofa-general] Re: IB/core: Add creation flags to struct ib_qp_init_attr

[Or Gerlitz]

Roland Dreier wrote:
> Subject: [PATCH] IB/core: Add creation flags to struct ib_qp_init_attr
>
> Add a create_flags member to struct ib_qp_init_attr that will allow a
> kernel verbs consumer to create a pass special flags when creating a QP.
> Add a flag value for telling low-level drivers that a QP will be used
> for IPoIB UD LSO.  The create_flags member will also be useful for XRC
> and ehca low-latency QP support.
Roland, can you please comment what is the approach you prefer to see 
for --user space-- implementation of features such as the ehca low 
latency and the mlx4 block loopback QP "types"? do you want to go the 
XRC way of not breaking the ABI by introducing a new create-qp verb per 
feature as Jack said they did:
> I got around the create_flags problem by adding a new verb to userspace
> (ibv_create_xrc_rcv_qp() ) with its own ABI to kernel space.  Since the kernel-space
> function (added to uverbs_cmd: ib_uverbs_create_xrc_rcv_qp() ) "knew" that it 
> was creating an XRC_RCV qp, it set the flag in ib_qp_init_attr appropriately.
If this is what you prefer to see, does it makes sense to have one new 
verb that can be used for xrc, ehca-ll, mlx4-block loopback and what 
ever new features we want to add for user space QPs in the future?

Or.