>
> On Thu, May 17, 2018 at 11:18:28AM +0530, Raju Rangoju wrote:
> >
> > + /* The support for new kernel mode SRQ extends the t4_cqe struct
> > + * size to 64 Bytes from existing 32 Bytes. But, this change brings
> > + * in the library/kernel ABI and 32/64 Byte CQE compatibility
issues.
> > + *
> > + * To address these issues, the user <-> kernel response message
> > + * c4iw_create_cq_resp's 'reserved' field has been renamed to
'flags'.
> > + *
> > + * Newer version of libcxgb4 can pre-initialize the 'flags' field in
> > + * the request struct with the flag C4IW_64B_CQE. And a new
> iw_cxgb4
> > + * can detect the new libcxgb4 by checking for the C4IW_64B_CQE
> flag
> > + * in the structure c4iw_create_cq received from userspace.
> > + * New kernel driver can not work with older userspace library,
> > + * c4iw_create_cq() will log a warning message to upgrade libcxgb4
> and
> > + * aborts the cq creation in this case.
> > + *
> > + * Likewise, new iw_cxgb4 which supports 64B CQE will set the flag
> > + * C4IW_64B_CQE in c4iw_create_cq_resp struct. So, if the response
> > + * from the create_cq verb results in the flags field still being
zero,
> > + * libcxgb4 can destroy the cq and print a warning and fail the user
> > + * create cq verb.
> > + */
> > +
> > + if (ib_context && udata->inlen < sizeof(ucmd)) {
> > + pr_err_once("WARNING: Downlevel libcxgb4. RDMA cannot
> be supported with this driver/lib combination. Please update
libcxgb4.\n");
> > + return ERR_PTR(-EINVAL);
> > + }
>
> Nope, hard NAK on this idea.
>
> The driver must continue to support current user space with full
> compatibility.
>
> And user space must generally support all past kernels as well.
>
> Jason
Hey Raju, please separate this cqe issue into its own patch series for both
kernel and rdma-core. It will simplify reviewing and testing 32/64
support.
Thanks!
Steve.
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