Re: [PATCH v3 rdma-next 2/2] RDMA/qedr: Add EDPM max size to alloc ucontext response

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Jul 07, 2020 at 09:31:00AM +0300, Michal Kalderon wrote:
> User space should receive the maximum edpm size from kernel
> driver, similar to other edpm/ldpm related limits.
> Add an additional parameter to the alloc_ucontext_resp
> structure for the edpm maximum size.
> 
> In addition, pass an indication from user-space to kernel
> (and not just kernel to user) that the DPM sizes are supported.
> 
> This is for supporting backward-forward compatibility between driver and
> lib for everything related to DPM transaction and limit sizes.
> 
> This should have been part of commit mentioned in Fixes tag.
> Fixes: 93a3d05f9d68 ("RDMA/qedr: Add kernel capability flags for dpm
> enabled mode")
> Signed-off-by: Ariel Elior <ariel.elior@marvell.com>
> Signed-off-by: Michal Kalderon <michal.kalderon@marvell.com>
>  drivers/infiniband/hw/qedr/verbs.c | 9 ++++++---
>  include/uapi/rdma/qedr-abi.h       | 6 +++++-
>  2 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/qedr/verbs.c b/drivers/infiniband/hw/qedr/verbs.c
> index fbb0c66c7f2c..cfe4cd637f1c 100644
> +++ b/drivers/infiniband/hw/qedr/verbs.c
> @@ -320,9 +320,12 @@ int qedr_alloc_ucontext(struct ib_ucontext *uctx, struct ib_udata *udata)
>  				  QEDR_DPM_TYPE_ROCE_LEGACY |
>  				  QEDR_DPM_TYPE_ROCE_EDPM_MODE;
>  
> -	uresp.dpm_flags |= QEDR_DPM_SIZES_SET;
> -	uresp.ldpm_limit_size = QEDR_LDPM_MAX_SIZE;
> -	uresp.edpm_trans_size = QEDR_EDPM_TRANS_SIZE;
> +	if (ureq.context_flags & QEDR_SUPPORT_DPM_SIZES) {

Why does this need an input flag just to set some outputs?

The usual truncate on not enough size should take care of it, right?

Jason