Re: [PATCH v3 3/6] RDMA/rxe: Create AH index and return to user space

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Jul 22, 2021 at 04:22:42PM -0500, Bob Pearson wrote:
> Make changes to rdma_user_rxe.h to allow indexing AH objects, passing
> the index in UD send WRs to the driver and returning the index to the rxe
> provider.
> 
> Modify rxe_create_ah() to add an index to AH when created and if
> called from a new user provider return it to user space. If called
> from an old provider mark the AH as not having a useful index.
> Modify rxe_destroy_ah to drop the index before deleting the object.
> 
> Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
>  drivers/infiniband/sw/rxe/rxe_verbs.c | 31 ++++++++++++++++++++++++++-
>  drivers/infiniband/sw/rxe/rxe_verbs.h |  2 ++
>  include/uapi/rdma/rdma_user_rxe.h     |  8 ++++++-
>  3 files changed, 39 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
> index 725015a2e84c..7181e21f0c55 100644
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
> @@ -161,9 +161,19 @@ static int rxe_create_ah(struct ib_ah *ibah,
>  			 struct ib_udata *udata)
>  
>  {
> -	int err;
>  	struct rxe_dev *rxe = to_rdev(ibah->device);
>  	struct rxe_ah *ah = to_rah(ibah);
> +	struct rxe_create_ah_resp __user *uresp = NULL;
> +	int err;
> +
> +	if (udata) {
> +		/* test if new user provider */
> +		if (udata->outlen >= sizeof(*uresp))
> +			uresp = udata->outbuf;
> +		ah->is_user = true;
> +	} else {
> +		ah->is_user = false;
> +	}
>  
>  	err = rxe_av_chk_attr(rxe, init_attr->ah_attr);
>  	if (err)
> @@ -173,6 +183,24 @@ static int rxe_create_ah(struct ib_ah *ibah,
>  	if (err)
>  		return err;
>  
> +	/* create index > 0 */
> +	rxe_add_index(ah);
> +	ah->ah_num = ah->pelem.index;
> +
> +	if (uresp) {
> +		/* only if new user provider */
> +		err = copy_to_user(&uresp->ah_num, &ah->ah_num,
> +					 sizeof(uresp->ah_num));

This should just a using a min_t(size_t udata->outlen, sizeof(*uresp))

And this needs to create the uresp on the stack and copy the whole
thing, not try to copy single values at a time

> diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.h b/drivers/infiniband/sw/rxe/rxe_verbs.h
> index 959a3260fcab..500c47d84500 100644
> +++ b/drivers/infiniband/sw/rxe/rxe_verbs.h
> @@ -48,6 +48,8 @@ struct rxe_ah {
>  	struct rxe_pool_entry	pelem;
>  	struct rxe_pd		*pd;
>  	struct rxe_av		av;
> +	bool			is_user;
> +	int			ah_num;

unsigned int?

Jason