Subject: Re: [PATCH rdma-next 3/3] IB/mlx5: Expose dump and fill memory key

From: Leon Romanovsky <[email-masked]>
Date: Wed, 4 Jul 2018 22:20:15 +0300

On Wed, Jul 04, 2018 at 01:09:37PM -0600, Jason Gunthorpe wrote:
> On Tue, Jun 19, 2018 at 08:47:24AM +0300, Leon Romanovsky wrote:
> > From: Yonatan Cohen <[email-masked]>
> >
> > MLX5 IB HCA offers the memory key, dump_fill_mkey to boost
> > performance, when used in a send or receive operations.
> >
> > It is used to force local HCA operations to skip the PCI bus access,
> > while keeping track of the processed length in the ibv_sge handling.
> >
> > Meaning, instead of a PCI write access the HCA leaves the target
> > memory untouched, and skips filling that packet section. Similar
> > behavior is done upon send, the HCA skips data in memory relevant
> > to this key and saves PCI bus access.
> >
> > This functionality saves PCI read/write operations.
> >
> > Signed-off-by: Yonatan Cohen <[email-masked]>
> > Reviewed-by: Yishai Hadas <[email-masked]>
> > Reviewed-by: Guy Levi <[email-masked]>
> > Signed-off-by: Leon Romanovsky <[email-masked]>
> >  drivers/infiniband/hw/mlx5/main.c | 16 +++++++++++++++-
> >  include/uapi/rdma/mlx5-abi.h      |  3 ++-
> >  2 files changed, 17 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c
> > index c29c7c838980..97113957398d 100644
> > +++ b/drivers/infiniband/hw/mlx5/main.c
> > @@ -1634,6 +1634,7 @@ static struct ib_ucontext *mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
> >  	int err;
> >  	size_t min_req_v2 = offsetof(struct mlx5_ib_alloc_ucontext_req_v2,
> >  				     max_cqe_version);
> > +	u32 dump_fill_mkey;
> >  	bool lib_uar_4k;
> >
> >  	if (!dev->ib_active)
> > @@ -1743,8 +1744,12 @@ static struct ib_ucontext *mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
> >  		}
> >
> >  		err = mlx5_ib_devx_create(dev, context);
> > +	}
> > +
> > +	if (MLX5_CAP_GEN(dev->mdev, dump_fill_mkey)) {
> > +		err = mlx5_cmd_dump_fill_mkey(dev->mdev, &dump_fill_mkey);
> >  		if (err)
> > -			goto out_td;
> > +			goto out_mdev;
> >  	}
>
> Dropping the if (err) after mlx5_ib_devx_create is a rebasing error,
> right?

Sorry, you are right, the fixup is pretty straightforward.

diff --git a/drivers/infiniband/hw/mlx5/main.c
b/drivers/infiniband/hw/mlx5/main.c
index 2bbafee6976c..71f3e9677622 100644
--- a/drivers/infiniband/hw/mlx5/main.c
+++ b/drivers/infiniband/hw/mlx5/main.c
@@ -1739,6 +1739,8 @@ static struct ib_ucontext
*mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
                }

                err = mlx5_ib_devx_create(dev,  context);
                if (err)
 +                       goto out_td;
         }

         if (MLX5_CAP_GEN(dev->mdev, dump_fill_mkey)) {

> Jason