Re: [PATCH v2 for-next 1/2] RDMA/hns: Refactor hns uar mmap flow

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Jun 03, 2021 at 03:37:13PM +0800, Weihang Li wrote:
> From: Xi Wang <wangxi11@huawei.com>
> 
> Classify the uar address by wrapping the uar type and start page as offset
> for hns rdma io mmap.
> 
> Signed-off-by: Xi Wang <wangxi11@huawei.com>
> Signed-off-by: Weihang Li <liweihang@huawei.com>
>  drivers/infiniband/hw/hns/hns_roce_main.c | 27 ++++++++++++++++++++++++---
>  include/uapi/rdma/hns-abi.h               |  4 ++++
>  2 files changed, 28 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/hns/hns_roce_main.c b/drivers/infiniband/hw/hns/hns_roce_main.c
> index 6c6e82b..9610bfd 100644
> +++ b/drivers/infiniband/hw/hns/hns_roce_main.c
> @@ -338,12 +338,23 @@ static void hns_roce_dealloc_ucontext(struct ib_ucontext *ibcontext)
>  	hns_roce_uar_free(to_hr_dev(ibcontext->device), &context->uar);
>  }
>  
> -static int hns_roce_mmap(struct ib_ucontext *context,
> -			 struct vm_area_struct *vma)
> +/* command value is offset[15:8] */
> +static int hns_roce_mmap_get_command(unsigned long offset)
> +{
> +	return (offset >> 8) & 0xff;
> +}
> +
> +/* index value is offset[63:16] | offset[7:0] */
> +static unsigned long hns_roce_mmap_get_index(unsigned long offset)
> +{
> +	return ((offset >> 16) << 8) | (offset & 0xff);
> +}

Please try to avoid using this command stuff copied from mlx drivers,
especially do not encode the qpn in this.

The proper way is to request and return a mmap cookie through the
verb that causes the page to be allocated. For instance specifying a
new input parameter to the create QP udata and an output parameter
with the mmap cookie.

You can look at what the mlx UAR stuff does for some idea how to
convert the old command style to a the preferred cookie style.

Jason