Re: [PATCH] RDMA/srpt: Filter out AGN bits

[Jason Gunthorpe <jgg@mellanox.com>]

On Wed, Aug 14, 2019 at 08:15:07AM -0700, Bart Van Assche wrote:
> The ib_srpt driver derives its default service GUID from the node GUID
> of the first encountered HCA. Since that service GUID is passed to
> ib_cm_listen(), the AGN bits must not be set. Since the AGN bits can
> be set in the node GUID of RoCE HCAs, filter these bits out. This
> patch avoids that loading the ib_srpt driver fails as follows for the
> hns driver:
> 
>   ib_srpt srpt_add_one(hns_0) failed.
> 
> Cc: oulijun <oulijun@huawei.com>
> Reported-by: oulijun <oulijun@huawei.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
>  drivers/infiniband/ulp/srpt/ib_srpt.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.c b/drivers/infiniband/ulp/srpt/ib_srpt.c
> index e25c70a56be6..114bf8d6c82b 100644
> +++ b/drivers/infiniband/ulp/srpt/ib_srpt.c
> @@ -3109,7 +3109,8 @@ static void srpt_add_one(struct ib_device *device)
>  	srpt_use_srq(sdev, sdev->port[0].port_attrib.use_srq);
>  
>  	if (!srpt_service_guid)
> -		srpt_service_guid = be64_to_cpu(device->node_guid);
> +		srpt_service_guid = be64_to_cpu(device->node_guid) &
> +			~IB_SERVICE_ID_AGN_MASK;

This seems kind of sketchy, masking bits in the GUID is going to make
it non-unique.. Should we do this only for roce or something?

Hal, do you have any insight?

Jason