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

Hal Rosenstock
2019-08-19T13:40:28Z

On 8/19/2019 8:21 AM, Jason Gunthorpe wrote:
> 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?

include/rdma/ib_cm.h:#define IB_SERVICE_ID_AGN_MASK
cpu_to_be64(0xFF00000000000000ULL)

IB_SERVICE_ID_AGN_MASK masks entire first byte of OUI which seems like
too much to me as it contains company related bits.

Would it work just masking the first 2 bits (local/global and X bits) ?

-- Hal

> Jason
>