Re: [PATCH rdma-core 10/13] mlx5: Implement the import/unimport MR verbs

[Yishai Hadas <yishaih@dev.mellanox.co.il>]

On 6/19/2020 3:50 PM, Jason Gunthorpe wrote:
> On Wed, Jun 17, 2020 at 10:45:53AM +0300, Yishai Hadas wrote:
>> Implement the import/unimport MR verbs based on their definition as
>> described in the man page.
>>
>> It uses the query MR KABI to retrieve the original MR properties based
>> on its given handle.
>>
>> Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
>>   libibverbs/cmd_mr.c          | 35 +++++++++++++++++++++++++++++++++++
>>   libibverbs/driver.h          |  3 +++
>>   libibverbs/libibverbs.map.in |  1 +
>>   providers/mlx5/mlx5.c        |  2 ++
>>   providers/mlx5/mlx5.h        |  3 +++
>>   providers/mlx5/verbs.c       | 24 ++++++++++++++++++++++++
>>   6 files changed, 68 insertions(+)
>>
>> diff --git a/libibverbs/cmd_mr.c b/libibverbs/cmd_mr.c
>> index cb729b6..6984948 100644
>> +++ b/libibverbs/cmd_mr.c
>> @@ -85,3 +85,38 @@ int ibv_cmd_dereg_mr(struct verbs_mr *vmr)
>>   		return ret;
>>   	return 0;
>>   }
>> +
>> +int ibv_cmd_query_mr(struct ibv_pd *pd, struct verbs_mr *vmr,
>> +		     uint32_t mr_handle)
>> +{
>> +	DECLARE_FBCMD_BUFFER(cmd, UVERBS_OBJECT_MR,
>> +			     UVERBS_METHOD_QUERY_MR,
>> +			     5, NULL);
>> +	struct ibv_mr *mr = &vmr->ibv_mr;
>> +	uint64_t iova;
>> +	int ret;
>> +
>> +	fill_attr_in_obj(cmd, UVERBS_ATTR_QUERY_MR_HANDLE, mr_handle);
>> +	fill_attr_out_ptr(cmd, UVERBS_ATTR_QUERY_MR_RESP_LKEY,
>> +			  &mr->lkey);
>> +	fill_attr_out_ptr(cmd, UVERBS_ATTR_QUERY_MR_RESP_RKEY,
>> +			  &mr->rkey);
>> +	fill_attr_out_ptr(cmd, UVERBS_ATTR_QUERY_MR_RESP_LENGTH,
>> +			  &mr->length);
>> +	/* The iova may be used down the road, let's have it ready from kernel */
>> +	fill_attr_out_ptr(cmd, UVERBS_ATTR_QUERY_MR_RESP_IOVA,
>> +			  &iova);
> 
> There isn't much reason to fill the attribute here..
> 

We have defined this attribute from kernel perspective to be mandatory 
from day one as of other attributes above.
Are you suggesting to change in kernel to let this attribute be optional 
and not fill it here ? other alternative ?

Yishai