linux-kernel - Re: [PATCH v3 2/2] SGE buffer and max

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Date:   Wed, 15 Jan 2020 11:57:08 -0800
From:   Rao Shoaib <rao.shoaib@...cle.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     linux-rdma@...r.kernel.org, monis@...lanox.com,
        dledford@...hat.com, sean.hefty@...el.com,
        hal.rosenstock@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] SGE buffer and max_inline data must have same size


On 1/15/20 10:27 AM, Jason Gunthorpe wrote:
> On Mon, Jan 13, 2020 at 04:41:20PM -0800, rao Shoaib wrote:
>> From: Rao Shoaib <rao.shoaib@...cle.com>
>>
>> SGE buffer size and max_inline data should be same. Maximum of the
>> two values requested is used.
>>
>> Signed-off-by: Rao Shoaib <rao.shoaib@...cle.com>
>>   drivers/infiniband/sw/rxe/rxe_qp.c | 23 +++++++++++------------
>>   1 file changed, 11 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/infiniband/sw/rxe/rxe_qp.c b/drivers/infiniband/sw/rxe/rxe_qp.c
>> index aeea994..41c669c 100644
>> +++ b/drivers/infiniband/sw/rxe/rxe_qp.c
>> @@ -235,18 +235,17 @@ static int rxe_qp_init_req(struct rxe_dev *rxe, struct rxe_qp *qp,
>>   		return err;
>>   	qp->sk->sk->sk_user_data = qp;
>>   
>> -	qp->sq.max_wr		= init->cap.max_send_wr;
>> -	qp->sq.max_sge		= init->cap.max_send_sge;
>> -	qp->sq.max_inline	= init->cap.max_inline_data;
>> -
>> -	wqe_size = max_t(int, sizeof(struct rxe_send_wqe) +
>> -			 qp->sq.max_sge * sizeof(struct ib_sge),
>> -			 sizeof(struct rxe_send_wqe) +
>> -			 qp->sq.max_inline);
>> -
>> -	qp->sq.queue = rxe_queue_init(rxe,
>> -				      &qp->sq.max_wr,
>> -				      wqe_size);
>> +	wqe_size = max_t(int, init->cap.max_send_sge * sizeof(struct ib_sge),
>> +			 init->cap.max_inline_data);
>> +	qp->sq.max_sge = wqe_size/sizeof(struct ib_sge);
>> +	qp->sq.max_inline = wqe_size;
>> +
>> +	wqe_size += sizeof(struct rxe_send_wqe);
> Where does this limit the user's request to RXE_MAX_WQE_SIZE ?

My understanding is that the user request can only specify sge's and/or 
inline data. The check for those is made in rxe_qp_chk_cap. Since max 
sge's and max inline data are constrained by RXE_MAX_WQE_SIZE the limit 
is enforced.

>
> I seem to recall the if the requested max can't be satisified then
> that is an EINVAL?
>
> And the init->cap should be updated with the actual allocation.

Since the user request for both (sge's and inline data) has been 
satisfied I decided not to update the values in case the return values 
are being checked. If you prefer that I update the values I can do that.

Shoaib

>
> So more like:
>
>          if (init->cap.max_send_sge > RXE_MAX_SGE ||
>             init->cap.max_inline_data > RXE_MAX_INLINE)
>              return -EINVAL;
>
> 	wqe_size = max_t(int, init->cap.max_sge * sizeof(struct ib_sge),
> 			 init->cap.max_inline_data)
>                     sizeof(struct rxe_send_wqe);
> 	qp->sq.max_sge = init->cap.max_send_sge = wqe_size/sizeof(struct ib_sge);
> 	qp->sq.max_inline = init->cap.max_inline_data = wqe_size;
> 	wqe_size += sizeof(struct rxe_send_wqe);
>
> Jason