linux-kernel - Re: [PATCH for-next v5 7/7] RDMA/rxe: Add support for the traditional Atomic operations with ODP

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Message-ID: <edad669f-e84e-a9ba-9554-87ae1d571931@gmail.com>
Date:   Mon, 22 May 2023 13:49:31 -0500
From:   Bob Pearson <rpearsonhpe@...il.com>
To:     Daisuke Matsuda <matsuda-daisuke@...itsu.com>,
        linux-rdma@...r.kernel.org, leonro@...dia.com, jgg@...dia.com,
        zyjzyj2000@...il.com
Cc:     linux-kernel@...r.kernel.org, yangx.jy@...itsu.com,
        lizhijian@...itsu.com, y-goto@...itsu.com
Subject: Re: [PATCH for-next v5 7/7] RDMA/rxe: Add support for the traditional
 Atomic operations with ODP

On 5/18/23 03:21, Daisuke Matsuda wrote:
> Enable 'fetch and add' and 'compare and swap' operations to manipulate
> data in an ODP-enabled MR. This is comprised of the following steps:
>  1. Check the driver page table(umem_odp->dma_list) to see if the target
>     page is both readable and writable.
>  2. If not, then trigger page fault to map the page.
>  3. Update the entry in the MR xarray.
>  4. Execute the operation.
> 
> umem_mutex is used to ensure that dma_list (an array of addresses of an MR)
> is not changed while it is being checked and that the target page is not
> invalidated before data access completes.
> 
> Signed-off-by: Daisuke Matsuda <matsuda-daisuke@...itsu.com>
> ---
>  drivers/infiniband/sw/rxe/rxe.c      |  1 +
>  drivers/infiniband/sw/rxe/rxe_loc.h  |  9 +++++++++
>  drivers/infiniband/sw/rxe/rxe_odp.c  | 26 ++++++++++++++++++++++++++
>  drivers/infiniband/sw/rxe/rxe_resp.c |  5 ++++-
>  4 files changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/sw/rxe/rxe.c b/drivers/infiniband/sw/rxe/rxe.c
> index 207a022156f0..abd3267c2873 100644
> --- a/drivers/infiniband/sw/rxe/rxe.c
> +++ b/drivers/infiniband/sw/rxe/rxe.c
> @@ -88,6 +88,7 @@ static void rxe_init_device_param(struct rxe_dev *rxe)
>  		rxe->attr.odp_caps.per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_RECV;
>  		rxe->attr.odp_caps.per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_WRITE;
>  		rxe->attr.odp_caps.per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_READ;
> +		rxe->attr.odp_caps.per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_ATOMIC;
>  		rxe->attr.odp_caps.per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_SRQ_RECV;
>  	}
>  }
> diff --git a/drivers/infiniband/sw/rxe/rxe_loc.h b/drivers/infiniband/sw/rxe/rxe_loc.h
> index 4b95c8c46bdc..b9d2985774ee 100644
> --- a/drivers/infiniband/sw/rxe/rxe_loc.h
> +++ b/drivers/infiniband/sw/rxe/rxe_loc.h
> @@ -208,6 +208,9 @@ int rxe_odp_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length,
>  			 u64 iova, int access_flags, struct rxe_mr *mr);
>  int rxe_odp_mr_copy(struct rxe_mr *mr, u64 iova, void *addr, int length,
>  		    enum rxe_mr_copy_dir dir);
> +int rxe_odp_mr_atomic_op(struct rxe_mr *mr, u64 iova, int opcode,
> +			 u64 compare, u64 swap_add, u64 *orig_val);
> +
>  #else /* CONFIG_INFINIBAND_ON_DEMAND_PAGING */
>  static inline int
>  rxe_odp_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length, u64 iova,
> @@ -221,6 +224,12 @@ rxe_odp_mr_copy(struct rxe_mr *mr, u64 iova, void *addr,
>  {
>  	return -EOPNOTSUPP;
>  }
> +static inline int
> +rxe_odp_mr_atomic_op(struct rxe_mr *mr, u64 iova, int opcode,
> +		     u64 compare, u64 swap_add, u64 *orig_val)
> +{
> +	return RESPST_ERR_UNSUPPORTED_OPCODE;
> +}
>  
>  #endif /* CONFIG_INFINIBAND_ON_DEMAND_PAGING */
>  
> diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c
> index cbe5d0c3fcc4..194b1fab98b7 100644
> --- a/drivers/infiniband/sw/rxe/rxe_odp.c
> +++ b/drivers/infiniband/sw/rxe/rxe_odp.c
> @@ -283,3 +283,29 @@ int rxe_odp_mr_copy(struct rxe_mr *mr, u64 iova, void *addr, int length,
>  
>  	return err;
>  }
> +
> +int rxe_odp_mr_atomic_op(struct rxe_mr *mr, u64 iova, int opcode,
> +			 u64 compare, u64 swap_add, u64 *orig_val)
> +{
> +	int err;
> +	struct ib_umem_odp *umem_odp = to_ib_umem_odp(mr->umem);
> +
> +	/* If pagefault is not required, umem mutex will be held until the
> +	 * atomic operation completes. Otherwise, it is released and locked
> +	 * again in rxe_odp_map_range() to let invalidation handler do its
> +	 * work meanwhile.
> +	 */
> +	mutex_lock(&umem_odp->umem_mutex);
> +
> +	/* Atomic operations manipulate a single char. */
> +	err = rxe_odp_map_range(mr, iova, sizeof(char), 0);
> +	if (err)
> +		return err;
> +
> +	err = rxe_mr_do_atomic_op(mr, iova, opcode, compare,
> +				  swap_add, orig_val);
> +
> +	mutex_unlock(&umem_odp->umem_mutex);
> +
> +	return err;
> +}
> diff --git a/drivers/infiniband/sw/rxe/rxe_resp.c b/drivers/infiniband/sw/rxe/rxe_resp.c
> index 90c31c4f2944..0a918145dc07 100644
> --- a/drivers/infiniband/sw/rxe/rxe_resp.c
> +++ b/drivers/infiniband/sw/rxe/rxe_resp.c
> @@ -684,7 +684,10 @@ static enum resp_states atomic_reply(struct rxe_qp *qp,
>  		u64 iova = qp->resp.va + qp->resp.offset;
>  
>  		if (mr->odp_enabled)
> -			err = RESPST_ERR_UNSUPPORTED_OPCODE;
> +			err = rxe_odp_mr_atomic_op(mr, iova, pkt->opcode,
> +						   atmeth_comp(pkt),
> +						   atmeth_swap_add(pkt),
> +						   &res->atomic.orig_val);
>  		else
>  			err = rxe_mr_do_atomic_op(mr, iova, pkt->opcode,
>  						  atmeth_comp(pkt),

Reviewed-by: Bob Pearson <rpearsonhpe@...il.com>