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SubjectRE: [RFC PATCH rdma-next 00/10] RDMA/rxe: Add RDMA FLUSH operation
Date
1)
> rdma_post_flush(struct rdma_cm_id *id, void *context, struct ibv_sge *sgl,
> int nsge, int flags, uint32_t type, uint32_t level,
> uint64_t remote_addr, uint32_t rkey)
Shall we not use struct ibv_sge *sgl in this API call but explicitly use flush length (DMALen) argument?
It will be similar to other rdma_post_XXX API calls where ibv_sge is not used at all.
Ibv_sge is used only in rdma_post_XXXv API calls.

2)
>struct ibv_send_wr {
>...
> union {
> struct {
> uint64_t remote_addr;
> uint32_t rkey;
> uint32_t type;
> uint32_t level;
> } flush;

Shall we extend this structure with
uint32_t length
and abandon using *sg_list as it is related in RDMA verbs to local memory access only:

Ibv_post_send.3:
struct ibv_sge *sg_list; /* Pointer to the s/g array */
int num_sge; /* Size of the s/g array */

In the case of flush, there is no local context at all.

Thanks
Tomasz

> -----Original Message-----
> From: Li Zhijian <lizhijian@cn.fujitsu.com>
> Sent: Tuesday, December 28, 2021 9:07 AM
> To: linux-rdma@vger.kernel.org; zyjzyj2000@gmail.com; jgg@ziepe.ca;
> aharonl@nvidia.com; leon@kernel.org
> Cc: linux-kernel@vger.kernel.org; mbloch@nvidia.com;
> liweihang@huawei.com; liangwenpeng@huawei.com;
> yangx.jy@cn.fujitsu.com; rpearsonhpe@gmail.com; y-goto@fujitsu.com; Li
> Zhijian <lizhijian@cn.fujitsu.com>
> Subject: [RFC PATCH rdma-next 00/10] RDMA/rxe: Add RDMA FLUSH
> operation
>
> Hey folks,
>
> These patches are going to implement a *NEW* RDMA opcode "RDMA
> FLUSH".
> In IB SPEC 1.5[1][2], 2 new opcodes, ATOMIC WRITE and RDMA FLUSH were
> added in the MEMORY PLACEMENT EXTENSIONS section.
>
> FLUSH is used by the requesting node to achieve guarantees on the data
> placement within the memory subsystem of preceding accesses to a single
> memory region, such as those performed by RDMA WRITE, Atomics and
> ATOMIC WRITE requests.
>
> The operation indicates the virtual address space of a destination node and
> where the guarantees should apply. This range must be contiguous in the
> virtual space of the memory key but it is not necessarily a contiguous range
> of physical memory.
>
> FLUSH packets carry FLUSH extended transport header (see below) to
> specify the placement type and the selectivity level of the operation and
> RDMA extended header (RETH, see base document RETH definition) to
> specify the R_Key VA and Length associated with this request following the
> BTH in RC, RDETH in RD and XRCETH in XRC.
>
> RC FLUSH:
> +----+------+------+
> |BTH | FETH | RETH |
> +----+------+------+
>
> RD FLUSH:
> +----+------+------+------+
> |BTH | RDETH| FETH | RETH |
> +----+------+------+------+
>
> XRC FLUSH:
> +----+-------+------+------+
> |BTH | XRCETH| FETH | RETH |
> +----+-------+------+------+
>
> Currently, we introduce RC and RD services only, since XRC has not been
> implemented by rxe yet.
> NOTE: only RC service is tested now, and since other HCAs have not
> added/implemented FLUSH yet, we can only test FLUSH operation in both
> SoftRoCE/rxe devices.
>
> The corresponding rdma-core and FLUSH example are available on:
> https://github.com/zhijianli88/rdma-core/tree/rfc
>
> Below list some details about FLUSH transport packet:
>
> A FLUSH message is built upon FLUSH request packet and is responded
> successfully by RDMA READ response of zero size.
>
> oA19-2: FLUSH shall be single packet message and shall have no payload.
>
> oA19-2: FLUSH shall be single packet message and shall have no payload.
> oA19-5: FLUSH BTH shall hold the Opcode = 0x1C
>
> FLUSH Extended Transport Header(FETH)
> +-----+-----------+------------------------+----------------------+
> |Bits | 31-6 | 5-4 | 3-0 |
> +-----+-----------+------------------------+----------------------+
> | | Reserved | Selectivity Level(SEL) | Placement Type(PLT) |
> +-----+-----------+------------------------+----------------------+
>
> Selectivity Level (SEL) – defines the memory region scope the FLUSH should
> apply on. Values are as follows:
> • b’00 - Memory Region Range: FLUSH applies for all preceding memory
> updates to the RETH range on this QP. All RETH fields shall be
> valid in this selectivity mode. RETH:DMALen field shall be
> between zero and (2 31 -1) bytes (inclusive).
> • b’01 - Memory Region: FLUSH applies for all preceding memory up-
> dates to RETH.R_key on this QP. RETH:DMALen and RETH:VA
> shall be ignored in this mode.
> • b'10 - Reserved.
> • b'11 - Reserved.
>
> Placement Type (PLT) – Defines the memory placement guarantee of this
> FLUSH. Multiple bits may be set in this field. Values are as follows:
> • Bit 0 if set to '1' indicated that the FLUSH should guarantee Global
> Visibility.
> • Bit 1 if set to '1' indicated that the FLUSH should guarantee
> Persistence.
> • Bits 3:2 are reserved
>
> [1]: https://www.infinibandta.org/ibta-specification/ # login required
> [2]: https://www.infinibandta.org/wp-content/uploads/2021/08/IBTA-
> Overview-of-IBTA-Volume-1-Release-1.5-and-MPE-2021-08-17-Secure.pptx
>
> CC: Jason Gunthorpe <jgg@ziepe.ca>
> CC: Zhu Yanjun <zyjzyj2000@gmail.com
> CC: Leon Romanovsky <leon@kernel.org>
> CC: Bob Pearson <rpearsonhpe@gmail.com>
> CC: Weihang Li <liweihang@huawei.com>
> CC: Mark Bloch <mbloch@nvidia.com>
> CC: Wenpeng Liang <liangwenpeng@huawei.com>
> CC: Aharon Landau <aharonl@nvidia.com>
> CC: linux-rdma@vger.kernel.org
> CC: linux-kernel@vger.kernel.org
>
> Li Zhijian (10):
> RDMA: mr: Introduce is_pmem
> RDMA: Allow registering MR with flush access flags
> RDMA/rxe: Allow registering FLUSH flags for supported device only
> RDMA/rxe: Enable IB_DEVICE_RDMA_FLUSH for rxe device
> RDMA/rxe: Allow registering persistent flag for pmem MR only
> RDMA/rxe: Implement RC RDMA FLUSH service in requester side
> RDMA/rxe: Set BTH's SE to zero for FLUSH packet
> RDMA/rxe: Implement flush execution in responder side
> RDMA/rxe: Implement flush completion
> RDMA/rxe: Add RD FLUSH service support
>
> drivers/infiniband/core/uverbs_cmd.c | 16 +++
> drivers/infiniband/sw/rxe/rxe_comp.c | 4 +-
> drivers/infiniband/sw/rxe/rxe_hdr.h | 52 ++++++++++
> drivers/infiniband/sw/rxe/rxe_loc.h | 2 +
> drivers/infiniband/sw/rxe/rxe_mr.c | 63 +++++++++++-
> drivers/infiniband/sw/rxe/rxe_opcode.c | 33 ++++++
> drivers/infiniband/sw/rxe/rxe_opcode.h | 3 +
> drivers/infiniband/sw/rxe/rxe_param.h | 3 +-
> drivers/infiniband/sw/rxe/rxe_req.c | 14 ++-
> drivers/infiniband/sw/rxe/rxe_resp.c | 131 +++++++++++++++++++++++-
> include/rdma/ib_pack.h | 3 +
> include/rdma/ib_verbs.h | 22 +++-
> include/uapi/rdma/ib_user_ioctl_verbs.h | 2 +
> include/uapi/rdma/ib_user_verbs.h | 18 ++++
> include/uapi/rdma/rdma_user_rxe.h | 6 ++
> 15 files changed, 362 insertions(+), 10 deletions(-)
>
> --
> 2.31.1
>
>

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