On 12/29/2021 3:49 AM, Gromadzki, Tomasz wrote:

1)

quoted

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.

I agree. The Flush operation does not access any local memory and
therefore an SGE is inappropriate. Better to pass the actual
Flush parameters, i.e. add the length. See next comment.

2)

quoted

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

Also agree. The remote length of the subregion to be flushed is
a required parameter and should be passed here.

Is it really necessary to promote the type and level to full 32-bit
fields in the API? In the protocol, these are just 4 bits and 2 bits,
respectively, and are packed together into a singe 32-bit FETH field.

Tom.

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

quoted

-----Original Message-----
From: Li Zhijian <redacted>
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 [off-list ref]
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 <redacted>
CC: Weihang Li <redacted>
CC: Mark Bloch <mbloch@nvidia.com>
CC: Wenpeng Liang <redacted>
CC: Aharon Landau <redacted>
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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