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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

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.




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:

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
• Bit 1 if set to '1' indicated that the FLUSH should guarantee
• Bits 3:2 are reserved

[1]: # login required

CC: Jason Gunthorpe <>
CC: Zhu Yanjun <
CC: Leon Romanovsky <>
CC: Bob Pearson <>
CC: Weihang Li <>
CC: Mark Bloch <>
CC: Wenpeng Liang <>
CC: Aharon Landau <>

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(-)


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