Re: [RFC PATCH rdma-next 00/10] RDMA/rxe: Add RDMA FLUSH operation
From: Tom Talpey
Date: Wed Dec 29 2021 - 09:35:12 EST
On 12/29/2021 3:49 AM, Gromadzki, Tomasz wrote:
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.
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)
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
-----Original Message-----
From: Li Zhijian <lizhijian@xxxxxxxxxxxxxx>
Sent: Tuesday, December 28, 2021 9:07 AM
To: linux-rdma@xxxxxxxxxxxxxxx; zyjzyj2000@xxxxxxxxx; jgg@xxxxxxxx;
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Cc: linux-kernel@xxxxxxxxxxxxxxx; mbloch@xxxxxxxxxx;
liweihang@xxxxxxxxxx; liangwenpeng@xxxxxxxxxx;
yangx.jy@xxxxxxxxxxxxxx; rpearsonhpe@xxxxxxxxx; y-goto@xxxxxxxxxxx; Li
Zhijian <lizhijian@xxxxxxxxxxxxxx>
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@xxxxxxxx>
CC: Zhu Yanjun <zyjzyj2000@xxxxxxxxx
CC: Leon Romanovsky <leon@xxxxxxxxxx>
CC: Bob Pearson <rpearsonhpe@xxxxxxxxx>
CC: Weihang Li <liweihang@xxxxxxxxxx>
CC: Mark Bloch <mbloch@xxxxxxxxxx>
CC: Wenpeng Liang <liangwenpeng@xxxxxxxxxx>
CC: Aharon Landau <aharonl@xxxxxxxxxx>
CC: linux-rdma@xxxxxxxxxxxxxxx
CC: linux-kernel@xxxxxxxxxxxxxxx
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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