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SubjectRe: [RFC PATCH rdma-next 00/10] RDMA/rxe: Add RDMA FLUSH operation
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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@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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