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[119.244.79.106]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-74237704ff3sm3795155b3a.1.2025.05.10.19.06.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 10 May 2025 19:06:13 -0700 (PDT) Message-ID: Date: Sun, 11 May 2025 11:06:10 +0900 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH for-next v2 1/2] RDMA/rxe: Implement synchronous prefetch for ODP MRs To: Zhu Yanjun Cc: linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, leon@kernel.org, jgg@ziepe.ca, zyjzyj2000@gmail.com References: <20250503134224.4867-1-dskmtsd@gmail.com> <20250503134224.4867-2-dskmtsd@gmail.com> <093ee42f-4dd5-4f52-b7a5-ba5e22b18bdc@linux.dev> Content-Language: en-US From: Daisuke Matsuda In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2025/05/10 17:04, Greg Sword wrote: > On Sat, May 10, 2025 at 3:19 PM Daisuke Matsuda wrote: >> >> On 2025/05/10 13:43, Zhu Yanjun wrote: >>> >>> 在 2025/5/10 4:46, Daisuke Matsuda 写道: >>>> On 2025/05/10 0:19, Zhu Yanjun wrote: >>>>> On 03.05.25 15:42, Daisuke Matsuda wrote: >>>>>> Minimal implementation of ibv_advise_mr(3) requires synchronous calls being >>>>>> successful with the IBV_ADVISE_MR_FLAG_FLUSH flag. Asynchronous requests, >>>>>> which are best-effort, will be added subsequently. >>>>>> >>>>>> Signed-off-by: Daisuke Matsuda >>>>>> --- >>>>>> drivers/infiniband/sw/rxe/rxe.c | 7 +++ >>>>>> drivers/infiniband/sw/rxe/rxe_loc.h | 10 ++++ >>>>>> drivers/infiniband/sw/rxe/rxe_odp.c | 86 +++++++++++++++++++++++++++++ >>>>>> 3 files changed, 103 insertions(+) >>>>>> >>>>>> diff --git a/drivers/infiniband/sw/rxe/rxe.c b/drivers/infiniband/sw/rxe/rxe.c >>>>>> index 3a77d6db1720..e891199cbdef 100644 >>>>>> --- a/drivers/infiniband/sw/rxe/rxe.c >>>>>> +++ b/drivers/infiniband/sw/rxe/rxe.c >>>>>> @@ -34,6 +34,10 @@ void rxe_dealloc(struct ib_device *ib_dev) >>>>>> mutex_destroy(&rxe->usdev_lock); >>>>>> } >>>>>> +static const struct ib_device_ops rxe_ib_dev_odp_ops = { >>>>>> + .advise_mr = rxe_ib_advise_mr, >>>>>> +}; >>>>>> + >>>>>> /* initialize rxe device parameters */ >>>>>> static void rxe_init_device_param(struct rxe_dev *rxe, struct net_device *ndev) >>>>>> { >>>>>> @@ -103,6 +107,9 @@ static void rxe_init_device_param(struct rxe_dev *rxe, struct net_device *ndev) >>>>>> rxe->attr.odp_caps.per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_SRQ_RECV; >>>>>> rxe->attr.odp_caps.per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_FLUSH; >>>>>> rxe->attr.odp_caps.per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_ATOMIC_WRITE; >>>>>> + >>>>>> + /* set handler for ODP prefetching API - ibv_advise_mr(3) */ >>>>>> + ib_set_device_ops(&rxe->ib_dev, &rxe_ib_dev_odp_ops); >>>>>> } >>>>>> } >>>>>> diff --git a/drivers/infiniband/sw/rxe/rxe_loc.h b/drivers/infiniband/sw/rxe/rxe_loc.h >>>>>> index f7dbb9cddd12..21b070f3dbb8 100644 >>>>>> --- a/drivers/infiniband/sw/rxe/rxe_loc.h >>>>>> +++ b/drivers/infiniband/sw/rxe/rxe_loc.h >>>>>> @@ -197,6 +197,9 @@ enum resp_states rxe_odp_atomic_op(struct rxe_mr *mr, u64 iova, int opcode, >>>>>> int rxe_odp_flush_pmem_iova(struct rxe_mr *mr, u64 iova, >>>>>> unsigned int length); >>>>>> enum resp_states rxe_odp_do_atomic_write(struct rxe_mr *mr, u64 iova, u64 value); >>>>>> +int rxe_ib_advise_mr(struct ib_pd *pd, enum ib_uverbs_advise_mr_advice advice, >>>>>> + u32 flags, struct ib_sge *sg_list, u32 num_sge, >>>>>> + struct uverbs_attr_bundle *attrs); >>>>>> #else /* CONFIG_INFINIBAND_ON_DEMAND_PAGING */ >>>>>> static inline int >>>>>> rxe_odp_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length, u64 iova, >>>>>> @@ -225,6 +228,13 @@ static inline enum resp_states rxe_odp_do_atomic_write(struct rxe_mr *mr, >>>>>> { >>>>>> return RESPST_ERR_UNSUPPORTED_OPCODE; >>>>>> } >>>>>> +static inline int rxe_ib_advise_mr(struct ib_pd *pd, enum ib_uverbs_advise_mr_advice advice, >>>>>> + u32 flags, struct ib_sge *sg_list, u32 num_sge, >>>>>> + struct uverbs_attr_bundle *attrs) >>>>>> +{ >>>>>> + return -EOPNOTSUPP; >>>>>> +} >>>>>> + >>>>>> #endif /* CONFIG_INFINIBAND_ON_DEMAND_PAGING */ >>>>>> #endif /* RXE_LOC_H */ >>>>>> diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c >>>>>> index 6149d9ffe7f7..e5c60b061d7e 100644 >>>>>> --- a/drivers/infiniband/sw/rxe/rxe_odp.c >>>>>> +++ b/drivers/infiniband/sw/rxe/rxe_odp.c >>>>>> @@ -424,3 +424,89 @@ enum resp_states rxe_odp_do_atomic_write(struct rxe_mr *mr, u64 iova, u64 value) >>>>>> return RESPST_NONE; >>>>>> } >>>>>> + >>>>>> +static int rxe_ib_prefetch_sg_list(struct ib_pd *ibpd, >>>>>> + enum ib_uverbs_advise_mr_advice advice, >>>>>> + u32 pf_flags, struct ib_sge *sg_list, >>>>>> + u32 num_sge) >>>>>> +{ >>>>>> + struct rxe_pd *pd = container_of(ibpd, struct rxe_pd, ibpd); >>>>>> + unsigned int i; >>>>>> + int ret = 0; >>>>>> + >>>>>> + for (i = 0; i < num_sge; ++i) { >>>>>> + struct rxe_mr *mr; >>>>>> + struct ib_umem_odp *umem_odp; >>>>>> + >>>>>> + mr = lookup_mr(pd, IB_ACCESS_LOCAL_WRITE, >>>>>> + sg_list[i].lkey, RXE_LOOKUP_LOCAL); >>>>>> + >>>>>> + if (IS_ERR(mr)) { >>>>>> + rxe_dbg_pd(pd, "mr with lkey %x not found\n", sg_list[i].lkey); >>>>>> + return PTR_ERR(mr); >>>>>> + } >>>>>> + >>>>>> + if (advice == IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_WRITE && >>>>>> + !mr->umem->writable) { >>>>>> + rxe_dbg_mr(mr, "missing write permission\n"); >>>>>> + rxe_put(mr); >>>>>> + return -EPERM; >>>>>> + } >>>>>> + >>>>>> + ret = rxe_odp_do_pagefault_and_lock(mr, sg_list[i].addr, >>>>>> + sg_list[i].length, pf_flags); >>>>>> + if (ret < 0) { >>>>>> + if (sg_list[i].length == 0) >>>>>> + continue; >>>>>> + >>>>>> + rxe_dbg_mr(mr, "failed to prefetch the mr\n"); >>>>>> + rxe_put(mr); >>>>>> + return ret; >>>>>> + } >>>>>> + >>>>>> + umem_odp = to_ib_umem_odp(mr->umem); >>>>>> + mutex_unlock(&umem_odp->umem_mutex); >>>>>> + >>>>>> + rxe_put(mr); >>>>>> + } >>>>>> + >>>>>> + return 0; >>>>>> +} >>>>>> + >>>>>> +static int rxe_ib_advise_mr_prefetch(struct ib_pd *ibpd, >>>>>> + enum ib_uverbs_advise_mr_advice advice, >>>>>> + u32 flags, struct ib_sge *sg_list, u32 num_sge) >>>>>> +{ >>>>>> + u32 pf_flags = RXE_PAGEFAULT_DEFAULT; >>>>>> + >>>>>> + if (advice == IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH) >>>>>> + pf_flags |= RXE_PAGEFAULT_RDONLY; >>>>>> + >>>>>> + if (advice == IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_NO_FAULT) >>>>>> + pf_flags |= RXE_PAGEFAULT_SNAPSHOT; >>>>>> + >>>>>> + /* Synchronous call */ >>>>>> + if (flags & IB_UVERBS_ADVISE_MR_FLAG_FLUSH) >>>>>> + return rxe_ib_prefetch_sg_list(ibpd, advice, pf_flags, sg_list, >>>>>> + num_sge); >>>>>> + >>>>>> + /* Asynchronous call is "best-effort" */ >>>>> >>>>> Asynchronous call is not implemented now, why does this comment appear? >>>> >>>> Even without the 2nd patch, async calls are reported as successful. >>> >>> >>> Async call is not implemented. How to call "async calls are reported as successful"? >> >> Please see the manual. >> cf. https://manpages.debian.org/testing/libibverbs-dev/ibv_advise_mr.3.en.html >> >> If IBV_ADVISE_MR_FLAG_FLUSH is not given to 'flags' parameter, >> then this function 'rxe_ib_advise_mr_prefetch()' simply returns 0. >> Consequently, ibv_advise_mr(3) and underlying ioctl(2) get no error. >> This behaviour is allowd in the spec as I quoted in the last reply. > > The functionality wasn't implemented, you added the comments first. > You're still weaseling when people point this out. > >> >> It might be nice to return -EOPNOTSUPP just below the comment instead, >> but not doing so is acceptable according to the spec. Additionally, >> such change will be overwritten in the next patch after all. > > Move comments to the next patch. In this patch, return -EOPNOTSUPP. Any opinion from Zhu? I may post a new revision to change the intermediate code, but the final result after applying the patchset will be the same. You are the maintainer of rxe, so I will follow that. Thanks, Daisuke > > --G-- > >> >> Thanks, >> Daisuke >> >>> >>> >>> Zhu Yanjun >>> >>>> The comment is inserted to show the reason, which is based on the >>>> description from 'man 3 ibv_advise_mr' as follows: >>>> === >>>> An application may pre-fetch any address range within an ODP MR when using the IBV_ADVISE_MR_ADVICE_PREFETCH or IBV_ADVISE_MR_ADVICE_PREFETCH_WRITE advice. Semantically, this operation is best-effort. That means the kernel does not guarantee that underlying pages are updated in the HCA or the pre-fetched pages would remain resident. >>>> === >>>> >>>> Thanks, >>>> Daisuke >>>> >>>>> >>>>> Zhu Yanjun >>>>> >>>>>> + >>>>>> + return 0; >>>>>> +} >>>>>> + >>>>>> +int rxe_ib_advise_mr(struct ib_pd *ibpd, >>>>>> + enum ib_uverbs_advise_mr_advice advice, >>>>>> + u32 flags, >>>>>> + struct ib_sge *sg_list, >>>>>> + u32 num_sge, >>>>>> + struct uverbs_attr_bundle *attrs) >>>>>> +{ >>>>>> + if (advice != IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH && >>>>>> + advice != IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_WRITE && >>>>>> + advice != IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_NO_FAULT) >>>>>> + return -EOPNOTSUPP; >>>>>> + >>>>>> + return rxe_ib_advise_mr_prefetch(ibpd, advice, flags, >>>>>> + sg_list, num_sge); >>>>>> +} >>>>> >>>> >> >>