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Message-ID: <093ee42f-4dd5-4f52-b7a5-ba5e22b18bdc@linux.dev>
Date: Sat, 10 May 2025 06:43:17 +0200
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: Daisuke Matsuda <dskmtsd@...il.com>, linux-kernel@...r.kernel.org,
linux-rdma@...r.kernel.org, leon@...nel.org, jgg@...pe.ca,
zyjzyj2000@...il.com
Subject: Re: [PATCH for-next v2 1/2] RDMA/rxe: Implement synchronous prefetch
for ODP MRs
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 <dskmtsd@...il.com>
>>> ---
>>> 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"?
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);
>>> +}
>>
>
--
Best Regards,
Yanjun.Zhu
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