[PATCH for-next v4 1/2] RDMA/rxe: Implement synchronous prefetch for ODP MRs

Daisuke Matsuda
2025-05-22T11:20:19Z

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 supported subsequently.

Signed-off-by: Daisuke Matsuda <dskmtsd@gmail.com>
Reviewed-by: Zhu Yanjun <yanjun.zhu@linux.dev>
---
drivers/infiniband/sw/rxe/rxe.c | 7 +++
drivers/infiniband/sw/rxe/rxe_loc.h | 10 ++++
drivers/infiniband/sw/rxe/rxe_odp.c | 82 +++++++++++++++++++++++++++++
3 files changed, 99 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 a1416626f61a..c723d8a6cfec 100644
--- a/drivers/infiniband/sw/rxe/rxe_odp.c
+++ b/drivers/infiniband/sw/rxe/rxe_odp.c
@@ -422,3 +422,85 @@ 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);
+ int ret = 0;
+ u32 i;
+
+ 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) {
+ 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 to be added in the next patch */
+ return -EOPNOTSUPP;
+}
+
+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);
+}
--
2.43.0