[PATCH for-next v7 5/7] RDMA/rxe: Allow registering MRs for On-Demand Paging

Daisuke Matsuda
2023-11-09T05:47:25Z

Allow userspace to register an ODP-enabled MR, in which case the flag
IB_ACCESS_ON_DEMAND is passed to rxe_reg_user_mr(). However, there is no
RDMA operation enabled right now. They will be supported later in the
subsequent two patches.

rxe_odp_do_pagefault() is called to initialize an ODP-enabled MR. It syncs
process address space from the CPU page table to the driver page table
(dma_list/pfn_list in umem_odp) when called with RXE_PAGEFAULT_SNAPSHOT
flag. Additionally, It can be used to trigger page fault when pages being
accessed are not present or do not have proper read/write permissions, and
possibly to prefetch pages in the future.

Signed-off-by: Daisuke Matsuda <matsuda-daisuke@fujitsu.com>
---
drivers/infiniband/sw/rxe/rxe.c | 7 ++
drivers/infiniband/sw/rxe/rxe_loc.h | 14 +++
drivers/infiniband/sw/rxe/rxe_mr.c | 9 +-
drivers/infiniband/sw/rxe/rxe_odp.c | 122 ++++++++++++++++++++++++++
drivers/infiniband/sw/rxe/rxe_resp.c | 15 +++-
drivers/infiniband/sw/rxe/rxe_verbs.c | 5 +-
6 files changed, 166 insertions(+), 6 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe.c b/drivers/infiniband/sw/rxe/rxe.c
index 54c723a6edda..f2284d27229b 100644
--- a/drivers/infiniband/sw/rxe/rxe.c
+++ b/drivers/infiniband/sw/rxe/rxe.c
@@ -73,6 +73,13 @@ static void rxe_init_device_param(struct rxe_dev *rxe)
rxe->ndev->dev_addr);

rxe->max_ucontext = RXE_MAX_UCONTEXT;
+
+ if (IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING)) {
+ rxe->attr.kernel_cap_flags |= IBK_ON_DEMAND_PAGING;
+
+ /* IB_ODP_SUPPORT_IMPLICIT is not supported right now. */
+ rxe->attr.odp_caps.general_caps |= IB_ODP_SUPPORT;
+ }
}

/* initialize port attributes */
diff --git a/drivers/infiniband/sw/rxe/rxe_loc.h b/drivers/infiniband/sw/rxe/rxe_loc.h
index eb867f7d0d36..4bda154a0248 100644
--- a/drivers/infiniband/sw/rxe/rxe_loc.h
+++ b/drivers/infiniband/sw/rxe/rxe_loc.h
@@ -188,4 +188,18 @@ static inline unsigned int wr_opcode_mask(int opcode, struct rxe_qp *qp)
return rxe_wr_opcode_info[opcode].mask[qp->ibqp.qp_type];
}

+/* rxe_odp.c */
+#ifdef CONFIG_INFINIBAND_ON_DEMAND_PAGING
+int rxe_odp_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length,
+ u64 iova, int access_flags, struct rxe_mr *mr);
+#else /* CONFIG_INFINIBAND_ON_DEMAND_PAGING */
+static inline int
+rxe_odp_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length, u64 iova,
+ int access_flags, struct rxe_mr *mr)
+{
+ return -EOPNOTSUPP;
+}
+
+#endif /* CONFIG_INFINIBAND_ON_DEMAND_PAGING */
+
#endif /* RXE_LOC_H */
diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
index 86b1908d304b..384cb4ba1f2d 100644
--- a/drivers/infiniband/sw/rxe/rxe_mr.c
+++ b/drivers/infiniband/sw/rxe/rxe_mr.c
@@ -318,7 +318,10 @@ int rxe_mr_copy(struct rxe_mr *mr, u64 iova, void *addr,
return err;
}

- return rxe_mr_copy_xarray(mr, iova, addr, length, dir);
+ if (mr->umem->is_odp)
+ return -EOPNOTSUPP;
+ else
+ return rxe_mr_copy_xarray(mr, iova, addr, length, dir);
}

/* copy data in or out of a wqe, i.e. sg list
@@ -527,6 +530,10 @@ int rxe_mr_do_atomic_write(struct rxe_mr *mr, u64 iova, u64 value)
struct page *page;
u64 *va;

+ /* ODP is not supported right now. WIP. */
+ if (mr->umem->is_odp)
+ return RESPST_ERR_UNSUPPORTED_OPCODE;
+
/* See IBA oA19-28 */
if (unlikely(mr->state != RXE_MR_STATE_VALID)) {
rxe_dbg_mr(mr, "mr not in valid state");
diff --git a/drivers/infiniband/sw/rxe/rxe_odp.c b/drivers/infiniband/sw/rxe/rxe_odp.c
index ea55b79be0c6..c5e24901c141 100644
--- a/drivers/infiniband/sw/rxe/rxe_odp.c
+++ b/drivers/infiniband/sw/rxe/rxe_odp.c
@@ -9,6 +9,8 @@

#include "rxe.h"

+#define RXE_ODP_WRITABLE_BIT 1UL
+
static void rxe_mr_unset_xarray(struct rxe_mr *mr, unsigned long start,
unsigned long end)
{
@@ -25,6 +27,29 @@ static void rxe_mr_unset_xarray(struct rxe_mr *mr, unsigned long start,
xas_unlock(&xas);
}

+static void rxe_mr_set_xarray(struct rxe_mr *mr, unsigned long start,
+ unsigned long end, unsigned long *pfn_list)
+{
+ unsigned long upper = rxe_mr_iova_to_index(mr, end - 1);
+ unsigned long lower = rxe_mr_iova_to_index(mr, start);
+ void *page, *entry;
+
+ XA_STATE(xas, &mr->page_list, lower);
+
+ xas_lock(&xas);
+ while (xas.xa_index <= upper) {
+ if (pfn_list[xas.xa_index] & HMM_PFN_WRITE) {
+ page = xa_tag_pointer(hmm_pfn_to_page(pfn_list[xas.xa_index]),
+ RXE_ODP_WRITABLE_BIT);
+ } else
+ page = hmm_pfn_to_page(pfn_list[xas.xa_index]);
+
+ xas_store(&xas, page);
+ entry = xas_next(&xas);
+ }
+ xas_unlock(&xas);
+}
+
static bool rxe_ib_invalidate_range(struct mmu_interval_notifier *mni,
const struct mmu_notifier_range *range,
unsigned long cur_seq)
@@ -55,3 +80,100 @@ static bool rxe_ib_invalidate_range(struct mmu_interval_notifier *mni,
const struct mmu_interval_notifier_ops rxe_mn_ops = {
.invalidate = rxe_ib_invalidate_range,
};
+
+#define RXE_PAGEFAULT_RDONLY BIT(1)
+#define RXE_PAGEFAULT_SNAPSHOT BIT(2)
+static int rxe_odp_do_pagefault_and_lock(struct rxe_mr *mr, u64 user_va, int bcnt, u32 flags)
+{
+ struct ib_umem_odp *umem_odp = to_ib_umem_odp(mr->umem);
+ bool fault = !(flags & RXE_PAGEFAULT_SNAPSHOT);
+ u64 access_mask;
+ int np;
+
+ access_mask = ODP_READ_ALLOWED_BIT;
+ if (umem_odp->umem.writable && !(flags & RXE_PAGEFAULT_RDONLY))
+ access_mask |= ODP_WRITE_ALLOWED_BIT;
+
+ /*
+ * ib_umem_odp_map_dma_and_lock() locks umem_mutex on success.
+ * Callers must release the lock later to let invalidation handler
+ * do its work again.
+ */
+ np = ib_umem_odp_map_dma_and_lock(umem_odp, user_va, bcnt,
+ access_mask, fault);
+ if (np < 0)
+ return np;
+
+ /*
+ * umem_mutex is still locked here, so we can use hmm_pfn_to_page()
+ * safely to fetch pages in the range.
+ */
+ rxe_mr_set_xarray(mr, user_va, user_va + bcnt, umem_odp->pfn_list);
+
+ return np;
+}
+
+static int rxe_odp_init_pages(struct rxe_mr *mr)
+{
+ struct ib_umem_odp *umem_odp = to_ib_umem_odp(mr->umem);
+ int ret;
+
+ ret = rxe_odp_do_pagefault_and_lock(mr, mr->umem->address,
+ mr->umem->length,
+ RXE_PAGEFAULT_SNAPSHOT);
+
+ if (ret >= 0)
+ mutex_unlock(&umem_odp->umem_mutex);
+
+ return ret >= 0 ? 0 : ret;
+}
+
+int rxe_odp_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length,
+ u64 iova, int access_flags, struct rxe_mr *mr)
+{
+ struct ib_umem_odp *umem_odp;
+ int err;
+
+ if (!IS_ENABLED(CONFIG_INFINIBAND_ON_DEMAND_PAGING))
+ return -EOPNOTSUPP;
+
+ rxe_mr_init(access_flags, mr);
+
+ xa_init(&mr->page_list);
+
+ if (!start && length == U64_MAX) {
+ if (iova != 0)
+ return -EINVAL;
+ if (!(rxe->attr.odp_caps.general_caps & IB_ODP_SUPPORT_IMPLICIT))
+ return -EINVAL;
+
+ /* Never reach here, for implicit ODP is not implemented. */
+ }
+
+ umem_odp = ib_umem_odp_get(&rxe->ib_dev, start, length, access_flags,
+ &rxe_mn_ops);
+ if (IS_ERR(umem_odp)) {
+ rxe_dbg_mr(mr, "Unable to create umem_odp err = %d\n",
+ (int)PTR_ERR(umem_odp));
+ return PTR_ERR(umem_odp);
+ }
+
+ umem_odp->private = mr;
+
+ mr->umem = &umem_odp->umem;
+ mr->access = access_flags;
+ mr->ibmr.length = length;
+ mr->ibmr.iova = iova;
+ mr->page_offset = ib_umem_offset(&umem_odp->umem);
+
+ err = rxe_odp_init_pages(mr);
+ if (err) {
+ ib_umem_odp_release(umem_odp);
+ return err;
+ }
+
+ mr->state = RXE_MR_STATE_VALID;
+ mr->ibmr.type = IB_MR_TYPE_USER;
+
+ return err;
+}
diff --git a/drivers/infiniband/sw/rxe/rxe_resp.c b/drivers/infiniband/sw/rxe/rxe_resp.c
index 969e057bbfd1..9159f1bdfc6f 100644
--- a/drivers/infiniband/sw/rxe/rxe_resp.c
+++ b/drivers/infiniband/sw/rxe/rxe_resp.c
@@ -635,6 +635,10 @@ static enum resp_states process_flush(struct rxe_qp *qp,
struct rxe_mr *mr = qp->resp.mr;
struct resp_res *res = qp->resp.res;

+ /* ODP is not supported right now. WIP. */
+ if (mr->umem->is_odp)
+ return RESPST_ERR_UNSUPPORTED_OPCODE;
+
/* oA19-14, oA19-15 */
if (res && res->replay)
return RESPST_ACKNOWLEDGE;
@@ -688,10 +692,13 @@ static enum resp_states atomic_reply(struct rxe_qp *qp,
if (!res->replay) {
u64 iova = qp->resp.va + qp->resp.offset;

- err = rxe_mr_do_atomic_op(mr, iova, pkt->opcode,
- atmeth_comp(pkt),
- atmeth_swap_add(pkt),
- &res->atomic.orig_val);
+ if (mr->umem->is_odp)
+ err = RESPST_ERR_UNSUPPORTED_OPCODE;
+ else
+ err = rxe_mr_do_atomic_op(mr, iova, pkt->opcode,
+ atmeth_comp(pkt),
+ atmeth_swap_add(pkt),
+ &res->atomic.orig_val);
if (err)
return err;

diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
index 48f86839d36a..192ad835c712 100644
--- a/drivers/infiniband/sw/rxe/rxe_verbs.c
+++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
@@ -1278,7 +1278,10 @@ static struct ib_mr *rxe_reg_user_mr(struct ib_pd *ibpd, u64 start,
mr->ibmr.pd = ibpd;
mr->ibmr.device = ibpd->device;

- err = rxe_mr_init_user(rxe, start, length, iova, access, mr);
+ if (access & IB_ACCESS_ON_DEMAND)
+ err = rxe_odp_mr_init_user(rxe, start, length, iova, access, mr);
+ else
+ err = rxe_mr_init_user(rxe, start, length, iova, access, mr);
if (err) {
rxe_dbg_mr(mr, "reg_user_mr failed, err = %d", err);
goto err_cleanup;
--
2.39.1