IB/mlx5: Handle page faults

This patch implement a page fault handler (leaving the pages pinned as
of time being).  The page fault handler handles initiator and responder
page faults for UD/RC transports, for send/receive operations, as well
as RDMA read/write initiator support.

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Shachar Raindel <raindel@mellanox.com>
Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

2 files changed, 415 insertions, 0 deletions

diff --git a/drivers/infiniband/hw/mlx5/odp.c b/drivers/infiniband/hw/mlx5/odp.c
index 63bbdba396f1..bd1dbe5ebc15 100644
--- a/drivers/infiniband/hw/mlx5/odp.c
+++ b/drivers/infiniband/hw/mlx5/odp.c
@@ -30,6 +30,9 @@
  * SOFTWARE.
  */
 
+#include <rdma/ib_umem.h>
+#include <rdma/ib_umem_odp.h>
+
 #include "mlx5_ib.h"
 
 struct workqueue_struct *mlx5_ib_page_fault_wq;
@@ -85,12 +88,417 @@ static void mlx5_ib_page_fault_resume(struct mlx5_ib_qp *qp,
                        qp->mqp.qpn);
 }
 
+/*
+ * Handle a single data segment in a page-fault WQE.
+ *
+ * Returns number of pages retrieved on success. The caller will continue to
+ * the next data segment.
+ * Can return the following error codes:
+ * -EAGAIN to designate a temporary error. The caller will abort handling the
+ *  page fault and resolve it.
+ * -EFAULT when there's an error mapping the requested pages. The caller will
+ *  abort the page fault handling and possibly move the QP to an error state.
+ * On other errors the QP should also be closed with an error.
+ */
+static int pagefault_single_data_segment(struct mlx5_ib_qp *qp,
+                                         struct mlx5_ib_pfault *pfault,
+                                         u32 key, u64 io_virt, size_t bcnt,
+                                         u32 *bytes_mapped)
+{
+        struct mlx5_ib_dev *mib_dev = to_mdev(qp->ibqp.pd->device);
+        int srcu_key;
+        unsigned int current_seq;
+        u64 start_idx;
+        int npages = 0, ret = 0;
+        struct mlx5_ib_mr *mr;
+        u64 access_mask = ODP_READ_ALLOWED_BIT;
+
+        srcu_key = srcu_read_lock(&mib_dev->mr_srcu);
+        mr = mlx5_ib_odp_find_mr_lkey(mib_dev, key);
+        /*
+         * If we didn't find the MR, it means the MR was closed while we were
+         * handling the ODP event. In this case we return -EFAULT so that the
+         * QP will be closed.
+         */
+        if (!mr || !mr->ibmr.pd) {
+                pr_err("Failed to find relevant mr for lkey=0x%06x, probably the MR was destroyed\n",
+                       key);
+                ret = -EFAULT;
+                goto srcu_unlock;
+        }
+        if (!mr->umem->odp_data) {
+                pr_debug("skipping non ODP MR (lkey=0x%06x) in page fault handler.\n",
+                         key);
+                if (bytes_mapped)
+                        *bytes_mapped +=
+                                (bcnt - pfault->mpfault.bytes_committed);
+                goto srcu_unlock;
+        }
+        if (mr->ibmr.pd != qp->ibqp.pd) {
+                pr_err("Page-fault with different PDs for QP and MR.\n");
+                ret = -EFAULT;
+                goto srcu_unlock;
+        }
+
+        current_seq = ACCESS_ONCE(mr->umem->odp_data->notifiers_seq);
+
+        /*
+         * Avoid branches - this code will perform correctly
+         * in all iterations (in iteration 2 and above,
+         * bytes_committed == 0).
+         */
+        io_virt += pfault->mpfault.bytes_committed;
+        bcnt -= pfault->mpfault.bytes_committed;
+
+        start_idx = (io_virt - (mr->mmr.iova & PAGE_MASK)) >> PAGE_SHIFT;
+
+        if (mr->umem->writable)
+                access_mask |= ODP_WRITE_ALLOWED_BIT;
+        npages = ib_umem_odp_map_dma_pages(mr->umem, io_virt, bcnt,
+                                           access_mask, current_seq);
+        if (npages < 0) {
+                ret = npages;
+                goto srcu_unlock;
+        }
+
+        if (npages > 0) {
+                mutex_lock(&mr->umem->odp_data->umem_mutex);
+                /*
+                 * No need to check whether the MTTs really belong to
+                 * this MR, since ib_umem_odp_map_dma_pages already
+                 * checks this.
+                 */
+                ret = mlx5_ib_update_mtt(mr, start_idx, npages, 0);
+                mutex_unlock(&mr->umem->odp_data->umem_mutex);
+                if (ret < 0) {
+                        pr_err("Failed to update mkey page tables\n");
+                        goto srcu_unlock;
+                }
+
+                if (bytes_mapped) {
+                        u32 new_mappings = npages * PAGE_SIZE -
+                                (io_virt - round_down(io_virt, PAGE_SIZE));
+                        *bytes_mapped += min_t(u32, new_mappings, bcnt);
+                }
+        }
+
+srcu_unlock:
+        srcu_read_unlock(&mib_dev->mr_srcu, srcu_key);
+        pfault->mpfault.bytes_committed = 0;
+        return ret ? ret : npages;
+}
+
+/**
+ * Parse a series of data segments for page fault handling.
+ *
+ * @qp the QP on which the fault occurred.
+ * @pfault contains page fault information.
+ * @wqe points at the first data segment in the WQE.
+ * @wqe_end points after the end of the WQE.
+ * @bytes_mapped receives the number of bytes that the function was able to
+ *               map. This allows the caller to decide intelligently whether
+ *               enough memory was mapped to resolve the page fault
+ *               successfully (e.g. enough for the next MTU, or the entire
+ *               WQE).
+ * @total_wqe_bytes receives the total data size of this WQE in bytes (minus
+ *                  the committed bytes).
+ *
+ * Returns the number of pages loaded if positive, zero for an empty WQE, or a
+ * negative error code.
+ */
+static int pagefault_data_segments(struct mlx5_ib_qp *qp,
+                                   struct mlx5_ib_pfault *pfault, void *wqe,
+                                   void *wqe_end, u32 *bytes_mapped,
+                                   u32 *total_wqe_bytes, int receive_queue)
+{
+        int ret = 0, npages = 0;
+        u64 io_virt;
+        u32 key;
+        u32 byte_count;
+        size_t bcnt;
+        int inline_segment;
+
+        /* Skip SRQ next-WQE segment. */
+        if (receive_queue && qp->ibqp.srq)
+                wqe += sizeof(struct mlx5_wqe_srq_next_seg);
+
+        if (bytes_mapped)
+                *bytes_mapped = 0;
+        if (total_wqe_bytes)
+                *total_wqe_bytes = 0;
+
+        while (wqe < wqe_end) {
+                struct mlx5_wqe_data_seg *dseg = wqe;
+
+                io_virt = be64_to_cpu(dseg->addr);
+                key = be32_to_cpu(dseg->lkey);
+                byte_count = be32_to_cpu(dseg->byte_count);
+                inline_segment = !!(byte_count &  MLX5_INLINE_SEG);
+                bcnt           = byte_count & ~MLX5_INLINE_SEG;
+
+                if (inline_segment) {
+                        bcnt = bcnt & MLX5_WQE_INLINE_SEG_BYTE_COUNT_MASK;
+                        wqe += ALIGN(sizeof(struct mlx5_wqe_inline_seg) + bcnt,
+                                     16);
+                } else {
+                        wqe += sizeof(*dseg);
+                }
+
+                /* receive WQE end of sg list. */
+                if (receive_queue && bcnt == 0 && key == MLX5_INVALID_LKEY &&
+                    io_virt == 0)
+                        break;
+
+                if (!inline_segment && total_wqe_bytes) {
+                        *total_wqe_bytes += bcnt - min_t(size_t, bcnt,
+                                        pfault->mpfault.bytes_committed);
+                }
+
+                /* A zero length data segment designates a length of 2GB. */
+                if (bcnt == 0)
+                        bcnt = 1U << 31;
+
+                if (inline_segment || bcnt <= pfault->mpfault.bytes_committed) {
+                        pfault->mpfault.bytes_committed -=
+                                min_t(size_t, bcnt,
+                                      pfault->mpfault.bytes_committed);
+                        continue;
+                }
+
+                ret = pagefault_single_data_segment(qp, pfault, key, io_virt,
+                                                    bcnt, bytes_mapped);
+                if (ret < 0)
+                        break;
+                npages += ret;
+        }
+
+        return ret < 0 ? ret : npages;
+}
+
+/*
+ * Parse initiator WQE. Advances the wqe pointer to point at the
+ * scatter-gather list, and set wqe_end to the end of the WQE.
+ */
+static int mlx5_ib_mr_initiator_pfault_handler(
+        struct mlx5_ib_qp *qp, struct mlx5_ib_pfault *pfault,
+        void **wqe, void **wqe_end, int wqe_length)
+{
+        struct mlx5_ib_dev *dev = to_mdev(qp->ibqp.pd->device);
+        struct mlx5_wqe_ctrl_seg *ctrl = *wqe;
+        u16 wqe_index = pfault->mpfault.wqe.wqe_index;
+        unsigned ds, opcode;
+#if defined(DEBUG)
+        u32 ctrl_wqe_index, ctrl_qpn;
+#endif
+
+        ds = be32_to_cpu(ctrl->qpn_ds) & MLX5_WQE_CTRL_DS_MASK;
+        if (ds * MLX5_WQE_DS_UNITS > wqe_length) {
+                mlx5_ib_err(dev, "Unable to read the complete WQE. ds = 0x%x, ret = 0x%x\n",
+                            ds, wqe_length);
+                return -EFAULT;
+        }
+
+        if (ds == 0) {
+                mlx5_ib_err(dev, "Got WQE with zero DS. wqe_index=%x, qpn=%x\n",
+                            wqe_index, qp->mqp.qpn);
+                return -EFAULT;
+        }
+
+#if defined(DEBUG)
+        ctrl_wqe_index = (be32_to_cpu(ctrl->opmod_idx_opcode) &
+                        MLX5_WQE_CTRL_WQE_INDEX_MASK) >>
+                        MLX5_WQE_CTRL_WQE_INDEX_SHIFT;
+        if (wqe_index != ctrl_wqe_index) {
+                mlx5_ib_err(dev, "Got WQE with invalid wqe_index. wqe_index=0x%x, qpn=0x%x ctrl->wqe_index=0x%x\n",
+                            wqe_index, qp->mqp.qpn,
+                            ctrl_wqe_index);
+                return -EFAULT;
+        }
+
+        ctrl_qpn = (be32_to_cpu(ctrl->qpn_ds) & MLX5_WQE_CTRL_QPN_MASK) >>
+                MLX5_WQE_CTRL_QPN_SHIFT;
+        if (qp->mqp.qpn != ctrl_qpn) {
+                mlx5_ib_err(dev, "Got WQE with incorrect QP number. wqe_index=0x%x, qpn=0x%x ctrl->qpn=0x%x\n",
+                            wqe_index, qp->mqp.qpn,
+                            ctrl_qpn);
+                return -EFAULT;
+        }
+#endif /* DEBUG */
+
+        *wqe_end = *wqe + ds * MLX5_WQE_DS_UNITS;
+        *wqe += sizeof(*ctrl);
+
+        opcode = be32_to_cpu(ctrl->opmod_idx_opcode) &
+                 MLX5_WQE_CTRL_OPCODE_MASK;
+        switch (qp->ibqp.qp_type) {
+        case IB_QPT_RC:
+                switch (opcode) {
+                case MLX5_OPCODE_SEND:
+                case MLX5_OPCODE_SEND_IMM:
+                case MLX5_OPCODE_SEND_INVAL:
+                        if (!(dev->odp_caps.per_transport_caps.rc_odp_caps &
+                              IB_ODP_SUPPORT_SEND))
+                                goto invalid_transport_or_opcode;
+                        break;
+                case MLX5_OPCODE_RDMA_WRITE:
+                case MLX5_OPCODE_RDMA_WRITE_IMM:
+                        if (!(dev->odp_caps.per_transport_caps.rc_odp_caps &
+                              IB_ODP_SUPPORT_WRITE))
+                                goto invalid_transport_or_opcode;
+                        *wqe += sizeof(struct mlx5_wqe_raddr_seg);
+                        break;
+                case MLX5_OPCODE_RDMA_READ:
+                        if (!(dev->odp_caps.per_transport_caps.rc_odp_caps &
+                              IB_ODP_SUPPORT_READ))
+                                goto invalid_transport_or_opcode;
+                        *wqe += sizeof(struct mlx5_wqe_raddr_seg);
+                        break;
+                default:
+                        goto invalid_transport_or_opcode;
+                }
+                break;
+        case IB_QPT_UD:
+                switch (opcode) {
+                case MLX5_OPCODE_SEND:
+                case MLX5_OPCODE_SEND_IMM:
+                        if (!(dev->odp_caps.per_transport_caps.ud_odp_caps &
+                              IB_ODP_SUPPORT_SEND))
+                                goto invalid_transport_or_opcode;
+                        *wqe += sizeof(struct mlx5_wqe_datagram_seg);
+                        break;
+                default:
+                        goto invalid_transport_or_opcode;
+                }
+                break;
+        default:
+invalid_transport_or_opcode:
+                mlx5_ib_err(dev, "ODP fault on QP of an unsupported opcode or transport. transport: 0x%x opcode: 0x%x.\n",
+                            qp->ibqp.qp_type, opcode);
+                return -EFAULT;
+        }
+
+        return 0;
+}
+
+/*
+ * Parse responder WQE. Advances the wqe pointer to point at the
+ * scatter-gather list, and set wqe_end to the end of the WQE.
+ */
+static int mlx5_ib_mr_responder_pfault_handler(
+        struct mlx5_ib_qp *qp, struct mlx5_ib_pfault *pfault,
+        void **wqe, void **wqe_end, int wqe_length)
+{
+        struct mlx5_ib_dev *dev = to_mdev(qp->ibqp.pd->device);
+        struct mlx5_ib_wq *wq = &qp->rq;
+        int wqe_size = 1 << wq->wqe_shift;
+
+        if (qp->ibqp.srq) {
+                mlx5_ib_err(dev, "ODP fault on SRQ is not supported\n");
+                return -EFAULT;
+        }
+
+        if (qp->wq_sig) {
+                mlx5_ib_err(dev, "ODP fault with WQE signatures is not supported\n");
+                return -EFAULT;
+        }
+
+        if (wqe_size > wqe_length) {
+                mlx5_ib_err(dev, "Couldn't read all of the receive WQE's content\n");
+                return -EFAULT;
+        }
+
+        switch (qp->ibqp.qp_type) {
+        case IB_QPT_RC:
+                if (!(dev->odp_caps.per_transport_caps.rc_odp_caps &
+                      IB_ODP_SUPPORT_RECV))
+                        goto invalid_transport_or_opcode;
+                break;
+        default:
+invalid_transport_or_opcode:
+                mlx5_ib_err(dev, "ODP fault on QP of an unsupported transport. transport: 0x%x\n",
+                            qp->ibqp.qp_type);
+                return -EFAULT;
+        }
+
+        *wqe_end = *wqe + wqe_size;
+
+        return 0;
+}
+
+static void mlx5_ib_mr_wqe_pfault_handler(struct mlx5_ib_qp *qp,
+                                          struct mlx5_ib_pfault *pfault)
+{
+        struct mlx5_ib_dev *dev = to_mdev(qp->ibqp.pd->device);
+        int ret;
+        void *wqe, *wqe_end;
+        u32 bytes_mapped, total_wqe_bytes;
+        char *buffer = NULL;
+        int resume_with_error = 0;
+        u16 wqe_index = pfault->mpfault.wqe.wqe_index;
+        int requestor = pfault->mpfault.flags & MLX5_PFAULT_REQUESTOR;
+
+        buffer = (char *)__get_free_page(GFP_KERNEL);
+        if (!buffer) {
+                mlx5_ib_err(dev, "Error allocating memory for IO page fault handling.\n");
+                resume_with_error = 1;
+                goto resolve_page_fault;
+        }
+
+        ret = mlx5_ib_read_user_wqe(qp, requestor, wqe_index, buffer,
+                                    PAGE_SIZE);
+        if (ret < 0) {
+                mlx5_ib_err(dev, "Failed reading a WQE following page fault, error=%x, wqe_index=%x, qpn=%x\n",
+                            -ret, wqe_index, qp->mqp.qpn);
+                resume_with_error = 1;
+                goto resolve_page_fault;
+        }
+
+        wqe = buffer;
+        if (requestor)
+                ret = mlx5_ib_mr_initiator_pfault_handler(qp, pfault, &wqe,
+                                                          &wqe_end, ret);
+        else
+                ret = mlx5_ib_mr_responder_pfault_handler(qp, pfault, &wqe,
+                                                          &wqe_end, ret);
+        if (ret < 0) {
+                resume_with_error = 1;
+                goto resolve_page_fault;
+        }
+
+        if (wqe >= wqe_end) {
+                mlx5_ib_err(dev, "ODP fault on invalid WQE.\n");
+                resume_with_error = 1;
+                goto resolve_page_fault;
+        }
+
+        ret = pagefault_data_segments(qp, pfault, wqe, wqe_end, &bytes_mapped,
+                                      &total_wqe_bytes, !requestor);
+        if (ret == -EAGAIN) {
+                goto resolve_page_fault;
+        } else if (ret < 0 || total_wqe_bytes > bytes_mapped) {
+                mlx5_ib_err(dev, "Error getting user pages for page fault. Error: 0x%x\n",
+                            -ret);
+                resume_with_error = 1;
+                goto resolve_page_fault;
+        }
+
+resolve_page_fault:
+        mlx5_ib_page_fault_resume(qp, pfault, resume_with_error);
+        mlx5_ib_dbg(dev, "PAGE FAULT completed. QP 0x%x resume_with_error=%d, flags: 0x%x\n",
+                    qp->mqp.qpn, resume_with_error, pfault->mpfault.flags);
+
+        free_page((unsigned long)buffer);
+}
+
 void mlx5_ib_mr_pfault_handler(struct mlx5_ib_qp *qp,
                                struct mlx5_ib_pfault *pfault)
 {
         u8 event_subtype = pfault->mpfault.event_subtype;
 
         switch (event_subtype) {
+        case MLX5_PFAULT_SUBTYPE_WQE:
+                mlx5_ib_mr_wqe_pfault_handler(qp, pfault);
+                break;
         default:
                 pr_warn("Invalid page fault event subtype: 0x%x\n",
                         event_subtype);
diff --git a/include/linux/mlx5/qp.h b/include/linux/mlx5/qp.h
index 6b1d6f60c7e6..61f7a342d1bf 100644
--- a/include/linux/mlx5/qp.h
+++ b/include/linux/mlx5/qp.h
@@ -193,7 +193,12 @@ struct mlx5_wqe_ctrl_seg {
 };
 
 #define MLX5_WQE_CTRL_DS_MASK 0x3f
+#define MLX5_WQE_CTRL_QPN_MASK 0xffffff00
+#define MLX5_WQE_CTRL_QPN_SHIFT 8
 #define MLX5_WQE_DS_UNITS 16
+#define MLX5_WQE_CTRL_OPCODE_MASK 0xff
+#define MLX5_WQE_CTRL_WQE_INDEX_MASK 0x00ffff00
+#define MLX5_WQE_CTRL_WQE_INDEX_SHIFT 8
 
 struct mlx5_wqe_xrc_seg {
         __be32                  xrc_srqn;
@@ -298,6 +303,8 @@ struct mlx5_wqe_signature_seg {
         u8      rsvd1[11];
 };
 
+#define MLX5_WQE_INLINE_SEG_BYTE_COUNT_MASK 0x3ff
+
 struct mlx5_wqe_inline_seg {
         __be32  byte_count;
 };