[PATCH v3 15/17] IB/mlx5: Handle page faults

Haggai Eran
2014-12-11T15:04:24Z

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-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Shachar Raindel <raindel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Signed-off-by: Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
---
drivers/infiniband/hw/mlx5/odp.c | 408 +++++++++++++++++++++++++++++++++++++++
include/linux/mlx5/qp.h | 7 +
2 files changed, 415 insertions(+)

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;
};