/*
 * Copyright (c) 2013-2015, Mellanox Technologies. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <rdma/ib_umem.h>
#include <rdma/ib_umem_odp.h>
#include <linux/kernel.h>

#include "mlx5_ib.h"
#include "cmd.h"
#include "qp.h"

#include <linux/mlx5/eq.h>

/* Contains the details of a pagefault. */
struct mlx5_pagefault {
        u32                     bytes_committed;
        u32                     token;
        u8                      event_subtype;
        u8                      type;
        union {
                /* Initiator or send message responder pagefault details. */
                struct {
                        /* Received packet size, only valid for responders. */
                        u32     packet_size;
                        /*
                         * Number of resource holding WQE, depends on type.
                         */
                        u32     wq_num;
                        /*
                         * WQE index. Refers to either the send queue or
                         * receive queue, according to event_subtype.
                         */
                        u16     wqe_index;
                } wqe;
                /* RDMA responder pagefault details */
                struct {
                        u32     r_key;
                        /*
                         * Received packet size, minimal size page fault
                         * resolution required for forward progress.
                         */
                        u32     packet_size;
                        u32     rdma_op_len;
                        u64     rdma_va;
                } rdma;
        };

        struct mlx5_ib_pf_eq    *eq;
        struct work_struct      work;
};

#define MAX_PREFETCH_LEN (4*1024*1024U)

/* Timeout in ms to wait for an active mmu notifier to complete when handling
 * a pagefault. */
#define MMU_NOTIFIER_TIMEOUT 1000

#define MLX5_IMR_MTT_BITS (30 - PAGE_SHIFT)
#define MLX5_IMR_MTT_SHIFT (MLX5_IMR_MTT_BITS + PAGE_SHIFT)
#define MLX5_IMR_MTT_ENTRIES BIT_ULL(MLX5_IMR_MTT_BITS)
#define MLX5_IMR_MTT_SIZE BIT_ULL(MLX5_IMR_MTT_SHIFT)
#define MLX5_IMR_MTT_MASK (~(MLX5_IMR_MTT_SIZE - 1))

#define MLX5_KSM_PAGE_SHIFT MLX5_IMR_MTT_SHIFT

static u64 mlx5_imr_ksm_entries;

static void populate_klm(struct mlx5_klm *pklm, size_t idx, size_t nentries,
                        struct mlx5_ib_mr *imr, int flags)
{
        struct mlx5_klm *end = pklm + nentries;

        if (flags & MLX5_IB_UPD_XLT_ZAP) {
                for (; pklm != end; pklm++, idx++) {
                        pklm->bcount = cpu_to_be32(MLX5_IMR_MTT_SIZE);
                        pklm->key = cpu_to_be32(imr->dev->null_mkey);
                        pklm->va = 0;
                }
                return;
        }

        /*
         * The locking here is pretty subtle. Ideally the implicit_children
         * xarray would be protected by the umem_mutex, however that is not
         * possible. Instead this uses a weaker update-then-lock pattern:
         *
         *  srcu_read_lock()
         *    xa_store()
         *    mutex_lock(umem_mutex)
         *     mlx5_ib_update_xlt()
         *    mutex_unlock(umem_mutex)
         *    destroy lkey
         *
         * ie any change the xarray must be followed by the locked update_xlt
         * before destroying.
         *
         * The umem_mutex provides the acquire/release semantic needed to make
         * the xa_store() visible to a racing thread. While SRCU is not
         * technically required, using it gives consistent use of the SRCU
         * locking around the xarray.
         */
        lockdep_assert_held(&to_ib_umem_odp(imr->umem)->umem_mutex);
        lockdep_assert_held(&imr->dev->odp_srcu);

        for (; pklm != end; pklm++, idx++) {
                struct mlx5_ib_mr *mtt = xa_load(&imr->implicit_children, idx);

                pklm->bcount = cpu_to_be32(MLX5_IMR_MTT_SIZE);
                if (mtt) {
                        pklm->key = cpu_to_be32(mtt->ibmr.lkey);
                        pklm->va = cpu_to_be64(idx * MLX5_IMR_MTT_SIZE);
                } else {
                        pklm->key = cpu_to_be32(imr->dev->null_mkey);
                        pklm->va = 0;
                }
        }
}

static u64 umem_dma_to_mtt(dma_addr_t umem_dma)
{
        u64 mtt_entry = umem_dma & ODP_DMA_ADDR_MASK;

        if (umem_dma & ODP_READ_ALLOWED_BIT)
                mtt_entry |= MLX5_IB_MTT_READ;
        if (umem_dma & ODP_WRITE_ALLOWED_BIT)
                mtt_entry |= MLX5_IB_MTT_WRITE;

        return mtt_entry;
}

static void populate_mtt(__be64 *pas, size_t idx, size_t nentries,
                         struct mlx5_ib_mr *mr, int flags)
{
        struct ib_umem_odp *odp = to_ib_umem_odp(mr->umem);
        dma_addr_t pa;
        size_t i;

        if (flags & MLX5_IB_UPD_XLT_ZAP)
                return;

        for (i = 0; i < nentries; i++) {
                pa = odp->dma_list[idx + i];
                pas[i] = cpu_to_be64(umem_dma_to_mtt(pa));
        }
}

void mlx5_odp_populate_xlt(void *xlt, size_t idx, size_t nentries,
                           struct mlx5_ib_mr *mr, int flags)
{
        if (flags & MLX5_IB_UPD_XLT_INDIRECT) {
                populate_klm(xlt, idx, nentries, mr, flags);
        } else {
                populate_mtt(xlt, idx, nentries, mr, flags);
        }
}

static void dma_fence_odp_mr(struct mlx5_ib_mr *mr)
{
        struct ib_umem_odp *odp = to_ib_umem_odp(mr->umem);

        /* Ensure mlx5_ib_invalidate_range() will not touch the MR any more */
        mutex_lock(&odp->umem_mutex);
        if (odp->npages) {
                mlx5_mr_cache_invalidate(mr);
                ib_umem_odp_unmap_dma_pages(odp, ib_umem_start(odp),
                                            ib_umem_end(odp));
                WARN_ON(odp->npages);
        }
        odp->private = NULL;
        mutex_unlock(&odp->umem_mutex);

        if (!mr->cache_ent) {
                mlx5_core_destroy_mkey(mr->dev->mdev, &mr->mmkey);
                WARN_ON(mr->descs);
        }
}

/*
 * This must be called after the mr has been removed from implicit_children
 * and the SRCU synchronized.  NOTE: The MR does not necessarily have to be
 * empty here, parallel page faults could have raced with the free process and
 * added pages to it.
 */
static void free_implicit_child_mr(struct mlx5_ib_mr *mr, bool need_imr_xlt)
{
        struct mlx5_ib_mr *imr = mr->parent;
        struct ib_umem_odp *odp_imr = to_ib_umem_odp(imr->umem);
        struct ib_umem_odp *odp = to_ib_umem_odp(mr->umem);
        unsigned long idx = ib_umem_start(odp) >> MLX5_IMR_MTT_SHIFT;
        int srcu_key;

        /* implicit_child_mr's are not allowed to have deferred work */
        WARN_ON(atomic_read(&mr->num_deferred_work));

        if (need_imr_xlt) {
                srcu_key = srcu_read_lock(&mr->dev->odp_srcu);
                mutex_lock(&odp_imr->umem_mutex);
                mlx5_ib_update_xlt(mr->parent, idx, 1, 0,
                                   MLX5_IB_UPD_XLT_INDIRECT |
                                   MLX5_IB_UPD_XLT_ATOMIC);
                mutex_unlock(&odp_imr->umem_mutex);
                srcu_read_unlock(&mr->dev->odp_srcu, srcu_key);
        }

        dma_fence_odp_mr(mr);

        mr->parent = NULL;
        mlx5_mr_cache_free(mr->dev, mr);
        ib_umem_odp_release(odp);
        if (atomic_dec_and_test(&imr->num_deferred_work))
                wake_up(&imr->q_deferred_work);
}

static void free_implicit_child_mr_work(struct work_struct *work)
{
        struct mlx5_ib_mr *mr =
                container_of(work, struct mlx5_ib_mr, odp_destroy.work);

        free_implicit_child_mr(mr, true);
}

static void free_implicit_child_mr_rcu(struct rcu_head *head)
{
        struct mlx5_ib_mr *mr =
                container_of(head, struct mlx5_ib_mr, odp_destroy.rcu);

        /* Freeing a MR is a sleeping operation, so bounce to a work queue */
        INIT_WORK(&mr->odp_destroy.work, free_implicit_child_mr_work);
        queue_work(system_unbound_wq, &mr->odp_destroy.work);
}

static void destroy_unused_implicit_child_mr(struct mlx5_ib_mr *mr)
{
        struct ib_umem_odp *odp = to_ib_umem_odp(mr->umem);
        unsigned long idx = ib_umem_start(odp) >> MLX5_IMR_MTT_SHIFT;
        struct mlx5_ib_mr *imr = mr->parent;

        xa_lock(&imr->implicit_children);
        /*
         * This can race with mlx5_ib_free_implicit_mr(), the first one to
         * reach the xa lock wins the race and destroys the MR.
         */
        if (__xa_cmpxchg(&imr->implicit_children, idx, mr, NULL, GFP_ATOMIC) !=
            mr)
                goto out_unlock;

        atomic_inc(&imr->num_deferred_work);
        call_srcu(&mr->dev->odp_srcu, &mr->odp_destroy.rcu,
                  free_implicit_child_mr_rcu);

out_unlock:
        xa_unlock(&imr->implicit_children);
}

static bool mlx5_ib_invalidate_range(struct mmu_interval_notifier *mni,
                                     const struct mmu_notifier_range *range,
                                     unsigned long cur_seq)
{
        struct ib_umem_odp *umem_odp =
                container_of(mni, struct ib_umem_odp, notifier);
        struct mlx5_ib_mr *mr;
        const u64 umr_block_mask = (MLX5_UMR_MTT_ALIGNMENT /
                                    sizeof(struct mlx5_mtt)) - 1;
        u64 idx = 0, blk_start_idx = 0;
        u64 invalidations = 0;
        unsigned long start;
        unsigned long end;
        int in_block = 0;
        u64 addr;

        if (!mmu_notifier_range_blockable(range))
                return false;

        mutex_lock(&umem_odp->umem_mutex);
        mmu_interval_set_seq(mni, cur_seq);
        /*
         * If npages is zero then umem_odp->private may not be setup yet. This
         * does not complete until after the first page is mapped for DMA.
         */
        if (!umem_odp->npages)
                goto out;
        mr = umem_odp->private;

        start = max_t(u64, ib_umem_start(umem_odp), range->start);
        end = min_t(u64, ib_umem_end(umem_odp), range->end);

        /*
         * Iteration one - zap the HW's MTTs. The notifiers_count ensures that
         * while we are doing the invalidation, no page fault will attempt to
         * overwrite the same MTTs.  Concurent invalidations might race us,
         * but they will write 0s as well, so no difference in the end result.
         */
        for (addr = start; addr < end; addr += BIT(umem_odp->page_shift)) {
                idx = (addr - ib_umem_start(umem_odp)) >> umem_odp->page_shift;
                /*
                 * Strive to write the MTTs in chunks, but avoid overwriting
                 * non-existing MTTs. The huristic here can be improved to
                 * estimate the cost of another UMR vs. the cost of bigger
                 * UMR.
                 */
                if (umem_odp->dma_list[idx] &
                    (ODP_READ_ALLOWED_BIT | ODP_WRITE_ALLOWED_BIT)) {
                        if (!in_block) {
                                blk_start_idx = idx;
                                in_block = 1;
                        }

                        /* Count page invalidations */
                        invalidations += idx - blk_start_idx + 1;
                } else {
                        u64 umr_offset = idx & umr_block_mask;

                        if (in_block && umr_offset == 0) {
                                mlx5_ib_update_xlt(mr, blk_start_idx,
                                                   idx - blk_start_idx, 0,
                                                   MLX5_IB_UPD_XLT_ZAP |
                                                   MLX5_IB_UPD_XLT_ATOMIC);
                                in_block = 0;
                        }
                }
        }
        if (in_block)
                mlx5_ib_update_xlt(mr, blk_start_idx,
                                   idx - blk_start_idx + 1, 0,
                                   MLX5_IB_UPD_XLT_ZAP |
                                   MLX5_IB_UPD_XLT_ATOMIC);

        mlx5_update_odp_stats(mr, invalidations, invalidations);

        /*
         * We are now sure that the device will not access the
         * memory. We can safely unmap it, and mark it as dirty if
         * needed.
         */

        ib_umem_odp_unmap_dma_pages(umem_odp, start, end);

        if (unlikely(!umem_odp->npages && mr->parent))
                destroy_unused_implicit_child_mr(mr);
out:
        mutex_unlock(&umem_odp->umem_mutex);
        return true;
}

const struct mmu_interval_notifier_ops mlx5_mn_ops = {
        .invalidate = mlx5_ib_invalidate_range,
};

void mlx5_ib_internal_fill_odp_caps(struct mlx5_ib_dev *dev)
{
        struct ib_odp_caps *caps = &dev->odp_caps;

        memset(caps, 0, sizeof(*caps));

        if (!MLX5_CAP_GEN(dev->mdev, pg) ||
            !mlx5_ib_can_use_umr(dev, true, 0))
                return;

        caps->general_caps = IB_ODP_SUPPORT;

        if (MLX5_CAP_GEN(dev->mdev, umr_extended_translation_offset))
                dev->odp_max_size = U64_MAX;
        else
                dev->odp_max_size = BIT_ULL(MLX5_MAX_UMR_SHIFT + PAGE_SHIFT);

        if (MLX5_CAP_ODP(dev->mdev, ud_odp_caps.send))
                caps->per_transport_caps.ud_odp_caps |= IB_ODP_SUPPORT_SEND;

        if (MLX5_CAP_ODP(dev->mdev, ud_odp_caps.srq_receive))
                caps->per_transport_caps.ud_odp_caps |= IB_ODP_SUPPORT_SRQ_RECV;

        if (MLX5_CAP_ODP(dev->mdev, rc_odp_caps.send))
                caps->per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_SEND;

        if (MLX5_CAP_ODP(dev->mdev, rc_odp_caps.receive))
                caps->per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_RECV;

        if (MLX5_CAP_ODP(dev->mdev, rc_odp_caps.write))
                caps->per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_WRITE;

        if (MLX5_CAP_ODP(dev->mdev, rc_odp_caps.read))
                caps->per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_READ;

        if (MLX5_CAP_ODP(dev->mdev, rc_odp_caps.atomic))
                caps->per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_ATOMIC;

        if (MLX5_CAP_ODP(dev->mdev, rc_odp_caps.srq_receive))
                caps->per_transport_caps.rc_odp_caps |= IB_ODP_SUPPORT_SRQ_RECV;

        if (MLX5_CAP_ODP(dev->mdev, xrc_odp_caps.send))
                caps->per_transport_caps.xrc_odp_caps |= IB_ODP_SUPPORT_SEND;

        if (MLX5_CAP_ODP(dev->mdev, xrc_odp_caps.receive))
                caps->per_transport_caps.xrc_odp_caps |= IB_ODP_SUPPORT_RECV;

        if (MLX5_CAP_ODP(dev->mdev, xrc_odp_caps.write))
                caps->per_transport_caps.xrc_odp_caps |= IB_ODP_SUPPORT_WRITE;

        if (MLX5_CAP_ODP(dev->mdev, xrc_odp_caps.read))
                caps->per_transport_caps.xrc_odp_caps |= IB_ODP_SUPPORT_READ;

        if (MLX5_CAP_ODP(dev->mdev, xrc_odp_caps.atomic))
                caps->per_transport_caps.xrc_odp_caps |= IB_ODP_SUPPORT_ATOMIC;

        if (MLX5_CAP_ODP(dev->mdev, xrc_odp_caps.srq_receive))
                caps->per_transport_caps.xrc_odp_caps |= IB_ODP_SUPPORT_SRQ_RECV;

        if (MLX5_CAP_GEN(dev->mdev, fixed_buffer_size) &&
            MLX5_CAP_GEN(dev->mdev, null_mkey) &&
            MLX5_CAP_GEN(dev->mdev, umr_extended_translation_offset) &&
            !MLX5_CAP_GEN(dev->mdev, umr_indirect_mkey_disabled))
                caps->general_caps |= IB_ODP_SUPPORT_IMPLICIT;
}

static void mlx5_ib_page_fault_resume(struct mlx5_ib_dev *dev,
                                      struct mlx5_pagefault *pfault,
                                      int error)
{
        int wq_num = pfault->event_subtype == MLX5_PFAULT_SUBTYPE_WQE ?
                     pfault->wqe.wq_num : pfault->token;
        u32 in[MLX5_ST_SZ_DW(page_fault_resume_in)] = {};
        int err;

        MLX5_SET(page_fault_resume_in, in, opcode, MLX5_CMD_OP_PAGE_FAULT_RESUME);
        MLX5_SET(page_fault_resume_in, in, page_fault_type, pfault->type);
        MLX5_SET(page_fault_resume_in, in, token, pfault->token);
        MLX5_SET(page_fault_resume_in, in, wq_number, wq_num);
        MLX5_SET(page_fault_resume_in, in, error, !!error);

        err = mlx5_cmd_exec_in(dev->mdev, page_fault_resume, in);
        if (err)
                mlx5_ib_err(dev, "Failed to resolve the page fault on WQ 0x%x err %d\n",
                            wq_num, err);
}

static struct mlx5_ib_mr *implicit_get_child_mr(struct mlx5_ib_mr *imr,
                                                unsigned long idx)
{
        struct ib_umem_odp *odp;
        struct mlx5_ib_mr *mr;
        struct mlx5_ib_mr *ret;
        int err;

        odp = ib_umem_odp_alloc_child(to_ib_umem_odp(imr->umem),
                                      idx * MLX5_IMR_MTT_SIZE,
                                      MLX5_IMR_MTT_SIZE, &mlx5_mn_ops);
        if (IS_ERR(odp))
                return ERR_CAST(odp);

        ret = mr = mlx5_mr_cache_alloc(imr->dev, MLX5_IMR_MTT_CACHE_ENTRY);
        if (IS_ERR(mr))
                goto out_umem;

        mr->ibmr.pd = imr->ibmr.pd;
        mr->access_flags = imr->access_flags;
        mr->umem = &odp->umem;
        mr->ibmr.lkey = mr->mmkey.key;
        mr->ibmr.rkey = mr->mmkey.key;
        mr->mmkey.iova = idx * MLX5_IMR_MTT_SIZE;
        mr->parent = imr;
        odp->private = mr;

        err = mlx5_ib_update_xlt(mr, 0,
                                 MLX5_IMR_MTT_ENTRIES,
                                 PAGE_SHIFT,
                                 MLX5_IB_UPD_XLT_ZAP |
                                 MLX5_IB_UPD_XLT_ENABLE);
        if (err) {
                ret = ERR_PTR(err);
                goto out_mr;
        }

        /*
         * Once the store to either xarray completes any error unwind has to
         * use synchronize_srcu(). Avoid this with xa_reserve()
         */
        ret = xa_cmpxchg(&imr->implicit_children, idx, NULL, mr,
                         GFP_KERNEL);
        if (unlikely(ret)) {
                if (xa_is_err(ret)) {
                        ret = ERR_PTR(xa_err(ret));
                        goto out_mr;
                }
                /*
                 * Another thread beat us to creating the child mr, use
                 * theirs.
                 */
                goto out_mr;
        }

        mlx5_ib_dbg(imr->dev, "key %x mr %p\n", mr->mmkey.key, mr);
        return mr;

out_mr:
        mlx5_mr_cache_free(imr->dev, mr);
out_umem:
        ib_umem_odp_release(odp);
        return ret;
}

struct mlx5_ib_mr *mlx5_ib_alloc_implicit_mr(struct mlx5_ib_pd *pd,
                                             struct ib_udata *udata,
                                             int access_flags)
{
        struct mlx5_ib_dev *dev = to_mdev(pd->ibpd.device);
        struct ib_umem_odp *umem_odp;
        struct mlx5_ib_mr *imr;
        int err;

        umem_odp = ib_umem_odp_alloc_implicit(&dev->ib_dev, access_flags);
        if (IS_ERR(umem_odp))
                return ERR_CAST(umem_odp);

        imr = mlx5_mr_cache_alloc(dev, MLX5_IMR_KSM_CACHE_ENTRY);
        if (IS_ERR(imr)) {
                err = PTR_ERR(imr);
                goto out_umem;
        }

        imr->ibmr.pd = &pd->ibpd;
        imr->access_flags = access_flags;
        imr->mmkey.iova = 0;
        imr->umem = &umem_odp->umem;
        imr->ibmr.lkey = imr->mmkey.key;
        imr->ibmr.rkey = imr->mmkey.key;
        imr->umem = &umem_odp->umem;
        imr->is_odp_implicit = true;
        atomic_set(&imr->num_deferred_work, 0);
        init_waitqueue_head(&imr->q_deferred_work);
        xa_init(&imr->implicit_children);

        err = mlx5_ib_update_xlt(imr, 0,
                                 mlx5_imr_ksm_entries,
                                 MLX5_KSM_PAGE_SHIFT,
                                 MLX5_IB_UPD_XLT_INDIRECT |
                                 MLX5_IB_UPD_XLT_ZAP |
                                 MLX5_IB_UPD_XLT_ENABLE);
        if (err)
                goto out_mr;

        err = xa_err(xa_store(&dev->odp_mkeys, mlx5_base_mkey(imr->mmkey.key),
                              &imr->mmkey, GFP_KERNEL));
        if (err)
                goto out_mr;

        mlx5_ib_dbg(dev, "key %x mr %p\n", imr->mmkey.key, imr);
        return imr;
out_mr:
        mlx5_ib_err(dev, "Failed to register MKEY %d\n", err);
        mlx5_mr_cache_free(dev, imr);
out_umem:
        ib_umem_odp_release(umem_odp);
        return ERR_PTR(err);
}

void mlx5_ib_free_implicit_mr(struct mlx5_ib_mr *imr)
{
        struct ib_umem_odp *odp_imr = to_ib_umem_odp(imr->umem);
        struct mlx5_ib_dev *dev = imr->dev;
        struct list_head destroy_list;
        struct mlx5_ib_mr *mtt;
        struct mlx5_ib_mr *tmp;
        unsigned long idx;

        INIT_LIST_HEAD(&destroy_list);

        xa_erase(&dev->odp_mkeys, mlx5_base_mkey(imr->mmkey.key));
        /*
         * This stops the SRCU protected page fault path from touching either
         * the imr or any children. The page fault path can only reach the
         * children xarray via the imr.
         */
        synchronize_srcu(&dev->odp_srcu);

        /*
         * All work on the prefetch list must be completed, xa_erase() prevented
         * new work from being created.
         */
        wait_event(imr->q_deferred_work, !atomic_read(&imr->num_deferred_work));

        /*
         * At this point it is forbidden for any other thread to enter
         * pagefault_mr() on this imr. It is already forbidden to call
         * pagefault_mr() on an implicit child. Due to this additions to
         * implicit_children are prevented.
         */

        /*
         * Block destroy_unused_implicit_child_mr() from incrementing
         * num_deferred_work.
         */
        xa_lock(&imr->implicit_children);
        xa_for_each (&imr->implicit_children, idx, mtt) {
                __xa_erase(&imr->implicit_children, idx);
                list_add(&mtt->odp_destroy.elm, &destroy_list);
        }
        xa_unlock(&imr->implicit_children);

        /*
         * Wait for any concurrent destroy_unused_implicit_child_mr() to
         * complete.
         */
        wait_event(imr->q_deferred_work, !atomic_read(&imr->num_deferred_work));

        /*
         * Fence the imr before we destroy the children. This allows us to
         * skip updating the XLT of the imr during destroy of the child mkey
         * the imr points to.
         */
        mlx5_mr_cache_invalidate(imr);

        list_for_each_entry_safe (mtt, tmp, &destroy_list, odp_destroy.elm)
                free_implicit_child_mr(mtt, false);

        mlx5_mr_cache_free(dev, imr);
        ib_umem_odp_release(odp_imr);
}

/**
 * mlx5_ib_fence_odp_mr - Stop all access to the ODP MR
 * @mr: to fence
 *
 * On return no parallel threads will be touching this MR and no DMA will be
 * active.
 */
void mlx5_ib_fence_odp_mr(struct mlx5_ib_mr *mr)
{
        /* Prevent new page faults and prefetch requests from succeeding */
        xa_erase(&mr->dev->odp_mkeys, mlx5_base_mkey(mr->mmkey.key));

        /* Wait for all running page-fault handlers to finish. */
        synchronize_srcu(&mr->dev->odp_srcu);

        wait_event(mr->q_deferred_work, !atomic_read(&mr->num_deferred_work));

        dma_fence_odp_mr(mr);
}

#define MLX5_PF_FLAGS_DOWNGRADE BIT(1)
static int pagefault_real_mr(struct mlx5_ib_mr *mr, struct ib_umem_odp *odp,
                             u64 user_va, size_t bcnt, u32 *bytes_mapped,
                             u32 flags)
{
        int page_shift, ret, np;
        bool downgrade = flags & MLX5_PF_FLAGS_DOWNGRADE;
        unsigned long current_seq;
        u64 access_mask;
        u64 start_idx;

        page_shift = odp->page_shift;
        start_idx = (user_va - ib_umem_start(odp)) >> page_shift;
        access_mask = ODP_READ_ALLOWED_BIT;

        if (odp->umem.writable && !downgrade)
                access_mask |= ODP_WRITE_ALLOWED_BIT;

        current_seq = mmu_interval_read_begin(&odp->notifier);

        np = ib_umem_odp_map_dma_pages(odp, user_va, bcnt, access_mask,
                                       current_seq);
        if (np < 0)
                return np;

        mutex_lock(&odp->umem_mutex);
        if (!mmu_interval_read_retry(&odp->notifier, current_seq)) {
                /*
                 * 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_xlt(mr, start_idx, np,
                                         page_shift, MLX5_IB_UPD_XLT_ATOMIC);
        } else {
                ret = -EAGAIN;
        }
        mutex_unlock(&odp->umem_mutex);

        if (ret < 0) {
                if (ret != -EAGAIN)
                        mlx5_ib_err(mr->dev,
                                    "Failed to update mkey page tables\n");
                goto out;
        }

        if (bytes_mapped) {
                u32 new_mappings = (np << page_shift) -
                        (user_va - round_down(user_va, 1 << page_shift));

                *bytes_mapped += min_t(u32, new_mappings, bcnt);
        }

        return np << (page_shift - PAGE_SHIFT);

out:
        return ret;
}

static int pagefault_implicit_mr(struct mlx5_ib_mr *imr,
                                 struct ib_umem_odp *odp_imr, u64 user_va,
                                 size_t bcnt, u32 *bytes_mapped, u32 flags)
{
        unsigned long end_idx = (user_va + bcnt - 1) >> MLX5_IMR_MTT_SHIFT;
        unsigned long upd_start_idx = end_idx + 1;
        unsigned long upd_len = 0;
        unsigned long npages = 0;
        int err;
        int ret;

        if (unlikely(user_va >= mlx5_imr_ksm_entries * MLX5_IMR_MTT_SIZE ||
                     mlx5_imr_ksm_entries * MLX5_IMR_MTT_SIZE - user_va < bcnt))
                return -EFAULT;

        /* Fault each child mr that intersects with our interval. */
        while (bcnt) {
                unsigned long idx = user_va >> MLX5_IMR_MTT_SHIFT;
                struct ib_umem_odp *umem_odp;
                struct mlx5_ib_mr *mtt;
                u64 len;

                mtt = xa_load(&imr->implicit_children, idx);
                if (unlikely(!mtt)) {
                        mtt = implicit_get_child_mr(imr, idx);
                        if (IS_ERR(mtt)) {
                                ret = PTR_ERR(mtt);
                                goto out;
                        }
                        upd_start_idx = min(upd_start_idx, idx);
                        upd_len = idx - upd_start_idx + 1;
                }

                umem_odp = to_ib_umem_odp(mtt->umem);
                len = min_t(u64, user_va + bcnt, ib_umem_end(umem_odp)) -
                      user_va;

                ret = pagefault_real_mr(mtt, umem_odp, user_va, len,
                                        bytes_mapped, flags);
                if (ret < 0)
                        goto out;
                user_va += len;
                bcnt -= len;
                npages += ret;
        }

        ret = npages;

        /*
         * Any time the implicit_children are changed we must perform an
         * update of the xlt before exiting to ensure the HW and the
         * implicit_children remains synchronized.
         */
out:
        if (likely(!upd_len))
                return ret;

        /*
         * Notice this is not strictly ordered right, the KSM is updated after
         * the implicit_children is updated, so a parallel page fault could
         * see a MR that is not yet visible in the KSM.  This is similar to a
         * parallel page fault seeing a MR that is being concurrently removed
         * from the KSM. Both of these improbable situations are resolved
         * safely by resuming the HW and then taking another page fault. The
         * next pagefault handler will see the new information.
         */
        mutex_lock(&odp_imr->umem_mutex);
        err = mlx5_ib_update_xlt(imr, upd_start_idx, upd_len, 0,
                                 MLX5_IB_UPD_XLT_INDIRECT |
                                         MLX5_IB_UPD_XLT_ATOMIC);
        mutex_unlock(&odp_imr->umem_mutex);
        if (err) {
                mlx5_ib_err(imr->dev, "Failed to update PAS\n");
                return err;
        }
        return ret;
}

/*
 * Returns:
 *  -EFAULT: The io_virt->bcnt is not within the MR, it covers pages that are
 *           not accessible, or the MR is no longer valid.
 *  -EAGAIN/-ENOMEM: The operation should be retried
 *
 *  -EINVAL/others: General internal malfunction
 *  >0: Number of pages mapped
 */
static int pagefault_mr(struct mlx5_ib_mr *mr, u64 io_virt, size_t bcnt,
                        u32 *bytes_mapped, u32 flags)
{
        struct ib_umem_odp *odp = to_ib_umem_odp(mr->umem);

        lockdep_assert_held(&mr->dev->odp_srcu);
        if (unlikely(io_virt < mr->mmkey.iova))
                return -EFAULT;

        if (!odp->is_implicit_odp) {
                u64 user_va;

                if (check_add_overflow(io_virt - mr->mmkey.iova,
                                       (u64)odp->umem.address, &user_va))
                        return -EFAULT;
                if (unlikely(user_va >= ib_umem_end(odp) ||
                             ib_umem_end(odp) - user_va < bcnt))
                        return -EFAULT;
                return pagefault_real_mr(mr, odp, user_va, bcnt, bytes_mapped,
                                         flags);
        }
        return pagefault_implicit_mr(mr, odp, io_virt, bcnt, bytes_mapped,
                                     flags);
}

struct pf_frame {
        struct pf_frame *next;
        u32 key;
        u64 io_virt;
        size_t bcnt;
        int depth;
};

static bool mkey_is_eq(struct mlx5_core_mkey *mmkey, u32 key)
{
        if (!mmkey)
                return false;
        if (mmkey->type == MLX5_MKEY_MW)
                return mlx5_base_mkey(mmkey->key) == mlx5_base_mkey(key);
        return mmkey->key == key;
}

static int get_indirect_num_descs(struct mlx5_core_mkey *mmkey)
{
        struct mlx5_ib_mw *mw;
        struct mlx5_ib_devx_mr *devx_mr;

        if (mmkey->type == MLX5_MKEY_MW) {
                mw = container_of(mmkey, struct mlx5_ib_mw, mmkey);
                return mw->ndescs;
        }

        devx_mr = container_of(mmkey, struct mlx5_ib_devx_mr,
                               mmkey);
        return devx_mr->ndescs;
}

/*
 * Handle a single data segment in a page-fault WQE or RDMA region.
 *
 * Returns number of OS pages retrieved on success. The caller may 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.
 */
static int pagefault_single_data_segment(struct mlx5_ib_dev *dev,
                                         struct ib_pd *pd, u32 key,
                                         u64 io_virt, size_t bcnt,
                                         u32 *bytes_committed,
                                         u32 *bytes_mapped)
{
        int npages = 0, srcu_key, ret, i, outlen, cur_outlen = 0, depth = 0;
        struct pf_frame *head = NULL, *frame;
        struct mlx5_core_mkey *mmkey;
        struct mlx5_ib_mr *mr;
        struct mlx5_klm *pklm;
        u32 *out = NULL;
        size_t offset;
        int ndescs;

        srcu_key = srcu_read_lock(&dev->odp_srcu);

        io_virt += *bytes_committed;
        bcnt -= *bytes_committed;

next_mr:
        mmkey = xa_load(&dev->odp_mkeys, mlx5_base_mkey(key));
        if (!mmkey) {
                mlx5_ib_dbg(
                        dev,
                        "skipping non ODP MR (lkey=0x%06x) in page fault handler.\n",
                        key);
                if (bytes_mapped)
                        *bytes_mapped += bcnt;
                /*
                 * The user could specify a SGL with multiple lkeys and only
                 * some of them are ODP. Treat the non-ODP ones as fully
                 * faulted.
                 */
                ret = 0;
                goto srcu_unlock;
        }
        if (!mkey_is_eq(mmkey, key)) {
                mlx5_ib_dbg(dev, "failed to find mkey %x\n", key);
                ret = -EFAULT;
                goto srcu_unlock;
        }

        switch (mmkey->type) {
        case MLX5_MKEY_MR:
                mr = container_of(mmkey, struct mlx5_ib_mr, mmkey);

                ret = pagefault_mr(mr, io_virt, bcnt, bytes_mapped, 0);
                if (ret < 0)
                        goto srcu_unlock;

                mlx5_update_odp_stats(mr, faults, ret);

                npages += ret;
                ret = 0;
                break;

        case MLX5_MKEY_MW:
        case MLX5_MKEY_INDIRECT_DEVX:
                ndescs = get_indirect_num_descs(mmkey);

                if (depth >= MLX5_CAP_GEN(dev->mdev, max_indirection)) {
                        mlx5_ib_dbg(dev, "indirection level exceeded\n");
                        ret = -EFAULT;
                        goto srcu_unlock;
                }

                outlen = MLX5_ST_SZ_BYTES(query_mkey_out) +
                        sizeof(*pklm) * (ndescs - 2);

                if (outlen > cur_outlen) {
                        kfree(out);
                        out = kzalloc(outlen, GFP_KERNEL);
                        if (!out) {
                                ret = -ENOMEM;
                                goto srcu_unlock;
                        }
                        cur_outlen = outlen;
                }

                pklm = (struct mlx5_klm *)MLX5_ADDR_OF(query_mkey_out, out,
                                                       bsf0_klm0_pas_mtt0_1);

                ret = mlx5_core_query_mkey(dev->mdev, mmkey, out, outlen);
                if (ret)
                        goto srcu_unlock;

                offset = io_virt - MLX5_GET64(query_mkey_out, out,
                                              memory_key_mkey_entry.start_addr);

                for (i = 0; bcnt && i < ndescs; i++, pklm++) {
                        if (offset >= be32_to_cpu(pklm->bcount)) {
                                offset -= be32_to_cpu(pklm->bcount);
                                continue;
                        }

                        frame = kzalloc(sizeof(*frame), GFP_KERNEL);
                        if (!frame) {
                                ret = -ENOMEM;
                                goto srcu_unlock;
                        }

                        frame->key = be32_to_cpu(pklm->key);
                        frame->io_virt = be64_to_cpu(pklm->va) + offset;
                        frame->bcnt = min_t(size_t, bcnt,
                                            be32_to_cpu(pklm->bcount) - offset);
                        frame->depth = depth + 1;
                        frame->next = head;
                        head = frame;

                        bcnt -= frame->bcnt;
                        offset = 0;
                }
                break;

        default:
                mlx5_ib_dbg(dev, "wrong mkey type %d\n", mmkey->type);
                ret = -EFAULT;
                goto srcu_unlock;

        }

        if (head) {
                frame = head;
                head = frame->next;

                key = frame->key;
                io_virt = frame->io_virt;
                bcnt = frame->bcnt;
                depth = frame->depth;
                kfree(frame);

                goto next_mr;
        }

srcu_unlock:
        while (head) {
                frame = head;
                head = frame->next;
                kfree(frame);
        }
        kfree(out);

        srcu_read_unlock(&dev->odp_srcu, srcu_key);
        *bytes_committed = 0;
        return ret ? ret : npages;
}

/**
 * Parse a series of data segments for page fault handling.
 *
 * @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_dev *dev,
                                   struct mlx5_pagefault *pfault,
                                   void *wqe,
                                   void *wqe_end, u32 *bytes_mapped,
                                   u32 *total_wqe_bytes, bool receive_queue)
{
        int ret = 0, npages = 0;
        u64 io_virt;
        u32 key;
        u32 byte_count;
        size_t bcnt;
        int inline_segment;

        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->bytes_committed);
                }

                /* A zero length data segment designates a length of 2GB. */
                if (bcnt == 0)
                        bcnt = 1U << 31;

                if (inline_segment || bcnt <= pfault->bytes_committed) {
                        pfault->bytes_committed -=
                                min_t(size_t, bcnt,
                                      pfault->bytes_committed);
                        continue;
                }

                ret = pagefault_single_data_segment(dev, NULL, key,
                                                    io_virt, bcnt,
                                                    &pfault->bytes_committed,
                                                    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_dev *dev, struct mlx5_pagefault *pfault,
        struct mlx5_ib_qp *qp, void **wqe, void **wqe_end, int wqe_length)
{
        struct mlx5_wqe_ctrl_seg *ctrl = *wqe;
        u16 wqe_index = pfault->wqe.wqe_index;
        struct mlx5_base_av *av;
        unsigned ds, opcode;
        u32 qpn = qp->trans_qp.base.mqp.qpn;

        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, qpn);
                return -EFAULT;
        }

        *wqe_end = *wqe + ds * MLX5_WQE_DS_UNITS;
        *wqe += sizeof(*ctrl);

        opcode = be32_to_cpu(ctrl->opmod_idx_opcode) &
                 MLX5_WQE_CTRL_OPCODE_MASK;

        if (qp->ibqp.qp_type == IB_QPT_XRC_INI)
                *wqe += sizeof(struct mlx5_wqe_xrc_seg);

        if (qp->type == IB_QPT_UD || qp->type == MLX5_IB_QPT_DCI) {
                av = *wqe;
                if (av->dqp_dct & cpu_to_be32(MLX5_EXTENDED_UD_AV))
                        *wqe += sizeof(struct mlx5_av);
                else
                        *wqe += sizeof(struct mlx5_base_av);
        }

        switch (opcode) {
        case MLX5_OPCODE_RDMA_WRITE:
        case MLX5_OPCODE_RDMA_WRITE_IMM:
        case MLX5_OPCODE_RDMA_READ:
                *wqe += sizeof(struct mlx5_wqe_raddr_seg);
                break;
        case MLX5_OPCODE_ATOMIC_CS:
        case MLX5_OPCODE_ATOMIC_FA:
                *wqe += sizeof(struct mlx5_wqe_raddr_seg);
                *wqe += sizeof(struct mlx5_wqe_atomic_seg);
                break;
        }

        return 0;
}

/*
 * Parse responder WQE and set wqe_end to the end of the WQE.
 */
static int mlx5_ib_mr_responder_pfault_handler_srq(struct mlx5_ib_dev *dev,
                                                   struct mlx5_ib_srq *srq,
                                                   void **wqe, void **wqe_end,
                                                   int wqe_length)
{
        int wqe_size = 1 << srq->msrq.wqe_shift;

        if (wqe_size > wqe_length) {
                mlx5_ib_err(dev, "Couldn't read all of the receive WQE's content\n");
                return -EFAULT;
        }

        *wqe_end = *wqe + wqe_size;
        *wqe += sizeof(struct mlx5_wqe_srq_next_seg);

        return 0;
}

static int mlx5_ib_mr_responder_pfault_handler_rq(struct mlx5_ib_dev *dev,
                                                  struct mlx5_ib_qp *qp,
                                                  void *wqe, void **wqe_end,
                                                  int wqe_length)
{
        struct mlx5_ib_wq *wq = &qp->rq;
        int wqe_size = 1 << wq->wqe_shift;

        if (qp->flags_en & MLX5_QP_FLAG_SIGNATURE) {
                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;
        }

        *wqe_end = wqe + wqe_size;

        return 0;
}

static inline struct mlx5_core_rsc_common *odp_get_rsc(struct mlx5_ib_dev *dev,
                                                       u32 wq_num, int pf_type)
{
        struct mlx5_core_rsc_common *common = NULL;
        struct mlx5_core_srq *srq;

        switch (pf_type) {
        case MLX5_WQE_PF_TYPE_RMP:
                srq = mlx5_cmd_get_srq(dev, wq_num);
                if (srq)
                        common = &srq->common;
                break;
        case MLX5_WQE_PF_TYPE_REQ_SEND_OR_WRITE:
        case MLX5_WQE_PF_TYPE_RESP:
        case MLX5_WQE_PF_TYPE_REQ_READ_OR_ATOMIC:
                common = mlx5_core_res_hold(dev, wq_num, MLX5_RES_QP);
                break;
        default:
                break;
        }

        return common;
}

static inline struct mlx5_ib_qp *res_to_qp(struct mlx5_core_rsc_common *res)
{
        struct mlx5_core_qp *mqp = (struct mlx5_core_qp *)res;

        return to_mibqp(mqp);
}

static inline struct mlx5_ib_srq *res_to_srq(struct mlx5_core_rsc_common *res)
{
        struct mlx5_core_srq *msrq =
                container_of(res, struct mlx5_core_srq, common);

        return to_mibsrq(msrq);
}

static void mlx5_ib_mr_wqe_pfault_handler(struct mlx5_ib_dev *dev,
                                          struct mlx5_pagefault *pfault)
{
        bool sq = pfault->type & MLX5_PFAULT_REQUESTOR;
        u16 wqe_index = pfault->wqe.wqe_index;
        void *wqe, *wqe_start = NULL, *wqe_end = NULL;
        u32 bytes_mapped, total_wqe_bytes;
        struct mlx5_core_rsc_common *res;
        int resume_with_error = 1;
        struct mlx5_ib_qp *qp;
        size_t bytes_copied;
        int ret = 0;

        res = odp_get_rsc(dev, pfault->wqe.wq_num, pfault->type);
        if (!res) {
                mlx5_ib_dbg(dev, "wqe page fault for missing resource %d\n", pfault->wqe.wq_num);
                return;
        }

        if (res->res != MLX5_RES_QP && res->res != MLX5_RES_SRQ &&
            res->res != MLX5_RES_XSRQ) {
                mlx5_ib_err(dev, "wqe page fault for unsupported type %d\n",
                            pfault->type);
                goto resolve_page_fault;
        }

        wqe_start = (void *)__get_free_page(GFP_KERNEL);
        if (!wqe_start) {
                mlx5_ib_err(dev, "Error allocating memory for IO page fault handling.\n");
                goto resolve_page_fault;
        }

        wqe = wqe_start;
        qp = (res->res == MLX5_RES_QP) ? res_to_qp(res) : NULL;
        if (qp && sq) {
                ret = mlx5_ib_read_wqe_sq(qp, wqe_index, wqe, PAGE_SIZE,
                                          &bytes_copied);
                if (ret)
                        goto read_user;
                ret = mlx5_ib_mr_initiator_pfault_handler(
                        dev, pfault, qp, &wqe, &wqe_end, bytes_copied);
        } else if (qp && !sq) {
                ret = mlx5_ib_read_wqe_rq(qp, wqe_index, wqe, PAGE_SIZE,
                                          &bytes_copied);
                if (ret)
                        goto read_user;
                ret = mlx5_ib_mr_responder_pfault_handler_rq(
                        dev, qp, wqe, &wqe_end, bytes_copied);
        } else if (!qp) {
                struct mlx5_ib_srq *srq = res_to_srq(res);

                ret = mlx5_ib_read_wqe_srq(srq, wqe_index, wqe, PAGE_SIZE,
                                           &bytes_copied);
                if (ret)
                        goto read_user;
                ret = mlx5_ib_mr_responder_pfault_handler_srq(
                        dev, srq, &wqe, &wqe_end, bytes_copied);
        }

        if (ret < 0 || wqe >= wqe_end)
                goto resolve_page_fault;

        ret = pagefault_data_segments(dev, pfault, wqe, wqe_end, &bytes_mapped,
                                      &total_wqe_bytes, !sq);
        if (ret == -EAGAIN)
                goto out;

        if (ret < 0 || total_wqe_bytes > bytes_mapped)
                goto resolve_page_fault;

out:
        ret = 0;
        resume_with_error = 0;

read_user:
        if (ret)
                mlx5_ib_err(
                        dev,
                        "Failed reading a WQE following page fault, error %d, wqe_index %x, qpn %x\n",
                        ret, wqe_index, pfault->token);

resolve_page_fault:
        mlx5_ib_page_fault_resume(dev, pfault, resume_with_error);
        mlx5_ib_dbg(dev, "PAGE FAULT completed. QP 0x%x resume_with_error=%d, type: 0x%x\n",
                    pfault->wqe.wq_num, resume_with_error,
                    pfault->type);
        mlx5_core_res_put(res);
        free_page((unsigned long)wqe_start);
}

static int pages_in_range(u64 address, u32 length)
{
        return (ALIGN(address + length, PAGE_SIZE) -
                (address & PAGE_MASK)) >> PAGE_SHIFT;
}

static void mlx5_ib_mr_rdma_pfault_handler(struct mlx5_ib_dev *dev,
                                           struct mlx5_pagefault *pfault)
{
        u64 address;
        u32 length;
        u32 prefetch_len = pfault->bytes_committed;
        int prefetch_activated = 0;
        u32 rkey = pfault->rdma.r_key;
        int ret;

        /* The RDMA responder handler handles the page fault in two parts.
         * First it brings the necessary pages for the current packet
         * (and uses the pfault context), and then (after resuming the QP)
         * prefetches more pages. The second operation cannot use the pfault
         * context and therefore uses the dummy_pfault context allocated on
         * the stack */
        pfault->rdma.rdma_va += pfault->bytes_committed;
        pfault->rdma.rdma_op_len -= min(pfault->bytes_committed,
                                         pfault->rdma.rdma_op_len);
        pfault->bytes_committed = 0;

        address = pfault->rdma.rdma_va;
        length  = pfault->rdma.rdma_op_len;

        /* For some operations, the hardware cannot tell the exact message
         * length, and in those cases it reports zero. Use prefetch
         * logic. */
        if (length == 0) {
                prefetch_activated = 1;
                length = pfault->rdma.packet_size;
                prefetch_len = min(MAX_PREFETCH_LEN, prefetch_len);
        }

        ret = pagefault_single_data_segment(dev, NULL, rkey, address, length,
                                            &pfault->bytes_committed, NULL);
        if (ret == -EAGAIN) {
                /* We're racing with an invalidation, don't prefetch */
                prefetch_activated = 0;
        } else if (ret < 0 || pages_in_range(address, length) > ret) {
                mlx5_ib_page_fault_resume(dev, pfault, 1);
                if (ret != -ENOENT)
                        mlx5_ib_dbg(dev, "PAGE FAULT error %d. QP 0x%x, type: 0x%x\n",
                                    ret, pfault->token, pfault->type);
                return;
        }

        mlx5_ib_page_fault_resume(dev, pfault, 0);
        mlx5_ib_dbg(dev, "PAGE FAULT completed. QP 0x%x, type: 0x%x, prefetch_activated: %d\n",
                    pfault->token, pfault->type,
                    prefetch_activated);

        /* At this point, there might be a new pagefault already arriving in
         * the eq, switch to the dummy pagefault for the rest of the
         * processing. We're still OK with the objects being alive as the
         * work-queue is being fenced. */

        if (prefetch_activated) {
                u32 bytes_committed = 0;

                ret = pagefault_single_data_segment(dev, NULL, rkey, address,
                                                    prefetch_len,
                                                    &bytes_committed, NULL);
                if (ret < 0 && ret != -EAGAIN) {
                        mlx5_ib_dbg(dev, "Prefetch failed. ret: %d, QP 0x%x, address: 0x%.16llx, length = 0x%.16x\n",
                                    ret, pfault->token, address, prefetch_len);
                }
        }
}

static void mlx5_ib_pfault(struct mlx5_ib_dev *dev, struct mlx5_pagefault *pfault)
{
        u8 event_subtype = pfault->event_subtype;

        switch (event_subtype) {
        case MLX5_PFAULT_SUBTYPE_WQE:
                mlx5_ib_mr_wqe_pfault_handler(dev, pfault);
                break;
        case MLX5_PFAULT_SUBTYPE_RDMA:
                mlx5_ib_mr_rdma_pfault_handler(dev, pfault);
                break;
        default:
                mlx5_ib_err(dev, "Invalid page fault event subtype: 0x%x\n",
                            event_subtype);
                mlx5_ib_page_fault_resume(dev, pfault, 1);
        }
}

static void mlx5_ib_eqe_pf_action(struct work_struct *work)
{
        struct mlx5_pagefault *pfault = container_of(work,
                                                     struct mlx5_pagefault,
                                                     work);
        struct mlx5_ib_pf_eq *eq = pfault->eq;

        mlx5_ib_pfault(eq->dev, pfault);
        mempool_free(pfault, eq->pool);
}

static void mlx5_ib_eq_pf_process(struct mlx5_ib_pf_eq *eq)
{
        struct mlx5_eqe_page_fault *pf_eqe;
        struct mlx5_pagefault *pfault;
        struct mlx5_eqe *eqe;
        int cc = 0;

        while ((eqe = mlx5_eq_get_eqe(eq->core, cc))) {
                pfault = mempool_alloc(eq->pool, GFP_ATOMIC);
                if (!pfault) {
                        schedule_work(&eq->work);
                        break;
                }

                pf_eqe = &eqe->data.page_fault;
                pfault->event_subtype = eqe->sub_type;
                pfault->bytes_committed = be32_to_cpu(pf_eqe->bytes_committed);

                mlx5_ib_dbg(eq->dev,
                            "PAGE_FAULT: subtype: 0x%02x, bytes_committed: 0x%06x\n",
                            eqe->sub_type, pfault->bytes_committed);

                switch (eqe->sub_type) {
                case MLX5_PFAULT_SUBTYPE_RDMA:
                        /* RDMA based event */
                        pfault->type =
                                be32_to_cpu(pf_eqe->rdma.pftype_token) >> 24;
                        pfault->token =
                                be32_to_cpu(pf_eqe->rdma.pftype_token) &
                                MLX5_24BIT_MASK;
                        pfault->rdma.r_key =
                                be32_to_cpu(pf_eqe->rdma.r_key);
                        pfault->rdma.packet_size =
                                be16_to_cpu(pf_eqe->rdma.packet_length);
                        pfault->rdma.rdma_op_len =
                                be32_to_cpu(pf_eqe->rdma.rdma_op_len);
                        pfault->rdma.rdma_va =
                                be64_to_cpu(pf_eqe->rdma.rdma_va);
                        mlx5_ib_dbg(eq->dev,
                                    "PAGE_FAULT: type:0x%x, token: 0x%06x, r_key: 0x%08x\n",
                                    pfault->type, pfault->token,
                                    pfault->rdma.r_key);
                        mlx5_ib_dbg(eq->dev,
                                    "PAGE_FAULT: rdma_op_len: 0x%08x, rdma_va: 0x%016llx\n",
                                    pfault->rdma.rdma_op_len,
                                    pfault->rdma.rdma_va);
                        break;

                case MLX5_PFAULT_SUBTYPE_WQE:
                        /* WQE based event */
                        pfault->type =
                                (be32_to_cpu(pf_eqe->wqe.pftype_wq) >> 24) & 0x7;
                        pfault->token =
                                be32_to_cpu(pf_eqe->wqe.token);
                        pfault->wqe.wq_num =
                                be32_to_cpu(pf_eqe->wqe.pftype_wq) &
                                MLX5_24BIT_MASK;
                        pfault->wqe.wqe_index =
                                be16_to_cpu(pf_eqe->wqe.wqe_index);
                        pfault->wqe.packet_size =
                                be16_to_cpu(pf_eqe->wqe.packet_length);
                        mlx5_ib_dbg(eq->dev,
                                    "PAGE_FAULT: type:0x%x, token: 0x%06x, wq_num: 0x%06x, wqe_index: 0x%04x\n",
                                    pfault->type, pfault->token,
                                    pfault->wqe.wq_num,
                                    pfault->wqe.wqe_index);
                        break;

                default:
                        mlx5_ib_warn(eq->dev,
                                     "Unsupported page fault event sub-type: 0x%02hhx\n",
                                     eqe->sub_type);
                        /* Unsupported page faults should still be
                         * resolved by the page fault handler
                         */
                }

                pfault->eq = eq;
                INIT_WORK(&pfault->work, mlx5_ib_eqe_pf_action);
                queue_work(eq->wq, &pfault->work);

                cc = mlx5_eq_update_cc(eq->core, ++cc);
        }

        mlx5_eq_update_ci(eq->core, cc, 1);
}

static int mlx5_ib_eq_pf_int(struct notifier_block *nb, unsigned long type,
                             void *data)
{
        struct mlx5_ib_pf_eq *eq =
                container_of(nb, struct mlx5_ib_pf_eq, irq_nb);
        unsigned long flags;

        if (spin_trylock_irqsave(&eq->lock, flags)) {
                mlx5_ib_eq_pf_process(eq);
                spin_unlock_irqrestore(&eq->lock, flags);
        } else {
                schedule_work(&eq->work);
        }

        return IRQ_HANDLED;
}

/* mempool_refill() was proposed but unfortunately wasn't accepted
 * http://lkml.iu.edu/hypermail/linux/kernel/1512.1/05073.html
 * Cheap workaround.
 */
static void mempool_refill(mempool_t *pool)
{
        while (pool->curr_nr < pool->min_nr)
                mempool_free(mempool_alloc(pool, GFP_KERNEL), pool);
}

static void mlx5_ib_eq_pf_action(struct work_struct *work)
{
        struct mlx5_ib_pf_eq *eq =
                container_of(work, struct mlx5_ib_pf_eq, work);

        mempool_refill(eq->pool);

        spin_lock_irq(&eq->lock);
        mlx5_ib_eq_pf_process(eq);
        spin_unlock_irq(&eq->lock);
}

enum {
        MLX5_IB_NUM_PF_EQE      = 0x1000,
        MLX5_IB_NUM_PF_DRAIN    = 64,
};

static int
mlx5_ib_create_pf_eq(struct mlx5_ib_dev *dev, struct mlx5_ib_pf_eq *eq)
{
        struct mlx5_eq_param param = {};
        int err;

        INIT_WORK(&eq->work, mlx5_ib_eq_pf_action);
        spin_lock_init(&eq->lock);
        eq->dev = dev;

        eq->pool = mempool_create_kmalloc_pool(MLX5_IB_NUM_PF_DRAIN,
                                               sizeof(struct mlx5_pagefault));
        if (!eq->pool)
                return -ENOMEM;

        eq->wq = alloc_workqueue("mlx5_ib_page_fault",
                                 WQ_HIGHPRI | WQ_UNBOUND | WQ_MEM_RECLAIM,
                                 MLX5_NUM_CMD_EQE);
        if (!eq->wq) {
                err = -ENOMEM;
                goto err_mempool;
        }

        eq->irq_nb.notifier_call = mlx5_ib_eq_pf_int;
        param = (struct mlx5_eq_param) {
                .irq_index = 0,
                .nent = MLX5_IB_NUM_PF_EQE,
        };
        param.mask[0] = 1ull << MLX5_EVENT_TYPE_PAGE_FAULT;
        eq->core = mlx5_eq_create_generic(dev->mdev, &param);
        if (IS_ERR(eq->core)) {
                err = PTR_ERR(eq->core);
                goto err_wq;
        }
        err = mlx5_eq_enable(dev->mdev, eq->core, &eq->irq_nb);
        if (err) {
                mlx5_ib_err(dev, "failed to enable odp EQ %d\n", err);
                goto err_eq;
        }

        return 0;
err_eq:
        mlx5_eq_destroy_generic(dev->mdev, eq->core);
err_wq:
        destroy_workqueue(eq->wq);
err_mempool:
        mempool_destroy(eq->pool);
        return err;
}

static int
mlx5_ib_destroy_pf_eq(struct mlx5_ib_dev *dev, struct mlx5_ib_pf_eq *eq)
{
        int err;

        mlx5_eq_disable(dev->mdev, eq->core, &eq->irq_nb);
        err = mlx5_eq_destroy_generic(dev->mdev, eq->core);
        cancel_work_sync(&eq->work);
        destroy_workqueue(eq->wq);
        mempool_destroy(eq->pool);

        return err;
}

void mlx5_odp_init_mr_cache_entry(struct mlx5_cache_ent *ent)
{
        if (!(ent->dev->odp_caps.general_caps & IB_ODP_SUPPORT_IMPLICIT))
                return;

        switch (ent->order - 2) {
        case MLX5_IMR_MTT_CACHE_ENTRY:
                ent->page = PAGE_SHIFT;
                ent->xlt = MLX5_IMR_MTT_ENTRIES *
                           sizeof(struct mlx5_mtt) /
                           MLX5_IB_UMR_OCTOWORD;
                ent->access_mode = MLX5_MKC_ACCESS_MODE_MTT;
                ent->limit = 0;
                break;

        case MLX5_IMR_KSM_CACHE_ENTRY:
                ent->page = MLX5_KSM_PAGE_SHIFT;
                ent->xlt = mlx5_imr_ksm_entries *
                           sizeof(struct mlx5_klm) /
                           MLX5_IB_UMR_OCTOWORD;
                ent->access_mode = MLX5_MKC_ACCESS_MODE_KSM;
                ent->limit = 0;
                break;
        }
}

static const struct ib_device_ops mlx5_ib_dev_odp_ops = {
        .advise_mr = mlx5_ib_advise_mr,
};

int mlx5_ib_odp_init_one(struct mlx5_ib_dev *dev)
{
        int ret = 0;

        if (!(dev->odp_caps.general_caps & IB_ODP_SUPPORT))
                return ret;

        ib_set_device_ops(&dev->ib_dev, &mlx5_ib_dev_odp_ops);

        if (dev->odp_caps.general_caps & IB_ODP_SUPPORT_IMPLICIT) {
                ret = mlx5_cmd_null_mkey(dev->mdev, &dev->null_mkey);
                if (ret) {
                        mlx5_ib_err(dev, "Error getting null_mkey %d\n", ret);
                        return ret;
                }
        }

        ret = mlx5_ib_create_pf_eq(dev, &dev->odp_pf_eq);

        return ret;
}

void mlx5_ib_odp_cleanup_one(struct mlx5_ib_dev *dev)
{
        if (!(dev->odp_caps.general_caps & IB_ODP_SUPPORT))
                return;

        mlx5_ib_destroy_pf_eq(dev, &dev->odp_pf_eq);
}

int mlx5_ib_odp_init(void)
{
        mlx5_imr_ksm_entries = BIT_ULL(get_order(TASK_SIZE) -
                                       MLX5_IMR_MTT_BITS);

        return 0;
}

struct prefetch_mr_work {
        struct work_struct work;
        u32 pf_flags;
        u32 num_sge;
        struct {
                u64 io_virt;
                struct mlx5_ib_mr *mr;
                size_t length;
        } frags[];
};

static void destroy_prefetch_work(struct prefetch_mr_work *work)
{
        u32 i;

        for (i = 0; i < work->num_sge; ++i)
                if (atomic_dec_and_test(&work->frags[i].mr->num_deferred_work))
                        wake_up(&work->frags[i].mr->q_deferred_work);
        kvfree(work);
}

static struct mlx5_ib_mr *
get_prefetchable_mr(struct ib_pd *pd, enum ib_uverbs_advise_mr_advice advice,
                    u32 lkey)
{
        struct mlx5_ib_dev *dev = to_mdev(pd->device);
        struct mlx5_core_mkey *mmkey;
        struct ib_umem_odp *odp;
        struct mlx5_ib_mr *mr;

        lockdep_assert_held(&dev->odp_srcu);

        mmkey = xa_load(&dev->odp_mkeys, mlx5_base_mkey(lkey));
        if (!mmkey || mmkey->key != lkey || mmkey->type != MLX5_MKEY_MR)
                return NULL;

        mr = container_of(mmkey, struct mlx5_ib_mr, mmkey);

        if (mr->ibmr.pd != pd)
                return NULL;

        odp = to_ib_umem_odp(mr->umem);

        /* prefetch with write-access must be supported by the MR */
        if (advice == IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_WRITE &&
            !odp->umem.writable)
                return NULL;

        return mr;
}

static void mlx5_ib_prefetch_mr_work(struct work_struct *w)
{
        struct prefetch_mr_work *work =
                container_of(w, struct prefetch_mr_work, work);
        struct mlx5_ib_dev *dev;
        u32 bytes_mapped = 0;
        int srcu_key;
        int ret;
        u32 i;

        /* We rely on IB/core that work is executed if we have num_sge != 0 only. */
        WARN_ON(!work->num_sge);
        dev = work->frags[0].mr->dev;
        /* SRCU should be held when calling to mlx5_odp_populate_xlt() */
        srcu_key = srcu_read_lock(&dev->odp_srcu);
        for (i = 0; i < work->num_sge; ++i) {
                ret = pagefault_mr(work->frags[i].mr, work->frags[i].io_virt,
                                   work->frags[i].length, &bytes_mapped,
                                   work->pf_flags);
                if (ret <= 0)
                        continue;
                mlx5_update_odp_stats(work->frags[i].mr, prefetch, ret);
        }
        srcu_read_unlock(&dev->odp_srcu, srcu_key);

        destroy_prefetch_work(work);
}

static bool init_prefetch_work(struct ib_pd *pd,
                               enum ib_uverbs_advise_mr_advice advice,
                               u32 pf_flags, struct prefetch_mr_work *work,
                               struct ib_sge *sg_list, u32 num_sge)
{
        u32 i;

        INIT_WORK(&work->work, mlx5_ib_prefetch_mr_work);
        work->pf_flags = pf_flags;

        for (i = 0; i < num_sge; ++i) {
                work->frags[i].io_virt = sg_list[i].addr;
                work->frags[i].length = sg_list[i].length;
                work->frags[i].mr =
                        get_prefetchable_mr(pd, advice, sg_list[i].lkey);
                if (!work->frags[i].mr) {
                        work->num_sge = i;
                        return false;
                }

                /* Keep the MR pointer will valid outside the SRCU */
                atomic_inc(&work->frags[i].mr->num_deferred_work);
        }
        work->num_sge = num_sge;
        return true;
}

static int mlx5_ib_prefetch_sg_list(struct ib_pd *pd,
                                    enum ib_uverbs_advise_mr_advice advice,
                                    u32 pf_flags, struct ib_sge *sg_list,
                                    u32 num_sge)
{
        struct mlx5_ib_dev *dev = to_mdev(pd->device);
        u32 bytes_mapped = 0;
        int srcu_key;
        int ret = 0;
        u32 i;

        srcu_key = srcu_read_lock(&dev->odp_srcu);
        for (i = 0; i < num_sge; ++i) {
                struct mlx5_ib_mr *mr;

                mr = get_prefetchable_mr(pd, advice, sg_list[i].lkey);
                if (!mr) {
                        ret = -ENOENT;
                        goto out;
                }
                ret = pagefault_mr(mr, sg_list[i].addr, sg_list[i].length,
                                   &bytes_mapped, pf_flags);
                if (ret < 0)
                        goto out;
                mlx5_update_odp_stats(mr, prefetch, ret);
        }
        ret = 0;

out:
        srcu_read_unlock(&dev->odp_srcu, srcu_key);
        return ret;
}

int mlx5_ib_advise_mr_prefetch(struct ib_pd *pd,
                               enum ib_uverbs_advise_mr_advice advice,
                               u32 flags, struct ib_sge *sg_list, u32 num_sge)
{
        struct mlx5_ib_dev *dev = to_mdev(pd->device);
        u32 pf_flags = 0;
        struct prefetch_mr_work *work;
        int srcu_key;

        if (advice == IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH)
                pf_flags |= MLX5_PF_FLAGS_DOWNGRADE;

        if (flags & IB_UVERBS_ADVISE_MR_FLAG_FLUSH)
                return mlx5_ib_prefetch_sg_list(pd, advice, pf_flags, sg_list,
                                                num_sge);

        work = kvzalloc(struct_size(work, frags, num_sge), GFP_KERNEL);
        if (!work)
                return -ENOMEM;

        srcu_key = srcu_read_lock(&dev->odp_srcu);
        if (!init_prefetch_work(pd, advice, pf_flags, work, sg_list, num_sge)) {
                srcu_read_unlock(&dev->odp_srcu, srcu_key);
                destroy_prefetch_work(work);
                return -EINVAL;
        }
        queue_work(system_unbound_wq, &work->work);
        srcu_read_unlock(&dev->odp_srcu, srcu_key);
        return 0;
}