Merge tag 'iwlwifi-next-for-kalle-2016-07-06' of git://git.kernel.org/pub/scm/linux...

[mirror_ubuntu-bionic-kernel.git] / drivers / infiniband / sw / rdmavt / mr.c

/*
 * Copyright(c) 2016 Intel Corporation.
 *
 * This file is provided under a dual BSD/GPLv2 license.  When using or
 * redistributing this file, you may do so under either license.
 *
 * GPL LICENSE SUMMARY
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * BSD LICENSE
 *
 * 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.
 *  - Neither the name of Intel Corporation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <rdma/ib_umem.h>
#include <rdma/rdma_vt.h>
#include "vt.h"
#include "mr.h"

/**
 * rvt_driver_mr_init - Init MR resources per driver
 * @rdi: rvt dev struct
 *
 * Do any intilization needed when a driver registers with rdmavt.
 *
 * Return: 0 on success or errno on failure
 */
int rvt_driver_mr_init(struct rvt_dev_info *rdi)
{
        unsigned int lkey_table_size = rdi->dparms.lkey_table_size;
        unsigned lk_tab_size;
        int i;

        /*
         * The top hfi1_lkey_table_size bits are used to index the
         * table.  The lower 8 bits can be owned by the user (copied from
         * the LKEY).  The remaining bits act as a generation number or tag.
         */
        if (!lkey_table_size)
                return -EINVAL;

        spin_lock_init(&rdi->lkey_table.lock);

        /* ensure generation is at least 4 bits */
        if (lkey_table_size > RVT_MAX_LKEY_TABLE_BITS) {
                rvt_pr_warn(rdi, "lkey bits %u too large, reduced to %u\n",
                            lkey_table_size, RVT_MAX_LKEY_TABLE_BITS);
                rdi->dparms.lkey_table_size = RVT_MAX_LKEY_TABLE_BITS;
                lkey_table_size = rdi->dparms.lkey_table_size;
        }
        rdi->lkey_table.max = 1 << lkey_table_size;
        lk_tab_size = rdi->lkey_table.max * sizeof(*rdi->lkey_table.table);
        rdi->lkey_table.table = (struct rvt_mregion __rcu **)
                               vmalloc_node(lk_tab_size, rdi->dparms.node);
        if (!rdi->lkey_table.table)
                return -ENOMEM;

        RCU_INIT_POINTER(rdi->dma_mr, NULL);
        for (i = 0; i < rdi->lkey_table.max; i++)
                RCU_INIT_POINTER(rdi->lkey_table.table[i], NULL);

        return 0;
}

/**
 *rvt_mr_exit: clean up MR
 *@rdi: rvt dev structure
 *
 * called when drivers have unregistered or perhaps failed to register with us
 */
void rvt_mr_exit(struct rvt_dev_info *rdi)
{
        if (rdi->dma_mr)
                rvt_pr_err(rdi, "DMA MR not null!\n");

        vfree(rdi->lkey_table.table);
}

static void rvt_deinit_mregion(struct rvt_mregion *mr)
{
        int i = mr->mapsz;

        mr->mapsz = 0;
        while (i)
                kfree(mr->map[--i]);
}

static int rvt_init_mregion(struct rvt_mregion *mr, struct ib_pd *pd,
                            int count)
{
        int m, i = 0;
        struct rvt_dev_info *dev = ib_to_rvt(pd->device);

        mr->mapsz = 0;
        m = (count + RVT_SEGSZ - 1) / RVT_SEGSZ;
        for (; i < m; i++) {
                mr->map[i] = kzalloc_node(sizeof(*mr->map[0]), GFP_KERNEL,
                                          dev->dparms.node);
                if (!mr->map[i]) {
                        rvt_deinit_mregion(mr);
                        return -ENOMEM;
                }
                mr->mapsz++;
        }
        init_completion(&mr->comp);
        /* count returning the ptr to user */
        atomic_set(&mr->refcount, 1);
        mr->pd = pd;
        mr->max_segs = count;
        return 0;
}

/**
 * rvt_alloc_lkey - allocate an lkey
 * @mr: memory region that this lkey protects
 * @dma_region: 0->normal key, 1->restricted DMA key
 *
 * Returns 0 if successful, otherwise returns -errno.
 *
 * Increments mr reference count as required.
 *
 * Sets the lkey field mr for non-dma regions.
 *
 */
static int rvt_alloc_lkey(struct rvt_mregion *mr, int dma_region)
{
        unsigned long flags;
        u32 r;
        u32 n;
        int ret = 0;
        struct rvt_dev_info *dev = ib_to_rvt(mr->pd->device);
        struct rvt_lkey_table *rkt = &dev->lkey_table;

        rvt_get_mr(mr);
        spin_lock_irqsave(&rkt->lock, flags);

        /* special case for dma_mr lkey == 0 */
        if (dma_region) {
                struct rvt_mregion *tmr;

                tmr = rcu_access_pointer(dev->dma_mr);
                if (!tmr) {
                        rcu_assign_pointer(dev->dma_mr, mr);
                        mr->lkey_published = 1;
                } else {
                        rvt_put_mr(mr);
                }
                goto success;
        }

        /* Find the next available LKEY */
        r = rkt->next;
        n = r;
        for (;;) {
                if (!rcu_access_pointer(rkt->table[r]))
                        break;
                r = (r + 1) & (rkt->max - 1);
                if (r == n)
                        goto bail;
        }
        rkt->next = (r + 1) & (rkt->max - 1);
        /*
         * Make sure lkey is never zero which is reserved to indicate an
         * unrestricted LKEY.
         */
        rkt->gen++;
        /*
         * bits are capped to ensure enough bits for generation number
         */
        mr->lkey = (r << (32 - dev->dparms.lkey_table_size)) |
                ((((1 << (24 - dev->dparms.lkey_table_size)) - 1) & rkt->gen)
                 << 8);
        if (mr->lkey == 0) {
                mr->lkey |= 1 << 8;
                rkt->gen++;
        }
        rcu_assign_pointer(rkt->table[r], mr);
        mr->lkey_published = 1;
success:
        spin_unlock_irqrestore(&rkt->lock, flags);
out:
        return ret;
bail:
        rvt_put_mr(mr);
        spin_unlock_irqrestore(&rkt->lock, flags);
        ret = -ENOMEM;
        goto out;
}

/**
 * rvt_free_lkey - free an lkey
 * @mr: mr to free from tables
 */
static void rvt_free_lkey(struct rvt_mregion *mr)
{
        unsigned long flags;
        u32 lkey = mr->lkey;
        u32 r;
        struct rvt_dev_info *dev = ib_to_rvt(mr->pd->device);
        struct rvt_lkey_table *rkt = &dev->lkey_table;
        int freed = 0;

        spin_lock_irqsave(&rkt->lock, flags);
        if (!mr->lkey_published)
                goto out;
        if (lkey == 0) {
                RCU_INIT_POINTER(dev->dma_mr, NULL);
        } else {
                r = lkey >> (32 - dev->dparms.lkey_table_size);
                RCU_INIT_POINTER(rkt->table[r], NULL);
        }
        mr->lkey_published = 0;
        freed++;
out:
        spin_unlock_irqrestore(&rkt->lock, flags);
        if (freed) {
                synchronize_rcu();
                rvt_put_mr(mr);
        }
}

static struct rvt_mr *__rvt_alloc_mr(int count, struct ib_pd *pd)
{
        struct rvt_mr *mr;
        int rval = -ENOMEM;
        int m;

        /* Allocate struct plus pointers to first level page tables. */
        m = (count + RVT_SEGSZ - 1) / RVT_SEGSZ;
        mr = kzalloc(sizeof(*mr) + m * sizeof(mr->mr.map[0]), GFP_KERNEL);
        if (!mr)
                goto bail;

        rval = rvt_init_mregion(&mr->mr, pd, count);
        if (rval)
                goto bail;
        /*
         * ib_reg_phys_mr() will initialize mr->ibmr except for
         * lkey and rkey.
         */
        rval = rvt_alloc_lkey(&mr->mr, 0);
        if (rval)
                goto bail_mregion;
        mr->ibmr.lkey = mr->mr.lkey;
        mr->ibmr.rkey = mr->mr.lkey;
done:
        return mr;

bail_mregion:
        rvt_deinit_mregion(&mr->mr);
bail:
        kfree(mr);
        mr = ERR_PTR(rval);
        goto done;
}

static void __rvt_free_mr(struct rvt_mr *mr)
{
        rvt_deinit_mregion(&mr->mr);
        rvt_free_lkey(&mr->mr);
        vfree(mr);
}

/**
 * rvt_get_dma_mr - get a DMA memory region
 * @pd: protection domain for this memory region
 * @acc: access flags
 *
 * Return: the memory region on success, otherwise returns an errno.
 * Note that all DMA addresses should be created via the
 * struct ib_dma_mapping_ops functions (see dma.c).
 */
struct ib_mr *rvt_get_dma_mr(struct ib_pd *pd, int acc)
{
        struct rvt_mr *mr;
        struct ib_mr *ret;
        int rval;

        if (ibpd_to_rvtpd(pd)->user)
                return ERR_PTR(-EPERM);

        mr = kzalloc(sizeof(*mr), GFP_KERNEL);
        if (!mr) {
                ret = ERR_PTR(-ENOMEM);
                goto bail;
        }

        rval = rvt_init_mregion(&mr->mr, pd, 0);
        if (rval) {
                ret = ERR_PTR(rval);
                goto bail;
        }

        rval = rvt_alloc_lkey(&mr->mr, 1);
        if (rval) {
                ret = ERR_PTR(rval);
                goto bail_mregion;
        }

        mr->mr.access_flags = acc;
        ret = &mr->ibmr;
done:
        return ret;

bail_mregion:
        rvt_deinit_mregion(&mr->mr);
bail:
        kfree(mr);
        goto done;
}

/**
 * rvt_reg_user_mr - register a userspace memory region
 * @pd: protection domain for this memory region
 * @start: starting userspace address
 * @length: length of region to register
 * @mr_access_flags: access flags for this memory region
 * @udata: unused by the driver
 *
 * Return: the memory region on success, otherwise returns an errno.
 */
struct ib_mr *rvt_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
                              u64 virt_addr, int mr_access_flags,
                              struct ib_udata *udata)
{
        struct rvt_mr *mr;
        struct ib_umem *umem;
        struct scatterlist *sg;
        int n, m, entry;
        struct ib_mr *ret;

        if (length == 0)
                return ERR_PTR(-EINVAL);

        umem = ib_umem_get(pd->uobject->context, start, length,
                           mr_access_flags, 0);
        if (IS_ERR(umem))
                return (void *)umem;

        n = umem->nmap;

        mr = __rvt_alloc_mr(n, pd);
        if (IS_ERR(mr)) {
                ret = (struct ib_mr *)mr;
                goto bail_umem;
        }

        mr->mr.user_base = start;
        mr->mr.iova = virt_addr;
        mr->mr.length = length;
        mr->mr.offset = ib_umem_offset(umem);
        mr->mr.access_flags = mr_access_flags;
        mr->umem = umem;

        if (is_power_of_2(umem->page_size))
                mr->mr.page_shift = ilog2(umem->page_size);
        m = 0;
        n = 0;
        for_each_sg(umem->sg_head.sgl, sg, umem->nmap, entry) {
                void *vaddr;

                vaddr = page_address(sg_page(sg));
                if (!vaddr) {
                        ret = ERR_PTR(-EINVAL);
                        goto bail_inval;
                }
                mr->mr.map[m]->segs[n].vaddr = vaddr;
                mr->mr.map[m]->segs[n].length = umem->page_size;
                n++;
                if (n == RVT_SEGSZ) {
                        m++;
                        n = 0;
                }
        }
        return &mr->ibmr;

bail_inval:
        __rvt_free_mr(mr);

bail_umem:
        ib_umem_release(umem);

        return ret;
}

/**
 * rvt_dereg_mr - unregister and free a memory region
 * @ibmr: the memory region to free
 *
 *
 * Note that this is called to free MRs created by rvt_get_dma_mr()
 * or rvt_reg_user_mr().
 *
 * Returns 0 on success.
 */
int rvt_dereg_mr(struct ib_mr *ibmr)
{
        struct rvt_mr *mr = to_imr(ibmr);
        struct rvt_dev_info *rdi = ib_to_rvt(ibmr->pd->device);
        int ret = 0;
        unsigned long timeout;

        rvt_free_lkey(&mr->mr);

        rvt_put_mr(&mr->mr); /* will set completion if last */
        timeout = wait_for_completion_timeout(&mr->mr.comp, 5 * HZ);
        if (!timeout) {
                rvt_pr_err(rdi,
                           "rvt_dereg_mr timeout mr %p pd %p refcount %u\n",
                           mr, mr->mr.pd, atomic_read(&mr->mr.refcount));
                rvt_get_mr(&mr->mr);
                ret = -EBUSY;
                goto out;
        }
        rvt_deinit_mregion(&mr->mr);
        if (mr->umem)
                ib_umem_release(mr->umem);
        kfree(mr);
out:
        return ret;
}

/**
 * rvt_alloc_mr - Allocate a memory region usable with the
 * @pd: protection domain for this memory region
 * @mr_type: mem region type
 * @max_num_sg: Max number of segments allowed
 *
 * Return: the memory region on success, otherwise return an errno.
 */
struct ib_mr *rvt_alloc_mr(struct ib_pd *pd,
                           enum ib_mr_type mr_type,
                           u32 max_num_sg)
{
        struct rvt_mr *mr;

        if (mr_type != IB_MR_TYPE_MEM_REG)
                return ERR_PTR(-EINVAL);

        mr = __rvt_alloc_mr(max_num_sg, pd);
        if (IS_ERR(mr))
                return (struct ib_mr *)mr;

        return &mr->ibmr;
}

/**
 * rvt_alloc_fmr - allocate a fast memory region
 * @pd: the protection domain for this memory region
 * @mr_access_flags: access flags for this memory region
 * @fmr_attr: fast memory region attributes
 *
 * Return: the memory region on success, otherwise returns an errno.
 */
struct ib_fmr *rvt_alloc_fmr(struct ib_pd *pd, int mr_access_flags,
                             struct ib_fmr_attr *fmr_attr)
{
        struct rvt_fmr *fmr;
        int m;
        struct ib_fmr *ret;
        int rval = -ENOMEM;

        /* Allocate struct plus pointers to first level page tables. */
        m = (fmr_attr->max_pages + RVT_SEGSZ - 1) / RVT_SEGSZ;
        fmr = kzalloc(sizeof(*fmr) + m * sizeof(fmr->mr.map[0]), GFP_KERNEL);
        if (!fmr)
                goto bail;

        rval = rvt_init_mregion(&fmr->mr, pd, fmr_attr->max_pages);
        if (rval)
                goto bail;

        /*
         * ib_alloc_fmr() will initialize fmr->ibfmr except for lkey &
         * rkey.
         */
        rval = rvt_alloc_lkey(&fmr->mr, 0);
        if (rval)
                goto bail_mregion;
        fmr->ibfmr.rkey = fmr->mr.lkey;
        fmr->ibfmr.lkey = fmr->mr.lkey;
        /*
         * Resources are allocated but no valid mapping (RKEY can't be
         * used).
         */
        fmr->mr.access_flags = mr_access_flags;
        fmr->mr.max_segs = fmr_attr->max_pages;
        fmr->mr.page_shift = fmr_attr->page_shift;

        ret = &fmr->ibfmr;
done:
        return ret;

bail_mregion:
        rvt_deinit_mregion(&fmr->mr);
bail:
        kfree(fmr);
        ret = ERR_PTR(rval);
        goto done;
}

/**
 * rvt_map_phys_fmr - set up a fast memory region
 * @ibmfr: the fast memory region to set up
 * @page_list: the list of pages to associate with the fast memory region
 * @list_len: the number of pages to associate with the fast memory region
 * @iova: the virtual address of the start of the fast memory region
 *
 * This may be called from interrupt context.
 *
 * Return: 0 on success
 */

int rvt_map_phys_fmr(struct ib_fmr *ibfmr, u64 *page_list,
                     int list_len, u64 iova)
{
        struct rvt_fmr *fmr = to_ifmr(ibfmr);
        struct rvt_lkey_table *rkt;
        unsigned long flags;
        int m, n, i;
        u32 ps;
        struct rvt_dev_info *rdi = ib_to_rvt(ibfmr->device);

        i = atomic_read(&fmr->mr.refcount);
        if (i > 2)
                return -EBUSY;

        if (list_len > fmr->mr.max_segs)
                return -EINVAL;

        rkt = &rdi->lkey_table;
        spin_lock_irqsave(&rkt->lock, flags);
        fmr->mr.user_base = iova;
        fmr->mr.iova = iova;
        ps = 1 << fmr->mr.page_shift;
        fmr->mr.length = list_len * ps;
        m = 0;
        n = 0;
        for (i = 0; i < list_len; i++) {
                fmr->mr.map[m]->segs[n].vaddr = (void *)page_list[i];
                fmr->mr.map[m]->segs[n].length = ps;
                if (++n == RVT_SEGSZ) {
                        m++;
                        n = 0;
                }
        }
        spin_unlock_irqrestore(&rkt->lock, flags);
        return 0;
}

/**
 * rvt_unmap_fmr - unmap fast memory regions
 * @fmr_list: the list of fast memory regions to unmap
 *
 * Return: 0 on success.
 */
int rvt_unmap_fmr(struct list_head *fmr_list)
{
        struct rvt_fmr *fmr;
        struct rvt_lkey_table *rkt;
        unsigned long flags;
        struct rvt_dev_info *rdi;

        list_for_each_entry(fmr, fmr_list, ibfmr.list) {
                rdi = ib_to_rvt(fmr->ibfmr.device);
                rkt = &rdi->lkey_table;
                spin_lock_irqsave(&rkt->lock, flags);
                fmr->mr.user_base = 0;
                fmr->mr.iova = 0;
                fmr->mr.length = 0;
                spin_unlock_irqrestore(&rkt->lock, flags);
        }
        return 0;
}

/**
 * rvt_dealloc_fmr - deallocate a fast memory region
 * @ibfmr: the fast memory region to deallocate
 *
 * Return: 0 on success.
 */
int rvt_dealloc_fmr(struct ib_fmr *ibfmr)
{
        struct rvt_fmr *fmr = to_ifmr(ibfmr);
        int ret = 0;
        unsigned long timeout;

        rvt_free_lkey(&fmr->mr);
        rvt_put_mr(&fmr->mr); /* will set completion if last */
        timeout = wait_for_completion_timeout(&fmr->mr.comp, 5 * HZ);
        if (!timeout) {
                rvt_get_mr(&fmr->mr);
                ret = -EBUSY;
                goto out;
        }
        rvt_deinit_mregion(&fmr->mr);
        kfree(fmr);
out:
        return ret;
}

/**
 * rvt_lkey_ok - check IB SGE for validity and initialize
 * @rkt: table containing lkey to check SGE against
 * @pd: protection domain
 * @isge: outgoing internal SGE
 * @sge: SGE to check
 * @acc: access flags
 *
 * Check the IB SGE for validity and initialize our internal version
 * of it.
 *
 * Return: 1 if valid and successful, otherwise returns 0.
 *
 * increments the reference count upon success
 *
 */
int rvt_lkey_ok(struct rvt_lkey_table *rkt, struct rvt_pd *pd,
                struct rvt_sge *isge, struct ib_sge *sge, int acc)
{
        struct rvt_mregion *mr;
        unsigned n, m;
        size_t off;
        struct rvt_dev_info *dev = ib_to_rvt(pd->ibpd.device);

        /*
         * We use LKEY == zero for kernel virtual addresses
         * (see rvt_get_dma_mr and dma.c).
         */
        rcu_read_lock();
        if (sge->lkey == 0) {
                if (pd->user)
                        goto bail;
                mr = rcu_dereference(dev->dma_mr);
                if (!mr)
                        goto bail;
                atomic_inc(&mr->refcount);
                rcu_read_unlock();

                isge->mr = mr;
                isge->vaddr = (void *)sge->addr;
                isge->length = sge->length;
                isge->sge_length = sge->length;
                isge->m = 0;
                isge->n = 0;
                goto ok;
        }
        mr = rcu_dereference(
                rkt->table[(sge->lkey >> (32 - dev->dparms.lkey_table_size))]);
        if (unlikely(!mr || mr->lkey != sge->lkey || mr->pd != &pd->ibpd))
                goto bail;

        off = sge->addr - mr->user_base;
        if (unlikely(sge->addr < mr->user_base ||
                     off + sge->length > mr->length ||
                     (mr->access_flags & acc) != acc))
                goto bail;
        atomic_inc(&mr->refcount);
        rcu_read_unlock();

        off += mr->offset;
        if (mr->page_shift) {
                /*
                 * page sizes are uniform power of 2 so no loop is necessary
                 * entries_spanned_by_off is the number of times the loop below
                 * would have executed.
                */
                size_t entries_spanned_by_off;

                entries_spanned_by_off = off >> mr->page_shift;
                off -= (entries_spanned_by_off << mr->page_shift);
                m = entries_spanned_by_off / RVT_SEGSZ;
                n = entries_spanned_by_off % RVT_SEGSZ;
        } else {
                m = 0;
                n = 0;
                while (off >= mr->map[m]->segs[n].length) {
                        off -= mr->map[m]->segs[n].length;
                        n++;
                        if (n >= RVT_SEGSZ) {
                                m++;
                                n = 0;
                        }
                }
        }
        isge->mr = mr;
        isge->vaddr = mr->map[m]->segs[n].vaddr + off;
        isge->length = mr->map[m]->segs[n].length - off;
        isge->sge_length = sge->length;
        isge->m = m;
        isge->n = n;
ok:
        return 1;
bail:
        rcu_read_unlock();
        return 0;
}
EXPORT_SYMBOL(rvt_lkey_ok);

/**
 * rvt_rkey_ok - check the IB virtual address, length, and RKEY
 * @qp: qp for validation
 * @sge: SGE state
 * @len: length of data
 * @vaddr: virtual address to place data
 * @rkey: rkey to check
 * @acc: access flags
 *
 * Return: 1 if successful, otherwise 0.
 *
 * increments the reference count upon success
 */
int rvt_rkey_ok(struct rvt_qp *qp, struct rvt_sge *sge,
                u32 len, u64 vaddr, u32 rkey, int acc)
{
        struct rvt_dev_info *dev = ib_to_rvt(qp->ibqp.device);
        struct rvt_lkey_table *rkt = &dev->lkey_table;
        struct rvt_mregion *mr;
        unsigned n, m;
        size_t off;

        /*
         * We use RKEY == zero for kernel virtual addresses
         * (see rvt_get_dma_mr and dma.c).
         */
        rcu_read_lock();
        if (rkey == 0) {
                struct rvt_pd *pd = ibpd_to_rvtpd(qp->ibqp.pd);
                struct rvt_dev_info *rdi = ib_to_rvt(pd->ibpd.device);

                if (pd->user)
                        goto bail;
                mr = rcu_dereference(rdi->dma_mr);
                if (!mr)
                        goto bail;
                atomic_inc(&mr->refcount);
                rcu_read_unlock();

                sge->mr = mr;
                sge->vaddr = (void *)vaddr;
                sge->length = len;
                sge->sge_length = len;
                sge->m = 0;
                sge->n = 0;
                goto ok;
        }

        mr = rcu_dereference(
                rkt->table[(rkey >> (32 - dev->dparms.lkey_table_size))]);
        if (unlikely(!mr || mr->lkey != rkey || qp->ibqp.pd != mr->pd))
                goto bail;

        off = vaddr - mr->iova;
        if (unlikely(vaddr < mr->iova || off + len > mr->length ||
                     (mr->access_flags & acc) == 0))
                goto bail;
        atomic_inc(&mr->refcount);
        rcu_read_unlock();

        off += mr->offset;
        if (mr->page_shift) {
                /*
                 * page sizes are uniform power of 2 so no loop is necessary
                 * entries_spanned_by_off is the number of times the loop below
                 * would have executed.
                */
                size_t entries_spanned_by_off;

                entries_spanned_by_off = off >> mr->page_shift;
                off -= (entries_spanned_by_off << mr->page_shift);
                m = entries_spanned_by_off / RVT_SEGSZ;
                n = entries_spanned_by_off % RVT_SEGSZ;
        } else {
                m = 0;
                n = 0;
                while (off >= mr->map[m]->segs[n].length) {
                        off -= mr->map[m]->segs[n].length;
                        n++;
                        if (n >= RVT_SEGSZ) {
                                m++;
                                n = 0;
                        }
                }
        }
        sge->mr = mr;
        sge->vaddr = mr->map[m]->segs[n].vaddr + off;
        sge->length = mr->map[m]->segs[n].length - off;
        sge->sge_length = len;
        sge->m = m;
        sge->n = n;
ok:
        return 1;
bail:
        rcu_read_unlock();
        return 0;
}
EXPORT_SYMBOL(rvt_rkey_ok);