Merge tag 'block-5.11-2021-01-10' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / drivers / infiniband / hw / hfi1 / user_exp_rcv.c

/*
 * Copyright(c) 2020 Cornelis Networks, Inc.
 * Copyright(c) 2015-2018 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 <asm/page.h>
#include <linux/string.h>

#include "mmu_rb.h"
#include "user_exp_rcv.h"
#include "trace.h"

static void unlock_exp_tids(struct hfi1_ctxtdata *uctxt,
                            struct exp_tid_set *set,
                            struct hfi1_filedata *fd);
static u32 find_phys_blocks(struct tid_user_buf *tidbuf, unsigned int npages);
static int set_rcvarray_entry(struct hfi1_filedata *fd,
                              struct tid_user_buf *tbuf,
                              u32 rcventry, struct tid_group *grp,
                              u16 pageidx, unsigned int npages);
static void cacheless_tid_rb_remove(struct hfi1_filedata *fdata,
                                    struct tid_rb_node *tnode);
static bool tid_rb_invalidate(struct mmu_interval_notifier *mni,
                              const struct mmu_notifier_range *range,
                              unsigned long cur_seq);
static int program_rcvarray(struct hfi1_filedata *fd, struct tid_user_buf *,
                            struct tid_group *grp,
                            unsigned int start, u16 count,
                            u32 *tidlist, unsigned int *tididx,
                            unsigned int *pmapped);
static int unprogram_rcvarray(struct hfi1_filedata *fd, u32 tidinfo,
                              struct tid_group **grp);
static void clear_tid_node(struct hfi1_filedata *fd, struct tid_rb_node *node);

static const struct mmu_interval_notifier_ops tid_mn_ops = {
        .invalidate = tid_rb_invalidate,
};

/*
 * Initialize context and file private data needed for Expected
 * receive caching. This needs to be done after the context has
 * been configured with the eager/expected RcvEntry counts.
 */
int hfi1_user_exp_rcv_init(struct hfi1_filedata *fd,
                           struct hfi1_ctxtdata *uctxt)
{
        int ret = 0;

        fd->entry_to_rb = kcalloc(uctxt->expected_count,
                                  sizeof(struct rb_node *),
                                  GFP_KERNEL);
        if (!fd->entry_to_rb)
                return -ENOMEM;

        if (!HFI1_CAP_UGET_MASK(uctxt->flags, TID_UNMAP)) {
                fd->invalid_tid_idx = 0;
                fd->invalid_tids = kcalloc(uctxt->expected_count,
                                           sizeof(*fd->invalid_tids),
                                           GFP_KERNEL);
                if (!fd->invalid_tids) {
                        kfree(fd->entry_to_rb);
                        fd->entry_to_rb = NULL;
                        return -ENOMEM;
                }
                fd->use_mn = true;
        }

        /*
         * PSM does not have a good way to separate, count, and
         * effectively enforce a limit on RcvArray entries used by
         * subctxts (when context sharing is used) when TID caching
         * is enabled. To help with that, we calculate a per-process
         * RcvArray entry share and enforce that.
         * If TID caching is not in use, PSM deals with usage on its
         * own. In that case, we allow any subctxt to take all of the
         * entries.
         *
         * Make sure that we set the tid counts only after successful
         * init.
         */
        spin_lock(&fd->tid_lock);
        if (uctxt->subctxt_cnt && fd->use_mn) {
                u16 remainder;

                fd->tid_limit = uctxt->expected_count / uctxt->subctxt_cnt;
                remainder = uctxt->expected_count % uctxt->subctxt_cnt;
                if (remainder && fd->subctxt < remainder)
                        fd->tid_limit++;
        } else {
                fd->tid_limit = uctxt->expected_count;
        }
        spin_unlock(&fd->tid_lock);

        return ret;
}

void hfi1_user_exp_rcv_free(struct hfi1_filedata *fd)
{
        struct hfi1_ctxtdata *uctxt = fd->uctxt;

        mutex_lock(&uctxt->exp_mutex);
        if (!EXP_TID_SET_EMPTY(uctxt->tid_full_list))
                unlock_exp_tids(uctxt, &uctxt->tid_full_list, fd);
        if (!EXP_TID_SET_EMPTY(uctxt->tid_used_list))
                unlock_exp_tids(uctxt, &uctxt->tid_used_list, fd);
        mutex_unlock(&uctxt->exp_mutex);

        kfree(fd->invalid_tids);
        fd->invalid_tids = NULL;

        kfree(fd->entry_to_rb);
        fd->entry_to_rb = NULL;
}

/**
 * Release pinned receive buffer pages.
 *
 * @mapped - true if the pages have been DMA mapped. false otherwise.
 * @idx - Index of the first page to unpin.
 * @npages - No of pages to unpin.
 *
 * If the pages have been DMA mapped (indicated by mapped parameter), their
 * info will be passed via a struct tid_rb_node. If they haven't been mapped,
 * their info will be passed via a struct tid_user_buf.
 */
static void unpin_rcv_pages(struct hfi1_filedata *fd,
                            struct tid_user_buf *tidbuf,
                            struct tid_rb_node *node,
                            unsigned int idx,
                            unsigned int npages,
                            bool mapped)
{
        struct page **pages;
        struct hfi1_devdata *dd = fd->uctxt->dd;
        struct mm_struct *mm;

        if (mapped) {
                pci_unmap_single(dd->pcidev, node->dma_addr,
                                 node->npages * PAGE_SIZE, PCI_DMA_FROMDEVICE);
                pages = &node->pages[idx];
                mm = mm_from_tid_node(node);
        } else {
                pages = &tidbuf->pages[idx];
                mm = current->mm;
        }
        hfi1_release_user_pages(mm, pages, npages, mapped);
        fd->tid_n_pinned -= npages;
}

/**
 * Pin receive buffer pages.
 */
static int pin_rcv_pages(struct hfi1_filedata *fd, struct tid_user_buf *tidbuf)
{
        int pinned;
        unsigned int npages;
        unsigned long vaddr = tidbuf->vaddr;
        struct page **pages = NULL;
        struct hfi1_devdata *dd = fd->uctxt->dd;

        /* Get the number of pages the user buffer spans */
        npages = num_user_pages(vaddr, tidbuf->length);
        if (!npages)
                return -EINVAL;

        if (npages > fd->uctxt->expected_count) {
                dd_dev_err(dd, "Expected buffer too big\n");
                return -EINVAL;
        }

        /* Allocate the array of struct page pointers needed for pinning */
        pages = kcalloc(npages, sizeof(*pages), GFP_KERNEL);
        if (!pages)
                return -ENOMEM;

        /*
         * Pin all the pages of the user buffer. If we can't pin all the
         * pages, accept the amount pinned so far and program only that.
         * User space knows how to deal with partially programmed buffers.
         */
        if (!hfi1_can_pin_pages(dd, current->mm, fd->tid_n_pinned, npages)) {
                kfree(pages);
                return -ENOMEM;
        }

        pinned = hfi1_acquire_user_pages(current->mm, vaddr, npages, true, pages);
        if (pinned <= 0) {
                kfree(pages);
                return pinned;
        }
        tidbuf->pages = pages;
        tidbuf->npages = npages;
        fd->tid_n_pinned += pinned;
        return pinned;
}

/*
 * RcvArray entry allocation for Expected Receives is done by the
 * following algorithm:
 *
 * The context keeps 3 lists of groups of RcvArray entries:
 *   1. List of empty groups - tid_group_list
 *      This list is created during user context creation and
 *      contains elements which describe sets (of 8) of empty
 *      RcvArray entries.
 *   2. List of partially used groups - tid_used_list
 *      This list contains sets of RcvArray entries which are
 *      not completely used up. Another mapping request could
 *      use some of all of the remaining entries.
 *   3. List of full groups - tid_full_list
 *      This is the list where sets that are completely used
 *      up go.
 *
 * An attempt to optimize the usage of RcvArray entries is
 * made by finding all sets of physically contiguous pages in a
 * user's buffer.
 * These physically contiguous sets are further split into
 * sizes supported by the receive engine of the HFI. The
 * resulting sets of pages are stored in struct tid_pageset,
 * which describes the sets as:
 *    * .count - number of pages in this set
 *    * .idx - starting index into struct page ** array
 *                    of this set
 *
 * From this point on, the algorithm deals with the page sets
 * described above. The number of pagesets is divided by the
 * RcvArray group size to produce the number of full groups
 * needed.
 *
 * Groups from the 3 lists are manipulated using the following
 * rules:
 *   1. For each set of 8 pagesets, a complete group from
 *      tid_group_list is taken, programmed, and moved to
 *      the tid_full_list list.
 *   2. For all remaining pagesets:
 *      2.1 If the tid_used_list is empty and the tid_group_list
 *          is empty, stop processing pageset and return only
 *          what has been programmed up to this point.
 *      2.2 If the tid_used_list is empty and the tid_group_list
 *          is not empty, move a group from tid_group_list to
 *          tid_used_list.
 *      2.3 For each group is tid_used_group, program as much as
 *          can fit into the group. If the group becomes fully
 *          used, move it to tid_full_list.
 */
int hfi1_user_exp_rcv_setup(struct hfi1_filedata *fd,
                            struct hfi1_tid_info *tinfo)
{
        int ret = 0, need_group = 0, pinned;
        struct hfi1_ctxtdata *uctxt = fd->uctxt;
        struct hfi1_devdata *dd = uctxt->dd;
        unsigned int ngroups, pageidx = 0, pageset_count,
                tididx = 0, mapped, mapped_pages = 0;
        u32 *tidlist = NULL;
        struct tid_user_buf *tidbuf;

        if (!PAGE_ALIGNED(tinfo->vaddr))
                return -EINVAL;

        tidbuf = kzalloc(sizeof(*tidbuf), GFP_KERNEL);
        if (!tidbuf)
                return -ENOMEM;

        tidbuf->vaddr = tinfo->vaddr;
        tidbuf->length = tinfo->length;
        tidbuf->psets = kcalloc(uctxt->expected_count, sizeof(*tidbuf->psets),
                                GFP_KERNEL);
        if (!tidbuf->psets) {
                kfree(tidbuf);
                return -ENOMEM;
        }

        pinned = pin_rcv_pages(fd, tidbuf);
        if (pinned <= 0) {
                kfree(tidbuf->psets);
                kfree(tidbuf);
                return pinned;
        }

        /* Find sets of physically contiguous pages */
        tidbuf->n_psets = find_phys_blocks(tidbuf, pinned);

        /*
         * We don't need to access this under a lock since tid_used is per
         * process and the same process cannot be in hfi1_user_exp_rcv_clear()
         * and hfi1_user_exp_rcv_setup() at the same time.
         */
        spin_lock(&fd->tid_lock);
        if (fd->tid_used + tidbuf->n_psets > fd->tid_limit)
                pageset_count = fd->tid_limit - fd->tid_used;
        else
                pageset_count = tidbuf->n_psets;
        spin_unlock(&fd->tid_lock);

        if (!pageset_count)
                goto bail;

        ngroups = pageset_count / dd->rcv_entries.group_size;
        tidlist = kcalloc(pageset_count, sizeof(*tidlist), GFP_KERNEL);
        if (!tidlist) {
                ret = -ENOMEM;
                goto nomem;
        }

        tididx = 0;

        /*
         * From this point on, we are going to be using shared (between master
         * and subcontexts) context resources. We need to take the lock.
         */
        mutex_lock(&uctxt->exp_mutex);
        /*
         * The first step is to program the RcvArray entries which are complete
         * groups.
         */
        while (ngroups && uctxt->tid_group_list.count) {
                struct tid_group *grp =
                        tid_group_pop(&uctxt->tid_group_list);

                ret = program_rcvarray(fd, tidbuf, grp,
                                       pageidx, dd->rcv_entries.group_size,
                                       tidlist, &tididx, &mapped);
                /*
                 * If there was a failure to program the RcvArray
                 * entries for the entire group, reset the grp fields
                 * and add the grp back to the free group list.
                 */
                if (ret <= 0) {
                        tid_group_add_tail(grp, &uctxt->tid_group_list);
                        hfi1_cdbg(TID,
                                  "Failed to program RcvArray group %d", ret);
                        goto unlock;
                }

                tid_group_add_tail(grp, &uctxt->tid_full_list);
                ngroups--;
                pageidx += ret;
                mapped_pages += mapped;
        }

        while (pageidx < pageset_count) {
                struct tid_group *grp, *ptr;
                /*
                 * If we don't have any partially used tid groups, check
                 * if we have empty groups. If so, take one from there and
                 * put in the partially used list.
                 */
                if (!uctxt->tid_used_list.count || need_group) {
                        if (!uctxt->tid_group_list.count)
                                goto unlock;

                        grp = tid_group_pop(&uctxt->tid_group_list);
                        tid_group_add_tail(grp, &uctxt->tid_used_list);
                        need_group = 0;
                }
                /*
                 * There is an optimization opportunity here - instead of
                 * fitting as many page sets as we can, check for a group
                 * later on in the list that could fit all of them.
                 */
                list_for_each_entry_safe(grp, ptr, &uctxt->tid_used_list.list,
                                         list) {
                        unsigned use = min_t(unsigned, pageset_count - pageidx,
                                             grp->size - grp->used);

                        ret = program_rcvarray(fd, tidbuf, grp,
                                               pageidx, use, tidlist,
                                               &tididx, &mapped);
                        if (ret < 0) {
                                hfi1_cdbg(TID,
                                          "Failed to program RcvArray entries %d",
                                          ret);
                                goto unlock;
                        } else if (ret > 0) {
                                if (grp->used == grp->size)
                                        tid_group_move(grp,
                                                       &uctxt->tid_used_list,
                                                       &uctxt->tid_full_list);
                                pageidx += ret;
                                mapped_pages += mapped;
                                need_group = 0;
                                /* Check if we are done so we break out early */
                                if (pageidx >= pageset_count)
                                        break;
                        } else if (WARN_ON(ret == 0)) {
                                /*
                                 * If ret is 0, we did not program any entries
                                 * into this group, which can only happen if
                                 * we've screwed up the accounting somewhere.
                                 * Warn and try to continue.
                                 */
                                need_group = 1;
                        }
                }
        }
unlock:
        mutex_unlock(&uctxt->exp_mutex);
nomem:
        hfi1_cdbg(TID, "total mapped: tidpairs:%u pages:%u (%d)", tididx,
                  mapped_pages, ret);
        if (tididx) {
                spin_lock(&fd->tid_lock);
                fd->tid_used += tididx;
                spin_unlock(&fd->tid_lock);
                tinfo->tidcnt = tididx;
                tinfo->length = mapped_pages * PAGE_SIZE;

                if (copy_to_user(u64_to_user_ptr(tinfo->tidlist),
                                 tidlist, sizeof(tidlist[0]) * tididx)) {
                        /*
                         * On failure to copy to the user level, we need to undo
                         * everything done so far so we don't leak resources.
                         */
                        tinfo->tidlist = (unsigned long)&tidlist;
                        hfi1_user_exp_rcv_clear(fd, tinfo);
                        tinfo->tidlist = 0;
                        ret = -EFAULT;
                        goto bail;
                }
        }

        /*
         * If not everything was mapped (due to insufficient RcvArray entries,
         * for example), unpin all unmapped pages so we can pin them nex time.
         */
        if (mapped_pages != pinned)
                unpin_rcv_pages(fd, tidbuf, NULL, mapped_pages,
                                (pinned - mapped_pages), false);
bail:
        kfree(tidbuf->psets);
        kfree(tidlist);
        kfree(tidbuf->pages);
        kfree(tidbuf);
        return ret > 0 ? 0 : ret;
}

int hfi1_user_exp_rcv_clear(struct hfi1_filedata *fd,
                            struct hfi1_tid_info *tinfo)
{
        int ret = 0;
        struct hfi1_ctxtdata *uctxt = fd->uctxt;
        u32 *tidinfo;
        unsigned tididx;

        if (unlikely(tinfo->tidcnt > fd->tid_used))
                return -EINVAL;

        tidinfo = memdup_user(u64_to_user_ptr(tinfo->tidlist),
                              sizeof(tidinfo[0]) * tinfo->tidcnt);
        if (IS_ERR(tidinfo))
                return PTR_ERR(tidinfo);

        mutex_lock(&uctxt->exp_mutex);
        for (tididx = 0; tididx < tinfo->tidcnt; tididx++) {
                ret = unprogram_rcvarray(fd, tidinfo[tididx], NULL);
                if (ret) {
                        hfi1_cdbg(TID, "Failed to unprogram rcv array %d",
                                  ret);
                        break;
                }
        }
        spin_lock(&fd->tid_lock);
        fd->tid_used -= tididx;
        spin_unlock(&fd->tid_lock);
        tinfo->tidcnt = tididx;
        mutex_unlock(&uctxt->exp_mutex);

        kfree(tidinfo);
        return ret;
}

int hfi1_user_exp_rcv_invalid(struct hfi1_filedata *fd,
                              struct hfi1_tid_info *tinfo)
{
        struct hfi1_ctxtdata *uctxt = fd->uctxt;
        unsigned long *ev = uctxt->dd->events +
                (uctxt_offset(uctxt) + fd->subctxt);
        u32 *array;
        int ret = 0;

        /*
         * copy_to_user() can sleep, which will leave the invalid_lock
         * locked and cause the MMU notifier to be blocked on the lock
         * for a long time.
         * Copy the data to a local buffer so we can release the lock.
         */
        array = kcalloc(uctxt->expected_count, sizeof(*array), GFP_KERNEL);
        if (!array)
                return -EFAULT;

        spin_lock(&fd->invalid_lock);
        if (fd->invalid_tid_idx) {
                memcpy(array, fd->invalid_tids, sizeof(*array) *
                       fd->invalid_tid_idx);
                memset(fd->invalid_tids, 0, sizeof(*fd->invalid_tids) *
                       fd->invalid_tid_idx);
                tinfo->tidcnt = fd->invalid_tid_idx;
                fd->invalid_tid_idx = 0;
                /*
                 * Reset the user flag while still holding the lock.
                 * Otherwise, PSM can miss events.
                 */
                clear_bit(_HFI1_EVENT_TID_MMU_NOTIFY_BIT, ev);
        } else {
                tinfo->tidcnt = 0;
        }
        spin_unlock(&fd->invalid_lock);

        if (tinfo->tidcnt) {
                if (copy_to_user((void __user *)tinfo->tidlist,
                                 array, sizeof(*array) * tinfo->tidcnt))
                        ret = -EFAULT;
        }
        kfree(array);

        return ret;
}

static u32 find_phys_blocks(struct tid_user_buf *tidbuf, unsigned int npages)
{
        unsigned pagecount, pageidx, setcount = 0, i;
        unsigned long pfn, this_pfn;
        struct page **pages = tidbuf->pages;
        struct tid_pageset *list = tidbuf->psets;

        if (!npages)
                return 0;

        /*
         * Look for sets of physically contiguous pages in the user buffer.
         * This will allow us to optimize Expected RcvArray entry usage by
         * using the bigger supported sizes.
         */
        pfn = page_to_pfn(pages[0]);
        for (pageidx = 0, pagecount = 1, i = 1; i <= npages; i++) {
                this_pfn = i < npages ? page_to_pfn(pages[i]) : 0;

                /*
                 * If the pfn's are not sequential, pages are not physically
                 * contiguous.
                 */
                if (this_pfn != ++pfn) {
                        /*
                         * At this point we have to loop over the set of
                         * physically contiguous pages and break them down it
                         * sizes supported by the HW.
                         * There are two main constraints:
                         *     1. The max buffer size is MAX_EXPECTED_BUFFER.
                         *        If the total set size is bigger than that
                         *        program only a MAX_EXPECTED_BUFFER chunk.
                         *     2. The buffer size has to be a power of two. If
                         *        it is not, round down to the closes power of
                         *        2 and program that size.
                         */
                        while (pagecount) {
                                int maxpages = pagecount;
                                u32 bufsize = pagecount * PAGE_SIZE;

                                if (bufsize > MAX_EXPECTED_BUFFER)
                                        maxpages =
                                                MAX_EXPECTED_BUFFER >>
                                                PAGE_SHIFT;
                                else if (!is_power_of_2(bufsize))
                                        maxpages =
                                                rounddown_pow_of_two(bufsize) >>
                                                PAGE_SHIFT;

                                list[setcount].idx = pageidx;
                                list[setcount].count = maxpages;
                                pagecount -= maxpages;
                                pageidx += maxpages;
                                setcount++;
                        }
                        pageidx = i;
                        pagecount = 1;
                        pfn = this_pfn;
                } else {
                        pagecount++;
                }
        }
        return setcount;
}

/**
 * program_rcvarray() - program an RcvArray group with receive buffers
 * @fd: filedata pointer
 * @tbuf: pointer to struct tid_user_buf that has the user buffer starting
 *        virtual address, buffer length, page pointers, pagesets (array of
 *        struct tid_pageset holding information on physically contiguous
 *        chunks from the user buffer), and other fields.
 * @grp: RcvArray group
 * @start: starting index into sets array
 * @count: number of struct tid_pageset's to program
 * @tidlist: the array of u32 elements when the information about the
 *           programmed RcvArray entries is to be encoded.
 * @tididx: starting offset into tidlist
 * @pmapped: (output parameter) number of pages programmed into the RcvArray
 *           entries.
 *
 * This function will program up to 'count' number of RcvArray entries from the
 * group 'grp'. To make best use of write-combining writes, the function will
 * perform writes to the unused RcvArray entries which will be ignored by the
 * HW. Each RcvArray entry will be programmed with a physically contiguous
 * buffer chunk from the user's virtual buffer.
 *
 * Return:
 * -EINVAL if the requested count is larger than the size of the group,
 * -ENOMEM or -EFAULT on error from set_rcvarray_entry(), or
 * number of RcvArray entries programmed.
 */
static int program_rcvarray(struct hfi1_filedata *fd, struct tid_user_buf *tbuf,
                            struct tid_group *grp,
                            unsigned int start, u16 count,
                            u32 *tidlist, unsigned int *tididx,
                            unsigned int *pmapped)
{
        struct hfi1_ctxtdata *uctxt = fd->uctxt;
        struct hfi1_devdata *dd = uctxt->dd;
        u16 idx;
        u32 tidinfo = 0, rcventry, useidx = 0;
        int mapped = 0;

        /* Count should never be larger than the group size */
        if (count > grp->size)
                return -EINVAL;

        /* Find the first unused entry in the group */
        for (idx = 0; idx < grp->size; idx++) {
                if (!(grp->map & (1 << idx))) {
                        useidx = idx;
                        break;
                }
                rcv_array_wc_fill(dd, grp->base + idx);
        }

        idx = 0;
        while (idx < count) {
                u16 npages, pageidx, setidx = start + idx;
                int ret = 0;

                /*
                 * If this entry in the group is used, move to the next one.
                 * If we go past the end of the group, exit the loop.
                 */
                if (useidx >= grp->size) {
                        break;
                } else if (grp->map & (1 << useidx)) {
                        rcv_array_wc_fill(dd, grp->base + useidx);
                        useidx++;
                        continue;
                }

                rcventry = grp->base + useidx;
                npages = tbuf->psets[setidx].count;
                pageidx = tbuf->psets[setidx].idx;

                ret = set_rcvarray_entry(fd, tbuf,
                                         rcventry, grp, pageidx,
                                         npages);
                if (ret)
                        return ret;
                mapped += npages;

                tidinfo = rcventry2tidinfo(rcventry - uctxt->expected_base) |
                        EXP_TID_SET(LEN, npages);
                tidlist[(*tididx)++] = tidinfo;
                grp->used++;
                grp->map |= 1 << useidx++;
                idx++;
        }

        /* Fill the rest of the group with "blank" writes */
        for (; useidx < grp->size; useidx++)
                rcv_array_wc_fill(dd, grp->base + useidx);
        *pmapped = mapped;
        return idx;
}

static int set_rcvarray_entry(struct hfi1_filedata *fd,
                              struct tid_user_buf *tbuf,
                              u32 rcventry, struct tid_group *grp,
                              u16 pageidx, unsigned int npages)
{
        int ret;
        struct hfi1_ctxtdata *uctxt = fd->uctxt;
        struct tid_rb_node *node;
        struct hfi1_devdata *dd = uctxt->dd;
        dma_addr_t phys;
        struct page **pages = tbuf->pages + pageidx;

        /*
         * Allocate the node first so we can handle a potential
         * failure before we've programmed anything.
         */
        node = kzalloc(sizeof(*node) + (sizeof(struct page *) * npages),
                       GFP_KERNEL);
        if (!node)
                return -ENOMEM;

        phys = pci_map_single(dd->pcidev,
                              __va(page_to_phys(pages[0])),
                              npages * PAGE_SIZE, PCI_DMA_FROMDEVICE);
        if (dma_mapping_error(&dd->pcidev->dev, phys)) {
                dd_dev_err(dd, "Failed to DMA map Exp Rcv pages 0x%llx\n",
                           phys);
                kfree(node);
                return -EFAULT;
        }

        node->fdata = fd;
        node->phys = page_to_phys(pages[0]);
        node->npages = npages;
        node->rcventry = rcventry;
        node->dma_addr = phys;
        node->grp = grp;
        node->freed = false;
        memcpy(node->pages, pages, sizeof(struct page *) * npages);

        if (fd->use_mn) {
                ret = mmu_interval_notifier_insert(
                        &node->notifier, current->mm,
                        tbuf->vaddr + (pageidx * PAGE_SIZE), npages * PAGE_SIZE,
                        &tid_mn_ops);
                if (ret)
                        goto out_unmap;
                /*
                 * FIXME: This is in the wrong order, the notifier should be
                 * established before the pages are pinned by pin_rcv_pages.
                 */
                mmu_interval_read_begin(&node->notifier);
        }
        fd->entry_to_rb[node->rcventry - uctxt->expected_base] = node;

        hfi1_put_tid(dd, rcventry, PT_EXPECTED, phys, ilog2(npages) + 1);
        trace_hfi1_exp_tid_reg(uctxt->ctxt, fd->subctxt, rcventry, npages,
                               node->notifier.interval_tree.start, node->phys,
                               phys);
        return 0;

out_unmap:
        hfi1_cdbg(TID, "Failed to insert RB node %u 0x%lx, 0x%lx %d",
                  node->rcventry, node->notifier.interval_tree.start,
                  node->phys, ret);
        pci_unmap_single(dd->pcidev, phys, npages * PAGE_SIZE,
                         PCI_DMA_FROMDEVICE);
        kfree(node);
        return -EFAULT;
}

static int unprogram_rcvarray(struct hfi1_filedata *fd, u32 tidinfo,
                              struct tid_group **grp)
{
        struct hfi1_ctxtdata *uctxt = fd->uctxt;
        struct hfi1_devdata *dd = uctxt->dd;
        struct tid_rb_node *node;
        u8 tidctrl = EXP_TID_GET(tidinfo, CTRL);
        u32 tididx = EXP_TID_GET(tidinfo, IDX) << 1, rcventry;

        if (tididx >= uctxt->expected_count) {
                dd_dev_err(dd, "Invalid RcvArray entry (%u) index for ctxt %u\n",
                           tididx, uctxt->ctxt);
                return -EINVAL;
        }

        if (tidctrl == 0x3)
                return -EINVAL;

        rcventry = tididx + (tidctrl - 1);

        node = fd->entry_to_rb[rcventry];
        if (!node || node->rcventry != (uctxt->expected_base + rcventry))
                return -EBADF;

        if (grp)
                *grp = node->grp;

        if (fd->use_mn)
                mmu_interval_notifier_remove(&node->notifier);
        cacheless_tid_rb_remove(fd, node);

        return 0;
}

static void clear_tid_node(struct hfi1_filedata *fd, struct tid_rb_node *node)
{
        struct hfi1_ctxtdata *uctxt = fd->uctxt;
        struct hfi1_devdata *dd = uctxt->dd;

        trace_hfi1_exp_tid_unreg(uctxt->ctxt, fd->subctxt, node->rcventry,
                                 node->npages,
                                 node->notifier.interval_tree.start, node->phys,
                                 node->dma_addr);

        /*
         * Make sure device has seen the write before we unpin the
         * pages.
         */
        hfi1_put_tid(dd, node->rcventry, PT_INVALID_FLUSH, 0, 0);

        unpin_rcv_pages(fd, NULL, node, 0, node->npages, true);

        node->grp->used--;
        node->grp->map &= ~(1 << (node->rcventry - node->grp->base));

        if (node->grp->used == node->grp->size - 1)
                tid_group_move(node->grp, &uctxt->tid_full_list,
                               &uctxt->tid_used_list);
        else if (!node->grp->used)
                tid_group_move(node->grp, &uctxt->tid_used_list,
                               &uctxt->tid_group_list);
        kfree(node);
}

/*
 * As a simple helper for hfi1_user_exp_rcv_free, this function deals with
 * clearing nodes in the non-cached case.
 */
static void unlock_exp_tids(struct hfi1_ctxtdata *uctxt,
                            struct exp_tid_set *set,
                            struct hfi1_filedata *fd)
{
        struct tid_group *grp, *ptr;
        int i;

        list_for_each_entry_safe(grp, ptr, &set->list, list) {
                list_del_init(&grp->list);

                for (i = 0; i < grp->size; i++) {
                        if (grp->map & (1 << i)) {
                                u16 rcventry = grp->base + i;
                                struct tid_rb_node *node;

                                node = fd->entry_to_rb[rcventry -
                                                          uctxt->expected_base];
                                if (!node || node->rcventry != rcventry)
                                        continue;

                                if (fd->use_mn)
                                        mmu_interval_notifier_remove(
                                                &node->notifier);
                                cacheless_tid_rb_remove(fd, node);
                        }
                }
        }
}

static bool tid_rb_invalidate(struct mmu_interval_notifier *mni,
                              const struct mmu_notifier_range *range,
                              unsigned long cur_seq)
{
        struct tid_rb_node *node =
                container_of(mni, struct tid_rb_node, notifier);
        struct hfi1_filedata *fdata = node->fdata;
        struct hfi1_ctxtdata *uctxt = fdata->uctxt;

        if (node->freed)
                return true;

        trace_hfi1_exp_tid_inval(uctxt->ctxt, fdata->subctxt,
                                 node->notifier.interval_tree.start,
                                 node->rcventry, node->npages, node->dma_addr);
        node->freed = true;

        spin_lock(&fdata->invalid_lock);
        if (fdata->invalid_tid_idx < uctxt->expected_count) {
                fdata->invalid_tids[fdata->invalid_tid_idx] =
                        rcventry2tidinfo(node->rcventry - uctxt->expected_base);
                fdata->invalid_tids[fdata->invalid_tid_idx] |=
                        EXP_TID_SET(LEN, node->npages);
                if (!fdata->invalid_tid_idx) {
                        unsigned long *ev;

                        /*
                         * hfi1_set_uevent_bits() sets a user event flag
                         * for all processes. Because calling into the
                         * driver to process TID cache invalidations is
                         * expensive and TID cache invalidations are
                         * handled on a per-process basis, we can
                         * optimize this to set the flag only for the
                         * process in question.
                         */
                        ev = uctxt->dd->events +
                                (uctxt_offset(uctxt) + fdata->subctxt);
                        set_bit(_HFI1_EVENT_TID_MMU_NOTIFY_BIT, ev);
                }
                fdata->invalid_tid_idx++;
        }
        spin_unlock(&fdata->invalid_lock);
        return true;
}

static void cacheless_tid_rb_remove(struct hfi1_filedata *fdata,
                                    struct tid_rb_node *tnode)
{
        u32 base = fdata->uctxt->expected_base;

        fdata->entry_to_rb[tnode->rcventry - base] = NULL;
        clear_tid_node(fdata, tnode);
}