/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 1997, 1998 Justin T. Gibbs.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification, immediately at the beginning of the file.
 * 2. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 <sys/param.h>
#include <sys/systm.h>
#include <sys/domainset.h>
#include <sys/malloc.h>
#include <sys/bus.h>
#include <sys/interrupt.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/proc.h>
#include <sys/memdesc.h>
#include <sys/msan.h>
#include <sys/mutex.h>
#include <sys/sysctl.h>
#include <sys/uio.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>

#include <machine/atomic.h>
#include <machine/bus.h>
#include <machine/md_var.h>
#include <machine/specialreg.h>
#include <x86/include/busdma_impl.h>

#ifdef __i386__
#define MAX_BPAGES (Maxmem > atop(0x100000000ULL) ? 8192 : 512)
#else
#define MAX_BPAGES 8192
#endif

enum {
        BUS_DMA_COULD_BOUNCE    = 0x01,
        BUS_DMA_MIN_ALLOC_COMP  = 0x02,
        BUS_DMA_KMEM_ALLOC      = 0x04,
        BUS_DMA_FORCE_MAP       = 0x08,
};

struct bounce_page;
struct bounce_zone;

struct bus_dma_tag {
        struct bus_dma_tag_common common;
        int                     map_count;
        int                     bounce_flags;
        bus_dma_segment_t       *segments;
        struct bounce_zone      *bounce_zone;
};

static SYSCTL_NODE(_hw, OID_AUTO, busdma, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
    "Busdma parameters");

struct bus_dmamap {
        STAILQ_HEAD(, bounce_page) bpages;
        int                    pagesneeded;
        int                    pagesreserved;
        bus_dma_tag_t          dmat;
        struct memdesc         mem;
        bus_dmamap_callback_t *callback;
        void                  *callback_arg;
        __sbintime_t           queued_time;
        STAILQ_ENTRY(bus_dmamap) links;
#ifdef KMSAN
        struct memdesc         kmsan_mem;
#endif
};

static struct bus_dmamap nobounce_dmamap;

static bool _bus_dmamap_pagesneeded(bus_dma_tag_t dmat, vm_paddr_t buf,
    bus_size_t buflen, int *pagesneeded);
static void _bus_dmamap_count_pages(bus_dma_tag_t dmat, bus_dmamap_t map,
    pmap_t pmap, void *buf, bus_size_t buflen, int flags);
static void _bus_dmamap_count_phys(bus_dma_tag_t dmat, bus_dmamap_t map,
    vm_paddr_t buf, bus_size_t buflen, int flags);

static MALLOC_DEFINE(M_BUSDMA, "busdma", "busdma metadata");

#define dmat_alignment(dmat)    ((dmat)->common.alignment)
#define dmat_bounce_flags(dmat) ((dmat)->bounce_flags)
#define dmat_boundary(dmat)     ((dmat)->common.boundary)
#define dmat_domain(dmat)       ((dmat)->common.domain)
#define dmat_flags(dmat)        ((dmat)->common.flags)
#define dmat_highaddr(dmat)     ((dmat)->common.highaddr)
#define dmat_lowaddr(dmat)      ((dmat)->common.lowaddr)
#define dmat_lockfunc(dmat)     ((dmat)->common.lockfunc)
#define dmat_lockfuncarg(dmat)  ((dmat)->common.lockfuncarg)
#define dmat_maxsegsz(dmat)     ((dmat)->common.maxsegsz)
#define dmat_nsegments(dmat)    ((dmat)->common.nsegments)

#include "../../kern/subr_busdma_bounce.c"

/*
 * On i386 kernels without 'options PAE' we need to also bounce any
 * physical addresses above 4G.
 *
 * NB: vm_paddr_t is required here since bus_addr_t is only 32 bits in
 * i386 kernels without 'options PAE'.
 */
static __inline bool
must_bounce(bus_dma_tag_t dmat, vm_paddr_t paddr)
{
#if defined(__i386__) && !defined(PAE)
        if (paddr > BUS_SPACE_MAXADDR)
                return (true);
#endif
        return (addr_needs_bounce(dmat, paddr));
}

static int
bounce_bus_dma_zone_setup(bus_dma_tag_t dmat)
{
        struct bounce_zone *bz;
        int error;

        /* Must bounce */
        if ((error = alloc_bounce_zone(dmat)) != 0)
                return (error);
        bz = dmat->bounce_zone;

        if (ptoa(bz->total_bpages) < dmat->common.maxsize) {
                int pages;

                pages = atop(dmat->common.maxsize) - bz->total_bpages;

                /* Add pages to our bounce pool */
                if (alloc_bounce_pages(dmat, pages) < pages)
                        return (ENOMEM);
        }
        /* Performed initial allocation */
        dmat->bounce_flags |= BUS_DMA_MIN_ALLOC_COMP;

        return (0);
}

/*
 * Allocate a device specific dma_tag.
 */
static int
bounce_bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
    bus_addr_t boundary, bus_addr_t lowaddr, bus_addr_t highaddr,
    bus_size_t maxsize, int nsegments, bus_size_t maxsegsz, int flags,
    bus_dma_lock_t *lockfunc, void *lockfuncarg, bus_dma_tag_t *dmat)
{
        bus_dma_tag_t newtag;
        int error;

        *dmat = NULL;
        error = common_bus_dma_tag_create(parent != NULL ? &parent->common :
            NULL, alignment, boundary, lowaddr, highaddr, maxsize, nsegments,
            maxsegsz, flags, lockfunc, lockfuncarg, sizeof(struct bus_dma_tag),
            (void **)&newtag);
        if (error != 0)
                return (error);

        newtag->common.impl = &bus_dma_bounce_impl;
        newtag->map_count = 0;
        newtag->segments = NULL;

#ifdef KMSAN
        /*
         * When KMSAN is configured, we need a map to store a memory descriptor
         * which can be used for validation.
         */
        newtag->bounce_flags |= BUS_DMA_FORCE_MAP;
#endif

        if (parent != NULL &&
            (parent->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0)
                newtag->bounce_flags |= BUS_DMA_COULD_BOUNCE;

        if (newtag->common.lowaddr < ptoa((vm_paddr_t)Maxmem) ||
            newtag->common.alignment > 1)
                newtag->bounce_flags |= BUS_DMA_COULD_BOUNCE;

        if ((newtag->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0 &&
            (flags & BUS_DMA_ALLOCNOW) != 0)
                error = bounce_bus_dma_zone_setup(newtag);
        else
                error = 0;

        if (error != 0)
                free(newtag, M_DEVBUF);
        else
                *dmat = newtag;
        CTR4(KTR_BUSDMA, "%s returned tag %p tag flags 0x%x error %d",
            __func__, newtag, (newtag != NULL ? newtag->common.flags : 0),
            error);
        return (error);
}

static bool
bounce_bus_dma_id_mapped(bus_dma_tag_t dmat, vm_paddr_t buf, bus_size_t buflen)
{

        if ((dmat->bounce_flags & BUS_DMA_COULD_BOUNCE) == 0)
                return (true);
        return (!_bus_dmamap_pagesneeded(dmat, buf, buflen, NULL));
}

/*
 * Update the domain for the tag.  We may need to reallocate the zone and
 * bounce pages.
 */ 
static int
bounce_bus_dma_tag_set_domain(bus_dma_tag_t dmat)
{

        KASSERT(dmat->map_count == 0,
            ("bounce_bus_dma_tag_set_domain:  Domain set after use.\n"));
        if ((dmat->bounce_flags & BUS_DMA_COULD_BOUNCE) == 0 ||
            dmat->bounce_zone == NULL)
                return (0);
        dmat->bounce_flags &= ~BUS_DMA_MIN_ALLOC_COMP;
        return (bounce_bus_dma_zone_setup(dmat));
}

static int
bounce_bus_dma_tag_destroy(bus_dma_tag_t dmat)
{
        int error = 0;

        if (dmat != NULL) {
                if (dmat->map_count != 0) {
                        error = EBUSY;
                        goto out;
                }
                if (dmat->segments != NULL)
                        free(dmat->segments, M_DEVBUF);
                free(dmat, M_DEVBUF);
        }
out:
        CTR3(KTR_BUSDMA, "%s tag %p error %d", __func__, dmat, error);
        return (error);
}

/*
 * Allocate a handle for mapping from kva/uva/physical
 * address space into bus device space.
 */
static int
bounce_bus_dmamap_create(bus_dma_tag_t dmat, int flags, bus_dmamap_t *mapp)
{
        struct bounce_zone *bz;
        int error, maxpages, pages;

        error = 0;

        if (dmat->segments == NULL) {
                dmat->segments = malloc_domainset(
                    sizeof(bus_dma_segment_t) * dmat->common.nsegments,
                    M_DEVBUF, DOMAINSET_PREF(dmat->common.domain), M_NOWAIT);
                if (dmat->segments == NULL) {
                        CTR3(KTR_BUSDMA, "%s: tag %p error %d",
                            __func__, dmat, ENOMEM);
                        return (ENOMEM);
                }
        }

        if (dmat->bounce_flags & (BUS_DMA_COULD_BOUNCE | BUS_DMA_FORCE_MAP)) {
                *mapp = malloc_domainset(sizeof(**mapp), M_DEVBUF,
                    DOMAINSET_PREF(dmat->common.domain), M_NOWAIT | M_ZERO);
                if (*mapp == NULL) {
                        CTR3(KTR_BUSDMA, "%s: tag %p error %d",
                            __func__, dmat, ENOMEM);
                        return (ENOMEM);
                }
                STAILQ_INIT(&(*mapp)->bpages);
        } else {
                *mapp = NULL;
        }

        /*
         * Bouncing might be required if the driver asks for an active
         * exclusion region, a data alignment that is stricter than 1, and/or
         * an active address boundary.
         */
        if ((dmat->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0) {
                /* Must bounce */
                if (dmat->bounce_zone == NULL &&
                    (error = alloc_bounce_zone(dmat)) != 0)
                        goto out;
                bz = dmat->bounce_zone;

                /*
                 * Attempt to add pages to our pool on a per-instance
                 * basis up to a sane limit.
                 */
                if (dmat->common.alignment > 1)
                        maxpages = MAX_BPAGES;
                else
                        maxpages = MIN(MAX_BPAGES, Maxmem -
                            atop(dmat->common.lowaddr));
                if ((dmat->bounce_flags & BUS_DMA_MIN_ALLOC_COMP) == 0 ||
                    (bz->map_count > 0 && bz->total_bpages < maxpages)) {
                        pages = MAX(atop(dmat->common.maxsize), 1);
                        pages = MIN(dmat->common.nsegments, pages);
                        pages = MIN(maxpages - bz->total_bpages, pages);
                        pages = MAX(pages, 1);
                        if (alloc_bounce_pages(dmat, pages) < pages)
                                error = ENOMEM;
                        if ((dmat->bounce_flags & BUS_DMA_MIN_ALLOC_COMP)
                            == 0) {
                                if (error == 0) {
                                        dmat->bounce_flags |=
                                            BUS_DMA_MIN_ALLOC_COMP;
                                }
                        } else
                                error = 0;
                }
                bz->map_count++;
        }

out:
        if (error == 0) {
                dmat->map_count++;
        } else {
                free(*mapp, M_DEVBUF);
                *mapp = NULL;
        }

        CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
            __func__, dmat, dmat->common.flags, error);
        return (error);
}

/*
 * Destroy a handle for mapping from kva/uva/physical
 * address space into bus device space.
 */
static int
bounce_bus_dmamap_destroy(bus_dma_tag_t dmat, bus_dmamap_t map)
{

        if (map != NULL && map != &nobounce_dmamap) {
                if (STAILQ_FIRST(&map->bpages) != NULL) {
                        CTR3(KTR_BUSDMA, "%s: tag %p error %d",
                            __func__, dmat, EBUSY);
                        return (EBUSY);
                }
                if (dmat->bounce_zone)
                        dmat->bounce_zone->map_count--;
                free(map, M_DEVBUF);
        }
        dmat->map_count--;
        CTR2(KTR_BUSDMA, "%s: tag %p error 0", __func__, dmat);
        return (0);
}

/*
 * Allocate a piece of memory that can be efficiently mapped into
 * bus device space based on the constraints lited in the dma tag.
 * A dmamap to for use with dmamap_load is also allocated.
 */
static int
bounce_bus_dmamem_alloc(bus_dma_tag_t dmat, void **vaddr, int flags,
    bus_dmamap_t *mapp)
{
        vm_memattr_t attr;
        int mflags;

        if (flags & BUS_DMA_NOWAIT)
                mflags = M_NOWAIT;
        else
                mflags = M_WAITOK;

        /* If we succeed, no mapping/bouncing will be required */
        *mapp = NULL;

        if (dmat->segments == NULL) {
                dmat->segments = (bus_dma_segment_t *)malloc_domainset(
                    sizeof(bus_dma_segment_t) * dmat->common.nsegments,
                    M_DEVBUF, DOMAINSET_PREF(dmat->common.domain), mflags);
                if (dmat->segments == NULL) {
                        CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
                            __func__, dmat, dmat->common.flags, ENOMEM);
                        return (ENOMEM);
                }
        }
        if (flags & BUS_DMA_ZERO)
                mflags |= M_ZERO;
        if (flags & BUS_DMA_NOCACHE)
                attr = VM_MEMATTR_UNCACHEABLE;
        else
                attr = VM_MEMATTR_DEFAULT;

        /*
         * Allocate the buffer from the malloc(9) allocator if...
         *  - It's small enough to fit into a single page.
         *  - Its alignment requirement is also smaller than the page size.
         *  - The low address requirement is fulfilled.
         *  - Default cache attributes are requested (WB).
         * else allocate non-contiguous pages if...
         *  - The page count that could get allocated doesn't exceed
         *    nsegments also when the maximum segment size is less
         *    than PAGE_SIZE.
         *  - The alignment constraint isn't larger than a page boundary.
         *  - There are no boundary-crossing constraints.
         * else allocate a block of contiguous pages because one or more of the
         * constraints is something that only the contig allocator can fulfill.
         *
         * Warn the user if malloc gets it wrong.
         */
        if (dmat->common.maxsize <= PAGE_SIZE &&
            dmat->common.alignment <= PAGE_SIZE &&
            dmat->common.lowaddr >= ptoa((vm_paddr_t)Maxmem) &&
            attr == VM_MEMATTR_DEFAULT) {
                *vaddr = malloc_domainset_aligned(dmat->common.maxsize,
                    dmat->common.alignment, M_DEVBUF,
                    DOMAINSET_PREF(dmat->common.domain), mflags);
                KASSERT(*vaddr == NULL || ((uintptr_t)*vaddr & PAGE_MASK) +
                    dmat->common.maxsize <= PAGE_SIZE,
                    ("bounce_bus_dmamem_alloc: multi-page alloc %p maxsize "
                    "%#jx align %#jx", *vaddr, (uintmax_t)dmat->common.maxsize,
                    (uintmax_t)dmat->common.alignment));
        } else if (dmat->common.nsegments >=
            howmany(dmat->common.maxsize, MIN(dmat->common.maxsegsz,
            PAGE_SIZE)) &&
            dmat->common.alignment <= PAGE_SIZE &&
            (dmat->common.boundary % PAGE_SIZE) == 0) {
                /* Page-based multi-segment allocations allowed */
                *vaddr = kmem_alloc_attr_domainset(
                    DOMAINSET_PREF(dmat->common.domain), dmat->common.maxsize,
                    mflags, 0ul, dmat->common.lowaddr, attr);
                dmat->bounce_flags |= BUS_DMA_KMEM_ALLOC;
        } else {
                *vaddr = kmem_alloc_contig_domainset(
                    DOMAINSET_PREF(dmat->common.domain), dmat->common.maxsize,
                    mflags, 0ul, dmat->common.lowaddr,
                    dmat->common.alignment != 0 ? dmat->common.alignment : 1ul,
                    dmat->common.boundary, attr);
                dmat->bounce_flags |= BUS_DMA_KMEM_ALLOC;
        }
        if (*vaddr == NULL) {
                CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
                    __func__, dmat, dmat->common.flags, ENOMEM);
                return (ENOMEM);
        } else if (!vm_addr_align_ok(vtophys(*vaddr), dmat->common.alignment)) {
                printf("bus_dmamem_alloc failed to align memory properly.\n");
        }
        CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x error %d",
            __func__, dmat, dmat->common.flags, 0);
        return (0);
}

/*
 * Free a piece of memory and its associated dmamap, that was allocated
 * via bus_dmamem_alloc.
 */
static void
bounce_bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
{
        /*
         * dmamem does not need to be bounced, so the map should be
         * NULL and the BUS_DMA_KMEM_ALLOC flag cleared if malloc()
         * was used and set if kmem_alloc_contig() was used.
         */
        if (map != NULL)
                panic("bus_dmamem_free: Invalid map freed\n");
        if ((dmat->bounce_flags & BUS_DMA_KMEM_ALLOC) == 0)
                free(vaddr, M_DEVBUF);
        else
                kmem_free(vaddr, dmat->common.maxsize);
        CTR3(KTR_BUSDMA, "%s: tag %p flags 0x%x", __func__, dmat,
            dmat->bounce_flags);
}

static bool
_bus_dmamap_pagesneeded(bus_dma_tag_t dmat, vm_paddr_t buf, bus_size_t buflen,
    int *pagesneeded)
{
        vm_paddr_t curaddr;
        bus_size_t sgsize;
        int count;

        /*
         * Count the number of bounce pages needed in order to
         * complete this transfer
         */
        count = 0;
        curaddr = buf;
        while (buflen != 0) {
                sgsize = buflen;
                if (must_bounce(dmat, curaddr)) {
                        sgsize = MIN(sgsize,
                            PAGE_SIZE - (curaddr & PAGE_MASK));
                        if (pagesneeded == NULL)
                                return (true);
                        count++;
                }
                curaddr += sgsize;
                buflen -= sgsize;
        }

        if (pagesneeded != NULL)
                *pagesneeded = count;
        return (count != 0);
}

static void
_bus_dmamap_count_phys(bus_dma_tag_t dmat, bus_dmamap_t map, vm_paddr_t buf,
    bus_size_t buflen, int flags)
{

        if (map != &nobounce_dmamap && map->pagesneeded == 0) {
                _bus_dmamap_pagesneeded(dmat, buf, buflen, &map->pagesneeded);
                CTR1(KTR_BUSDMA, "pagesneeded= %d\n", map->pagesneeded);
        }
}

static void
_bus_dmamap_count_pages(bus_dma_tag_t dmat, bus_dmamap_t map, pmap_t pmap,
    void *buf, bus_size_t buflen, int flags)
{
        vm_offset_t vaddr;
        vm_offset_t vendaddr;
        vm_paddr_t paddr;
        bus_size_t sg_len;

        if (map != &nobounce_dmamap && map->pagesneeded == 0) {
                CTR4(KTR_BUSDMA, "lowaddr= %d Maxmem= %d, boundary= %d, "
                    "alignment= %d", dmat->common.lowaddr,
                    ptoa((vm_paddr_t)Maxmem),
                    dmat->common.boundary, dmat->common.alignment);
                CTR3(KTR_BUSDMA, "map= %p, nobouncemap= %p, pagesneeded= %d",
                    map, &nobounce_dmamap, map->pagesneeded);
                /*
                 * Count the number of bounce pages
                 * needed in order to complete this transfer
                 */
                vaddr = (vm_offset_t)buf;
                vendaddr = (vm_offset_t)buf + buflen;

                while (vaddr < vendaddr) {
                        sg_len = MIN(vendaddr - vaddr,
                            PAGE_SIZE - ((vm_offset_t)vaddr & PAGE_MASK));
                        if (pmap == kernel_pmap)
                                paddr = pmap_kextract(vaddr);
                        else
                                paddr = pmap_extract(pmap, vaddr);
                        if (must_bounce(dmat, paddr)) {
                                sg_len = roundup2(sg_len,
                                    dmat->common.alignment);
                                map->pagesneeded++;
                        }
                        vaddr += sg_len;
                }
                CTR1(KTR_BUSDMA, "pagesneeded= %d\n", map->pagesneeded);
        }
}

static void
_bus_dmamap_count_ma(bus_dma_tag_t dmat, bus_dmamap_t map, struct vm_page **ma,
    int ma_offs, bus_size_t buflen, int flags)
{
        bus_size_t sg_len;
        int page_index;
        vm_paddr_t paddr;

        if (map != &nobounce_dmamap && map->pagesneeded == 0) {
                CTR4(KTR_BUSDMA, "lowaddr= %d Maxmem= %d, boundary= %d, "
                    "alignment= %d", dmat->common.lowaddr,
                    ptoa((vm_paddr_t)Maxmem),
                    dmat->common.boundary, dmat->common.alignment);
                CTR3(KTR_BUSDMA, "map= %p, nobouncemap= %p, pagesneeded= %d",
                    map, &nobounce_dmamap, map->pagesneeded);

                /*
                 * Count the number of bounce pages
                 * needed in order to complete this transfer
                 */
                page_index = 0;
                while (buflen > 0) {
                        paddr = VM_PAGE_TO_PHYS(ma[page_index]) + ma_offs;
                        sg_len = PAGE_SIZE - ma_offs;
                        sg_len = MIN(sg_len, buflen);
                        if (must_bounce(dmat, paddr)) {
                                sg_len = roundup2(sg_len,
                                    dmat->common.alignment);
                                KASSERT(vm_addr_align_ok(sg_len,
                                    dmat->common.alignment),
                                    ("Segment size is not aligned"));
                                map->pagesneeded++;
                        }
                        if (((ma_offs + sg_len) & ~PAGE_MASK) != 0)
                                page_index++;
                        ma_offs = (ma_offs + sg_len) & PAGE_MASK;
                        KASSERT(buflen >= sg_len,
                            ("Segment length overruns original buffer"));
                        buflen -= sg_len;
                }
                CTR1(KTR_BUSDMA, "pagesneeded= %d\n", map->pagesneeded);
        }
}

/*
 * Utility function to load a physical buffer.  segp contains
 * the starting segment on entrace, and the ending segment on exit.
 */
static int
bounce_bus_dmamap_load_phys(bus_dma_tag_t dmat, bus_dmamap_t map,
    vm_paddr_t buf, bus_size_t buflen, int flags, bus_dma_segment_t *segs,
    int *segp)
{
        bus_size_t sgsize;
        vm_paddr_t curaddr;
        int error;

        if (map == NULL)
                map = &nobounce_dmamap;

        if (segs == NULL)
                segs = dmat->segments;

        if ((dmat->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0) {
                _bus_dmamap_count_phys(dmat, map, buf, buflen, flags);
                if (map->pagesneeded != 0) {
                        error = _bus_dmamap_reserve_pages(dmat, map, flags);
                        if (error)
                                return (error);
                }
        }

        while (buflen > 0) {
                curaddr = buf;
                sgsize = buflen;
                if ((dmat->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0 &&
                    map->pagesneeded != 0 &&
                    must_bounce(dmat, curaddr)) {
                        sgsize = MIN(sgsize, PAGE_SIZE - (curaddr & PAGE_MASK));
                        curaddr = add_bounce_page(dmat, map, 0, curaddr, 0,
                            sgsize);
                }

                if (!_bus_dmamap_addsegs(dmat, map, curaddr, sgsize, segs,
                    segp))
                        break;
                buf += sgsize;
                buflen -= sgsize;
        }

        /*
         * Did we fit?
         */
        return (buflen != 0 ? EFBIG : 0); /* XXX better return value here? */
}

/*
 * Utility function to load a linear buffer.  segp contains
 * the starting segment on entrace, and the ending segment on exit.
 */
static int
bounce_bus_dmamap_load_buffer(bus_dma_tag_t dmat, bus_dmamap_t map, void *buf,
    bus_size_t buflen, pmap_t pmap, int flags, bus_dma_segment_t *segs,
    int *segp)
{
        bus_size_t sgsize;
        vm_paddr_t curaddr;
        char *kvaddr, *vaddr;
        int error;

        if (map == NULL)
                map = &nobounce_dmamap;

        if (segs == NULL)
                segs = dmat->segments;

        if ((dmat->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0) {
                _bus_dmamap_count_pages(dmat, map, pmap, buf, buflen, flags);
                if (map->pagesneeded != 0) {
                        error = _bus_dmamap_reserve_pages(dmat, map, flags);
                        if (error)
                                return (error);
                }
        }

        vaddr = buf;
        while (buflen > 0) {
                /*
                 * Get the physical address for this segment.
                 */
                if (pmap == kernel_pmap) {
                        curaddr = pmap_kextract((vm_offset_t)vaddr);
                        kvaddr = vaddr;
                } else {
                        curaddr = pmap_extract(pmap, (vm_offset_t)vaddr);
                        kvaddr = NULL;
                }

                /*
                 * Compute the segment size, and adjust counts.
                 */
                sgsize = MIN(buflen, PAGE_SIZE - (curaddr & PAGE_MASK));
                if ((dmat->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0 &&
                    map->pagesneeded != 0 &&
                    must_bounce(dmat, curaddr)) {
                        sgsize = roundup2(sgsize, dmat->common.alignment);
                        sgsize = MIN(sgsize, buflen);
                        curaddr = add_bounce_page(dmat, map, kvaddr, curaddr, 0,
                            sgsize);
                }
                if (!_bus_dmamap_addsegs(dmat, map, curaddr, sgsize, segs,
                    segp))
                        break;
                vaddr += sgsize;
                buflen -= MIN(sgsize, buflen); /* avoid underflow */
        }

        /*
         * Did we fit?
         */
        return (buflen != 0 ? EFBIG : 0); /* XXX better return value here? */
}

static int
bounce_bus_dmamap_load_ma(bus_dma_tag_t dmat, bus_dmamap_t map,
    struct vm_page **ma, bus_size_t buflen, int ma_offs, int flags,
    bus_dma_segment_t *segs, int *segp)
{
        vm_paddr_t paddr, next_paddr;
        int error, page_index;
        bus_size_t sgsize;

        if (dmat->common.flags & BUS_DMA_KEEP_PG_OFFSET) {
                /*
                 * If we have to keep the offset of each page this function
                 * is not suitable, switch back to bus_dmamap_load_ma_triv
                 * which is going to do the right thing in this case.
                 */
                error = bus_dmamap_load_ma_triv(dmat, map, ma, buflen, ma_offs,
                    flags, segs, segp);
                return (error);
        }

        if (map == NULL)
                map = &nobounce_dmamap;

        if (segs == NULL)
                segs = dmat->segments;

        if ((dmat->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0) {
                _bus_dmamap_count_ma(dmat, map, ma, ma_offs, buflen, flags);
                if (map->pagesneeded != 0) {
                        error = _bus_dmamap_reserve_pages(dmat, map, flags);
                        if (error)
                                return (error);
                }
        }

        page_index = 0;
        while (buflen > 0) {
                /*
                 * Compute the segment size, and adjust counts.
                 */
                paddr = VM_PAGE_TO_PHYS(ma[page_index]) + ma_offs;
                sgsize = MIN(buflen, PAGE_SIZE - ma_offs);
                if ((dmat->bounce_flags & BUS_DMA_COULD_BOUNCE) != 0 &&
                    map->pagesneeded != 0 &&
                    must_bounce(dmat, paddr)) {
                        sgsize = roundup2(sgsize, dmat->common.alignment);
                        KASSERT(vm_addr_align_ok(sgsize,
                            dmat->common.alignment),
                            ("Segment size is not aligned"));
                        /*
                         * Check if two pages of the user provided buffer
                         * are used.
                         */
                        if ((ma_offs + sgsize) > PAGE_SIZE)
                                next_paddr =
                                    VM_PAGE_TO_PHYS(ma[page_index + 1]);
                        else
                                next_paddr = 0;
                        paddr = add_bounce_page(dmat, map, 0, paddr,
                            next_paddr, sgsize);
                }
                if (!_bus_dmamap_addsegs(dmat, map, paddr, sgsize, segs,
                    segp))
                        break;
                KASSERT(buflen >= sgsize,
                    ("Segment length overruns original buffer"));
                buflen -= MIN(sgsize, buflen); /* avoid underflow */
                if (((ma_offs + sgsize) & ~PAGE_MASK) != 0)
                        page_index++;
                ma_offs = (ma_offs + sgsize) & PAGE_MASK;
        }

        /*
         * Did we fit?
         */
        return (buflen != 0 ? EFBIG : 0); /* XXX better return value here? */
}

static void
bounce_bus_dmamap_waitok(bus_dma_tag_t dmat, bus_dmamap_t map,
    struct memdesc *mem, bus_dmamap_callback_t *callback, void *callback_arg)
{

        if (map == NULL)
                return;
        map->mem = *mem;
        map->dmat = dmat;
        map->callback = callback;
        map->callback_arg = callback_arg;
}

static bus_dma_segment_t *
bounce_bus_dmamap_complete(bus_dma_tag_t dmat, bus_dmamap_t map,
    bus_dma_segment_t *segs, int nsegs, int error)
{

        if (segs == NULL)
                segs = dmat->segments;
        return (segs);
}

/*
 * Release the mapping held by map.
 */
static void
bounce_bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map)
{
        if (map == NULL)
                return;

        free_bounce_pages(dmat, map);
}

static void
bounce_bus_dmamap_sync(bus_dma_tag_t dmat, bus_dmamap_t map,
    bus_dmasync_op_t op)
{
        struct bounce_page *bpage;
        char *datavaddr, *tempvaddr;
        bus_size_t datacount1, datacount2;

        if (map == NULL)
                goto out;
        if ((bpage = STAILQ_FIRST(&map->bpages)) == NULL)
                goto out;

        /*
         * Handle data bouncing.  We might also want to add support for
         * invalidating the caches on broken hardware.
         */
        CTR4(KTR_BUSDMA, "%s: tag %p tag flags 0x%x op 0x%x "
            "performing bounce", __func__, dmat, dmat->common.flags, op);

        if ((op & BUS_DMASYNC_PREWRITE) != 0) {
                while (bpage != NULL) {
                        tempvaddr = NULL;
                        datavaddr = bpage->datavaddr;
                        datacount1 = bpage->datacount;
                        if (datavaddr == NULL) {
                                tempvaddr =
                                    pmap_quick_enter_page(bpage->datapage[0]);
                                datavaddr = tempvaddr + bpage->dataoffs;
                                datacount1 = min(PAGE_SIZE - bpage->dataoffs,
                                    datacount1);
                        }

                        bcopy(datavaddr, bpage->vaddr, datacount1);

                        if (tempvaddr != NULL)
                                pmap_quick_remove_page(tempvaddr);

                        if (bpage->datapage[1] == 0) {
                                KASSERT(datacount1 == bpage->datacount,
                ("Mismatch between data size and provided memory space"));
                                goto next_w;
                        }

                        /*
                         * We are dealing with an unmapped buffer that expands
                         * over two pages.
                         */
                        datavaddr = pmap_quick_enter_page(bpage->datapage[1]);
                        datacount2 = bpage->datacount - datacount1;
                        bcopy(datavaddr, bpage->vaddr + datacount1, datacount2);
                        pmap_quick_remove_page(datavaddr);

next_w:
                        bpage = STAILQ_NEXT(bpage, links);
                }
                dmat->bounce_zone->total_bounced++;
        }

        if ((op & BUS_DMASYNC_POSTREAD) != 0) {
                while (bpage != NULL) {
                        tempvaddr = NULL;
                        datavaddr = bpage->datavaddr;
                        datacount1 = bpage->datacount;
                        if (datavaddr == NULL) {
                                tempvaddr =
                                    pmap_quick_enter_page(bpage->datapage[0]);
                                datavaddr = tempvaddr + bpage->dataoffs;
                                datacount1 = min(PAGE_SIZE - bpage->dataoffs,
                                    datacount1);
                        }

                        bcopy(bpage->vaddr, datavaddr, datacount1);

                        if (tempvaddr != NULL)
                                pmap_quick_remove_page(tempvaddr);

                        if (bpage->datapage[1] == 0) {
                                KASSERT(datacount1 == bpage->datacount,
                ("Mismatch between data size and provided memory space"));
                                goto next_r;
                        }

                        /*
                         * We are dealing with an unmapped buffer that expands
                         * over two pages.
                         */
                        datavaddr = pmap_quick_enter_page(bpage->datapage[1]);
                        datacount2 = bpage->datacount - datacount1;
                        bcopy(bpage->vaddr + datacount1, datavaddr, datacount2);
                        pmap_quick_remove_page(datavaddr);

next_r:
                        bpage = STAILQ_NEXT(bpage, links);
                }
                dmat->bounce_zone->total_bounced++;
        }
out:
        atomic_thread_fence_rel();
        if (map != NULL)
                kmsan_bus_dmamap_sync(&map->kmsan_mem, op);
}

#ifdef KMSAN
static void
bounce_bus_dmamap_load_kmsan(bus_dmamap_t map, struct memdesc *mem)
{
        if (map == NULL)
                return;
        memcpy(&map->kmsan_mem, mem, sizeof(map->kmsan_mem));
}
#endif

struct bus_dma_impl bus_dma_bounce_impl = {
        .tag_create = bounce_bus_dma_tag_create,
        .tag_destroy = bounce_bus_dma_tag_destroy,
        .tag_set_domain = bounce_bus_dma_tag_set_domain,
        .id_mapped = bounce_bus_dma_id_mapped,
        .map_create = bounce_bus_dmamap_create,
        .map_destroy = bounce_bus_dmamap_destroy,
        .mem_alloc = bounce_bus_dmamem_alloc,
        .mem_free = bounce_bus_dmamem_free,
        .load_phys = bounce_bus_dmamap_load_phys,
        .load_buffer = bounce_bus_dmamap_load_buffer,
        .load_ma = bounce_bus_dmamap_load_ma,
        .map_waitok = bounce_bus_dmamap_waitok,
        .map_complete = bounce_bus_dmamap_complete,
        .map_unload = bounce_bus_dmamap_unload,
        .map_sync = bounce_bus_dmamap_sync,
#ifdef KMSAN
        .load_kmsan = bounce_bus_dmamap_load_kmsan,
#endif
};