/*      $OpenBSD: bus_dma.c,v 1.60 2025/03/13 13:24:04 bluhm Exp $      */
/*      $NetBSD: bus_dma.c,v 1.3 2003/05/07 21:33:58 fvdl Exp $ */

/*-
 * Copyright (c) 1996, 1997, 1998 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Charles M. Hannum and by Jason R. Thorpe of the Numerical Aerospace
 * Simulation Facility, NASA Ames Research Center.
 *
 * 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.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

/*
 * The following is included because _bus_dma_uiomove is derived from
 * uiomove() in kern_subr.c.
 */

/*
 * Copyright (c) 1982, 1986, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Copyright (c) 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This software was developed by the Computer Systems Engineering group
 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
 * contributed to Berkeley.
 *
 * All advertising materials mentioning features or use of this software
 * must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Lawrence Berkeley Laboratory.
 *
 * 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.
 * 2. 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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/malloc.h>
#include <sys/mbuf.h>
#include <sys/proc.h>

#include <machine/bus.h>

#include <uvm/uvm_extern.h>

/* #define FORCE_BOUNCE_BUFFER  1 */
#ifndef FORCE_BOUNCE_BUFFER
#define FORCE_BOUNCE_BUFFER     0
#endif

int _bus_dmamap_load_buffer(bus_dma_tag_t, bus_dmamap_t, void *, bus_size_t,
    struct proc *, int, paddr_t *, int *, int *, int);

/*
 * Common function for DMA map creation.  May be called by bus-specific
 * DMA map creation functions.
 */
int
_bus_dmamap_create(bus_dma_tag_t t, bus_size_t size, int nsegments,
    bus_size_t maxsegsz, bus_size_t boundary, int flags, bus_dmamap_t *dmamp)
{
        struct bus_dmamap *map;
        struct pglist mlist;
        struct vm_page **pg, *pgnext;
        size_t mapsize, sz, ssize;
        vaddr_t va, sva;
        void *mapstore;
        int npages, error;
        const struct kmem_dyn_mode *kd;
        /* allocate and use bounce buffers when running as SEV guest */
        int use_bounce_buffer = cpu_sev_guestmode || FORCE_BOUNCE_BUFFER;

        /*
         * Allocate and initialize the DMA map.  The end of the map
         * is a variable-sized array of segments, so we allocate enough
         * room for them in one shot.
         *
         * Note we don't preserve the WAITOK or NOWAIT flags.  Preservation
         * of ALLOCNOW notifies others that we've reserved these resources,
         * and they are not to be freed.
         *
         * The bus_dmamap_t includes one bus_dma_segment_t, hence
         * the (nsegments - 1).
         */
        mapsize = sizeof(struct bus_dmamap) +
            (sizeof(bus_dma_segment_t) * (nsegments - 1));

        if (use_bounce_buffer) {
                /* this many pages plus one in case we get split */
                npages = round_page(size) / PAGE_SIZE + 1;
                if (npages < nsegments)
                        npages = nsegments;
                mapsize += sizeof(struct vm_page *) * npages;
        }

        mapstore = malloc(mapsize, M_DEVBUF,
            (flags & BUS_DMA_NOWAIT) ? (M_NOWAIT|M_ZERO) : (M_WAITOK|M_ZERO));
        if (mapstore == NULL)
                return (ENOMEM);

        map = (struct bus_dmamap *)mapstore;
        map->_dm_size = size;
        map->_dm_segcnt = nsegments;
        map->_dm_maxsegsz = maxsegsz;
        map->_dm_boundary = boundary;
        if (use_bounce_buffer) {
                map->_dm_pages = (void *)&map->dm_segs[nsegments];
                map->_dm_npages = npages;
        }
        map->_dm_flags = flags & ~(BUS_DMA_WAITOK|BUS_DMA_NOWAIT);

        if (!use_bounce_buffer) {
                *dmamp = map;
                return (0);
        }

        sz = npages << PGSHIFT;
        kd = flags & BUS_DMA_NOWAIT ? &kd_trylock : &kd_waitok;
        va = (vaddr_t)km_alloc(sz, &kv_any, &kp_none, kd);
        if (va == 0) {
                map->_dm_npages = 0;
                free(map, M_DEVBUF, mapsize);
                return (ENOMEM);
        }

        TAILQ_INIT(&mlist);
        error = uvm_pglistalloc(sz, 0, -1, PAGE_SIZE, 0, &mlist, nsegments,
            (flags & BUS_DMA_NOWAIT) ? UVM_PLA_NOWAIT : UVM_PLA_WAITOK);
        if (error) {
                map->_dm_npages = 0;
                km_free((void *)va, sz, &kv_any, &kp_none);
                free(map, M_DEVBUF, mapsize);
                return (ENOMEM);
        }

        sva = va;
        ssize = sz;
        pgnext = TAILQ_FIRST(&mlist);
        for (pg = map->_dm_pages; npages--; va += PAGE_SIZE, pg++) {
                *pg = pgnext;
                error = pmap_enter(pmap_kernel(), va, VM_PAGE_TO_PHYS(*pg),
                    PROT_READ | PROT_WRITE,
                    PROT_READ | PROT_WRITE | PMAP_WIRED |
                    PMAP_CANFAIL | PMAP_NOCRYPT);
                if (error) {
                        pmap_update(pmap_kernel());
                        map->_dm_npages = 0;
                        km_free((void *)sva, ssize, &kv_any, &kp_none);
                        free(map, M_DEVBUF, mapsize);
                        uvm_pglistfree(&mlist);
                        return (ENOMEM);
                }
                pgnext = TAILQ_NEXT(*pg, pageq);
                bzero((void *)va, PAGE_SIZE);
        }
        pmap_update(pmap_kernel());
        map->_dm_pgva = sva;

        *dmamp = map;
        return (0);
}

/*
 * Common function for DMA map destruction.  May be called by bus-specific
 * DMA map destruction functions.
 */
void
_bus_dmamap_destroy(bus_dma_tag_t t, bus_dmamap_t map)
{
        size_t mapsize;
        struct vm_page **pg;
        struct pglist mlist;
        int use_bounce_buffer = cpu_sev_guestmode || FORCE_BOUNCE_BUFFER;

        if (map->_dm_pgva) {
                km_free((void *)map->_dm_pgva, map->_dm_npages << PGSHIFT,
                    &kv_any, &kp_none);
        }

        mapsize = sizeof(struct bus_dmamap) +
                (sizeof(bus_dma_segment_t) * (map->_dm_segcnt - 1));
        if (use_bounce_buffer)
                mapsize += sizeof(struct vm_page *) * map->_dm_npages;

        if (map->_dm_pages) {
                TAILQ_INIT(&mlist);
                for (pg = map->_dm_pages; map->_dm_npages--; pg++) {
                        TAILQ_INSERT_TAIL(&mlist, *pg, pageq);
                }
                uvm_pglistfree(&mlist);
        }

        free(map, M_DEVBUF, mapsize);
}

/*
 * Common function for loading a DMA map with a linear buffer.  May
 * be called by bus-specific DMA map load functions.
 */
int
_bus_dmamap_load(bus_dma_tag_t t, bus_dmamap_t map, void *buf,
    bus_size_t buflen, struct proc *p, int flags)
{
        bus_addr_t lastaddr = 0;
        int seg, used, error;

        /*
         * Make sure that on error condition we return "no valid mappings".
         */
        map->dm_mapsize = 0;
        map->dm_nsegs = 0;

        if (buflen > map->_dm_size)
                return (EINVAL);

        seg = 0;
        used = 0;
        error = _bus_dmamap_load_buffer(t, map, buf, buflen, p, flags,
            &lastaddr, &seg, &used, 1);
        if (error == 0) {
                map->dm_mapsize = buflen;
                map->dm_nsegs = seg + 1;
                map->_dm_nused = used;
        }
        return (error);
}

/*
 * Like _bus_dmamap_load(), but for mbufs.
 */
int
_bus_dmamap_load_mbuf(bus_dma_tag_t t, bus_dmamap_t map, struct mbuf *m0,
    int flags)
{
        paddr_t lastaddr = 0;
        int seg, used, error, first;
        struct mbuf *m;

        /*
         * Make sure that on error condition we return "no valid mappings".
         */
        map->dm_mapsize = 0;
        map->dm_nsegs = 0;

#ifdef DIAGNOSTIC
        if ((m0->m_flags & M_PKTHDR) == 0)
                panic("_bus_dmamap_load_mbuf: no packet header");
#endif

        if (m0->m_pkthdr.len > map->_dm_size)
                return (EINVAL);

        first = 1;
        seg = 0;
        used = 0;
        error = 0;
        for (m = m0; m != NULL && error == 0; m = m->m_next) {
                if (m->m_len == 0)
                        continue;
                error = _bus_dmamap_load_buffer(t, map, m->m_data, m->m_len,
                    NULL, flags, &lastaddr, &seg, &used, first);
                first = 0;
        }
        if (error == 0) {
                map->dm_mapsize = m0->m_pkthdr.len;
                map->dm_nsegs = seg + 1;
                map->_dm_nused = used;
        }
        return (error);
}

/*
 * Like _bus_dmamap_load(), but for uios.
 */
int
_bus_dmamap_load_uio(bus_dma_tag_t t, bus_dmamap_t map, struct uio *uio,
    int flags)
{
        paddr_t lastaddr = 0;
        int seg, used, i, error, first;
        bus_size_t minlen, resid;
        struct proc *p = NULL;
        struct iovec *iov;
        caddr_t addr;

        /*
         * Make sure that on error condition we return "no valid mappings".
         */
        map->dm_mapsize = 0;
        map->dm_nsegs = 0;

        resid = uio->uio_resid;
        iov = uio->uio_iov;

        if (uio->uio_segflg == UIO_USERSPACE) {
                p = uio->uio_procp;
#ifdef DIAGNOSTIC
                if (p == NULL)
                        panic("_bus_dmamap_load_uio: USERSPACE but no proc");
#endif
        }

        first = 1;
        seg = 0;
        used = 0;
        error = 0;
        for (i = 0; i < uio->uio_iovcnt && resid != 0 && error == 0; i++) {
                /*
                 * Now at the first iovec to load.  Load each iovec
                 * until we have exhausted the residual count.
                 */
                minlen = resid < iov[i].iov_len ? resid : iov[i].iov_len;
                addr = (caddr_t)iov[i].iov_base;

                error = _bus_dmamap_load_buffer(t, map, addr, minlen,
                    p, flags, &lastaddr, &seg, &used, first);
                first = 0;

                resid -= minlen;
        }
        if (error == 0) {
                map->dm_mapsize = uio->uio_resid;
                map->dm_nsegs = seg + 1;
                map->_dm_nused = used;
        }
        return (error);
}

/*
 * Like _bus_dmamap_load(), but for raw memory allocated with
 * bus_dmamem_alloc().
 */
int
_bus_dmamap_load_raw(bus_dma_tag_t t, bus_dmamap_t map, bus_dma_segment_t *segs,
    int nsegs, bus_size_t size, int flags)
{
        bus_addr_t paddr, baddr, bmask, lastaddr = 0;
        bus_size_t plen, sgsize, mapsize;
        int first = 1;
        int i, seg = 0;
        int page, off;
        vaddr_t pgva, vaddr;
        int use_bounce_buffer = cpu_sev_guestmode || FORCE_BOUNCE_BUFFER;

        /*
         * Make sure that on error condition we return "no valid mappings".
         */
        map->dm_mapsize = 0;
        map->dm_nsegs = 0;

        if (nsegs > map->_dm_segcnt || size > map->_dm_size)
                return (EINVAL);

        page = 0;
        pgva = -1;
        vaddr = -1;

        mapsize = size;
        bmask  = ~(map->_dm_boundary - 1);

        for (i = 0; i < nsegs && size > 0; i++) {
                paddr = segs[i].ds_addr;
                plen = MIN(segs[i].ds_len, size);

                while (plen > 0) {
                        if (use_bounce_buffer) {
                                if (page >= map->_dm_npages)
                                        return (EFBIG);

                                off = paddr & PAGE_MASK;
                                vaddr = PMAP_DIRECT_MAP(paddr);
                                pgva = map->_dm_pgva + (page << PGSHIFT) + off;
                                page++;
                        }

                        /*
                         * Compute the segment size, and adjust counts.
                         */
                        sgsize = PAGE_SIZE - ((u_long)paddr & PGOFSET);
                        if (plen < sgsize)
                                sgsize = plen;

                        if (paddr > dma_constraint.ucr_high &&
                            (map->_dm_flags & BUS_DMA_64BIT) == 0)
                                panic("Non dma-reachable buffer at "
                                    "paddr %#lx(raw)", paddr);

                        /*
                         * Make sure we don't cross any boundaries.
                         */
                        if (map->_dm_boundary > 0) {
                                baddr = (paddr + map->_dm_boundary) & bmask;
                                if (sgsize > (baddr - paddr))
                                        sgsize = (baddr - paddr);
                        }

                        /*
                         * Insert chunk into a segment, coalescing with
                         * previous segment if possible.
                         */
                        if (first) {
                                map->dm_segs[seg].ds_addr = paddr;
                                map->dm_segs[seg].ds_len = sgsize;
                                map->dm_segs[seg]._ds_va = vaddr;
                                map->dm_segs[seg]._ds_bounce_va = pgva;
                                first = 0;
                        } else {
                                if (paddr == lastaddr &&
                                    (map->dm_segs[seg].ds_len + sgsize) <=
                                     map->_dm_maxsegsz &&
                                    (map->_dm_boundary == 0 ||
                                     (map->dm_segs[seg].ds_addr & bmask) ==
                                     (paddr & bmask)) &&
                                    (!use_bounce_buffer ||
                                     (map->dm_segs[seg]._ds_va +
                                     map->dm_segs[seg].ds_len) == vaddr)) {
                                        map->dm_segs[seg].ds_len += sgsize;
                                } else {
                                        if (++seg >= map->_dm_segcnt)
                                                return (EINVAL);
                                        map->dm_segs[seg].ds_addr = paddr;
                                        map->dm_segs[seg].ds_len = sgsize;
                                        map->dm_segs[seg]._ds_va = vaddr;
                                        map->dm_segs[seg]._ds_bounce_va = pgva;
                                }
                        }

                        paddr += sgsize;
                        plen -= sgsize;
                        size -= sgsize;

                        lastaddr = paddr;
                }
        }

        map->dm_mapsize = mapsize;
        map->dm_nsegs = seg + 1;
        return (0);
}

/*
 * Common function for unloading a DMA map.  May be called by
 * bus-specific DMA map unload functions.
 */
void
_bus_dmamap_unload(bus_dma_tag_t t, bus_dmamap_t map)
{
        /*
         * No resources to free; just mark the mappings as
         * invalid.
         */
        map->dm_mapsize = 0;
        map->dm_nsegs = 0;
        map->_dm_nused = 0;
}

/*
 * Common function for DMA map synchronization.  May be called
 * by bus-specific DMA map synchronization functions.
 */
void
_bus_dmamap_sync(bus_dma_tag_t t, bus_dmamap_t map, bus_addr_t addr,
    bus_size_t size, int op)
{
        bus_dma_segment_t *sg;
        int i, off = addr;
        bus_size_t l;
        int use_bounce_buffer = cpu_sev_guestmode || FORCE_BOUNCE_BUFFER;

        if (!use_bounce_buffer)
                return;

        for (i = map->_dm_segcnt, sg = map->dm_segs; size && i; i--, sg++) {
                if (off >= sg->ds_len) {
                        off -= sg->ds_len;
                        continue;
                }

                l = sg->ds_len - off;
                if (l > size)
                        l = size;
                size -= l;

                /* PREREAD and POSTWRITE are no-ops. */

                /* READ: device -> memory */
                if (op & BUS_DMASYNC_POSTREAD) {
                        bcopy((void *)(sg->_ds_bounce_va + off),
                            (void *)(sg->_ds_va + off), l);
                }

                /* WRITE: memory -> device */
                if (op & BUS_DMASYNC_PREWRITE) {
                        bcopy((void *)(sg->_ds_va + off),
                            (void *)(sg->_ds_bounce_va + off), l);
                }

                off = 0;
        }
}

/*
 * Common function for DMA-safe memory allocation.  May be called
 * by bus-specific DMA memory allocation functions.
 */
int
_bus_dmamem_alloc(bus_dma_tag_t t, bus_size_t size, bus_size_t alignment,
    bus_size_t boundary, bus_dma_segment_t *segs, int nsegs, int *rsegs,
    int flags)
{
        paddr_t low, high;

        if (flags & BUS_DMA_64BIT) {
                low = no_constraint.ucr_low;
                high = no_constraint.ucr_high;
        } else {
                low = dma_constraint.ucr_low;
                high = dma_constraint.ucr_high;
        }

        return _bus_dmamem_alloc_range(t, size, alignment, boundary,
            segs, nsegs, rsegs, flags, low, high);
}

/*
 * Common function for freeing DMA-safe memory.  May be called by
 * bus-specific DMA memory free functions.
 */
void
_bus_dmamem_free(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs)
{
        struct vm_page *m;
        bus_addr_t addr;
        struct pglist mlist;
        int curseg;

        /*
         * Build a list of pages to free back to the VM system.
         */
        TAILQ_INIT(&mlist);
        for (curseg = 0; curseg < nsegs; curseg++) {
                for (addr = segs[curseg].ds_addr;
                    addr < (segs[curseg].ds_addr + segs[curseg].ds_len);
                    addr += PAGE_SIZE) {
                        m = PHYS_TO_VM_PAGE(addr);
                        TAILQ_INSERT_TAIL(&mlist, m, pageq);
                }
        }

        uvm_pglistfree(&mlist);
}

/*
 * Common function for mapping DMA-safe memory.  May be called by
 * bus-specific DMA memory map functions.
 */
int
_bus_dmamem_map(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs,
    size_t size, caddr_t *kvap, int flags)
{
        vaddr_t va, sva;
        size_t ssize;
        bus_addr_t addr;
        int curseg, pmapflags = 0, error;
        const struct kmem_dyn_mode *kd;

        if (nsegs == 1 && (flags & BUS_DMA_NOCACHE) == 0) {
                *kvap = (caddr_t)PMAP_DIRECT_MAP(segs[0].ds_addr);
                return (0);
        }

        if (flags & BUS_DMA_NOCACHE)
                pmapflags |= PMAP_NOCACHE;

        size = round_page(size);
        kd = flags & BUS_DMA_NOWAIT ? &kd_trylock : &kd_waitok;
        va = (vaddr_t)km_alloc(size, &kv_any, &kp_none, kd);
        if (va == 0)
                return (ENOMEM);

        *kvap = (caddr_t)va;

        sva = va;
        ssize = size;
        for (curseg = 0; curseg < nsegs; curseg++) {
                for (addr = segs[curseg].ds_addr;
                    addr < (segs[curseg].ds_addr + segs[curseg].ds_len);
                    addr += PAGE_SIZE, va += PAGE_SIZE, size -= PAGE_SIZE) {
                        if (size == 0)
                                panic("_bus_dmamem_map: size botch");
                        error = pmap_enter(pmap_kernel(), va, addr | pmapflags,
                            PROT_READ | PROT_WRITE,
                            PROT_READ | PROT_WRITE | PMAP_WIRED | PMAP_CANFAIL);
                        if (error) {
                                pmap_update(pmap_kernel());
                                km_free((void *)sva, ssize, &kv_any, &kp_none);
                                return (error);
                        }
                }
        }
        pmap_update(pmap_kernel());

        return (0);
}

/*
 * Common function for unmapping DMA-safe memory.  May be called by
 * bus-specific DMA memory unmapping functions.
 */
void
_bus_dmamem_unmap(bus_dma_tag_t t, caddr_t kva, size_t size)
{

#ifdef DIAGNOSTIC
        if ((u_long)kva & PGOFSET)
                panic("_bus_dmamem_unmap");
#endif
        if (kva >= (caddr_t)PMAP_DIRECT_BASE && kva <= (caddr_t)PMAP_DIRECT_END)
                return;

        km_free(kva, round_page(size), &kv_any, &kp_none);
}

/*
 * Common function for mmap(2)'ing DMA-safe memory.  May be called by
 * bus-specific DMA mmap(2)'ing functions.
 */
paddr_t
_bus_dmamem_mmap(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs, off_t off,
    int prot, int flags)
{
        int i, pmapflags = 0;

        if (flags & BUS_DMA_NOCACHE)
                pmapflags |= PMAP_NOCACHE;

        for (i = 0; i < nsegs; i++) {
#ifdef DIAGNOSTIC
                if (off & PGOFSET)
                        panic("_bus_dmamem_mmap: offset unaligned");
                if (segs[i].ds_addr & PGOFSET)
                        panic("_bus_dmamem_mmap: segment unaligned");
                if (segs[i].ds_len & PGOFSET)
                        panic("_bus_dmamem_mmap: segment size not multiple"
                            " of page size");
#endif
                if (off >= segs[i].ds_len) {
                        off -= segs[i].ds_len;
                        continue;
                }

                return ((segs[i].ds_addr + off) | pmapflags);
        }

        /* Page not found. */
        return (-1);
}

/**********************************************************************
 * DMA utility functions
 **********************************************************************/
/*
 * Utility function to load a linear buffer.  lastaddrp holds state
 * between invocations (for multiple-buffer loads).  segp contains
 * the starting segment on entrance, and the ending segment on exit.
 * first indicates if this is the first invocation of this function.
 */
int
_bus_dmamap_load_buffer(bus_dma_tag_t t, bus_dmamap_t map, void *buf,
    bus_size_t buflen, struct proc *p, int flags, paddr_t *lastaddrp,
    int *segp, int *usedp, int first)
{
        bus_size_t sgsize;
        bus_addr_t curaddr, lastaddr, baddr, bmask;
        vaddr_t pgva = -1, vaddr = (vaddr_t)buf;
        int seg, page, off;
        pmap_t pmap;
        struct vm_page *pg;
        int use_bounce_buffer = cpu_sev_guestmode || FORCE_BOUNCE_BUFFER;

        if (p != NULL)
                pmap = p->p_vmspace->vm_map.pmap;
        else
                pmap = pmap_kernel();

        page = *usedp;
        lastaddr = *lastaddrp;
        bmask  = ~(map->_dm_boundary - 1);

        for (seg = *segp; buflen > 0 ; ) {
                /*
                 * Get the physical address for this segment.
                 */
                pmap_extract(pmap, vaddr, (paddr_t *)&curaddr);

                if (curaddr > dma_constraint.ucr_high &&
                    (map->_dm_flags & BUS_DMA_64BIT) == 0)
                        panic("Non dma-reachable buffer at curaddr %#lx(raw)",
                            curaddr);

                if (use_bounce_buffer) {
                        if (page >= map->_dm_npages)
                                return (EFBIG);

                        off = vaddr & PAGE_MASK;
                        pg = map->_dm_pages[page];
                        curaddr = VM_PAGE_TO_PHYS(pg) + off;
                        pgva = map->_dm_pgva + (page << PGSHIFT) + off;
                        page++;
                }

                /*
                 * Compute the segment size, and adjust counts.
                 */
                sgsize = PAGE_SIZE - ((u_long)vaddr & PGOFSET);
                if (buflen < sgsize)
                        sgsize = buflen;

                /*
                 * Make sure we don't cross any boundaries.
                 */
                if (map->_dm_boundary > 0) {
                        baddr = (curaddr + map->_dm_boundary) & bmask;
                        if (sgsize > (baddr - curaddr))
                                sgsize = (baddr - curaddr);
                }

                /*
                 * Insert chunk into a segment, coalescing with
                 * previous segment if possible.
                 */
                if (first) {
                        map->dm_segs[seg].ds_addr = curaddr;
                        map->dm_segs[seg].ds_len = sgsize;
                        map->dm_segs[seg]._ds_va = vaddr;
                        map->dm_segs[seg]._ds_bounce_va = pgva;
                        first = 0;
                } else {
                        if (curaddr == lastaddr &&
                            (map->dm_segs[seg].ds_len + sgsize) <=
                             map->_dm_maxsegsz &&
                            (map->_dm_boundary == 0 ||
                             (map->dm_segs[seg].ds_addr & bmask) ==
                             (curaddr & bmask)) &&
                            (!use_bounce_buffer || (map->dm_segs[seg]._ds_va +
                             map->dm_segs[seg].ds_len) == vaddr)) {
                                map->dm_segs[seg].ds_len += sgsize;
                        } else {
                                if (++seg >= map->_dm_segcnt)
                                        break;
                                map->dm_segs[seg].ds_addr = curaddr;
                                map->dm_segs[seg].ds_len = sgsize;
                                map->dm_segs[seg]._ds_va = vaddr;
                                map->dm_segs[seg]._ds_bounce_va = pgva;
                        }
                }

                lastaddr = curaddr + sgsize;
                vaddr += sgsize;
                buflen -= sgsize;
        }

        *segp = seg;
        *usedp = page;
        *lastaddrp = lastaddr;

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

/*
 * Allocate physical memory from the given physical address range.
 * Called by DMA-safe memory allocation methods.
 */
int
_bus_dmamem_alloc_range(bus_dma_tag_t t, bus_size_t size, bus_size_t alignment,
    bus_size_t boundary, bus_dma_segment_t *segs, int nsegs, int *rsegs,
    int flags, bus_addr_t low, bus_addr_t high)
{
        paddr_t curaddr, lastaddr;
        struct vm_page *m;
        struct pglist mlist;
        int curseg, error, plaflag;

        /* Always round the size. */
        size = round_page(size);

        segs[0]._ds_boundary = boundary;
        segs[0]._ds_align = alignment;

        /*
         * Allocate pages from the VM system.
         */
        plaflag = flags & BUS_DMA_NOWAIT ? UVM_PLA_NOWAIT : UVM_PLA_WAITOK;
        if (flags & BUS_DMA_ZERO)
                plaflag |= UVM_PLA_ZERO;

        TAILQ_INIT(&mlist);
        error = uvm_pglistalloc(size, low, high, alignment, boundary,
            &mlist, nsegs, plaflag);
        if (error)
                return (error);

        /*
         * Compute the location, size, and number of segments actually
         * returned by the VM code.
         */
        m = TAILQ_FIRST(&mlist);
        curseg = 0;
        lastaddr = segs[curseg].ds_addr = VM_PAGE_TO_PHYS(m);
        segs[curseg].ds_len = PAGE_SIZE;

        for (m = TAILQ_NEXT(m, pageq); m != NULL; m = TAILQ_NEXT(m, pageq)) {
                curaddr = VM_PAGE_TO_PHYS(m);
#ifdef DIAGNOSTIC
                if (curseg == nsegs) {
                        printf("uvm_pglistalloc returned too many\n");
                        panic("_bus_dmamem_alloc_range");
                }
                if (curaddr < low || curaddr >= high) {
                        printf("uvm_pglistalloc returned non-sensical"
                            " address 0x%lx\n", curaddr);
                        panic("_bus_dmamem_alloc_range");
                }
#endif
                if (curaddr == (lastaddr + PAGE_SIZE))
                        segs[curseg].ds_len += PAGE_SIZE;
                else {
                        curseg++;
                        segs[curseg].ds_addr = curaddr;
                        segs[curseg].ds_len = PAGE_SIZE;
                }
                lastaddr = curaddr;
        }

        *rsegs = curseg + 1;

        return (0);
}