drivers/iommu/dma-iommu.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * A fairly generic DMA-API to IOMMU-API glue layer.
 *
 * Copyright (C) 2014-2015 ARM Ltd.
 *
 * based in part on arch/arm/mm/dma-mapping.c:
 * Copyright (C) 2000-2004 Russell King
 */

#include <linux/acpi_iort.h>
#include <linux/device.h>
#include <linux/dma-map-ops.h>
#include <linux/dma-iommu.h>
#include <linux/gfp.h>
#include <linux/huge_mm.h>
#include <linux/iommu.h>
#include <linux/iova.h>
#include <linux/irq.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/pci.h>
#include <linux/scatterlist.h>
#include <linux/vmalloc.h>
#include <linux/crash_dump.h>

#define DMA_IOMMU_BIT_MASK_VALUE 32

struct iommu_dma_msi_page {
    struct list_head list;
    dma_addr_t iova;
    phys_addr_t phys;
};

enum iommu_dma_cookie_type {
    IOMMU_DMA_IOVA_COOKIE,
    IOMMU_DMA_MSI_COOKIE,
};

struct iommu_dma_cookie {
    enum iommu_dma_cookie_type type;
    union {
        /* Full allocator for IOMMU_DMA_IOVA_COOKIE */
        struct iova_domain iovad;
        /* Trivial linear page allocator for IOMMU_DMA_MSI_COOKIE */
        dma_addr_t msi_iova;
    };
    struct list_head msi_page_list;

    /* Domain for flush queue callback; NULL if flush queue not in use */
    struct iommu_domain *fq_domain;
};

static inline size_t cookie_msi_granule(struct iommu_dma_cookie *cookie)
{
    if (cookie->type == IOMMU_DMA_IOVA_COOKIE) {
        return cookie->iovad.granule;
    }
    return PAGE_SIZE;
}

static struct iommu_dma_cookie *cookie_alloc(enum iommu_dma_cookie_type type)
{
    struct iommu_dma_cookie *cookie;

    cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
    if (cookie) {
        INIT_LIST_HEAD(&cookie->msi_page_list);
        cookie->type = type;
    }
    return cookie;
}

/**
 * iommu_get_dma_cookie - Acquire DMA-API resources for a domain
 * @domain: IOMMU domain to prepare for DMA-API usage
 *
 * IOMMU drivers should normally call this from their domain_alloc
 * callback when domain->type == IOMMU_DOMAIN_DMA.
 */
int iommu_get_dma_cookie(struct iommu_domain *domain)
{
    if (domain->iova_cookie) {
        return -EEXIST;
    }

    domain->iova_cookie = cookie_alloc(IOMMU_DMA_IOVA_COOKIE);
    if (!domain->iova_cookie) {
        return -ENOMEM;
    }

    return 0;
}
EXPORT_SYMBOL(iommu_get_dma_cookie);

/**
 * iommu_get_msi_cookie - Acquire just MSI remapping resources
 * @domain: IOMMU domain to prepare
 * @base: Start address of IOVA region for MSI mappings
 *
 * Users who manage their own IOVA allocation and do not want DMA API support,
 * but would still like to take advantage of automatic MSI remapping, can use
 * this to initialise their own domain appropriately. Users should reserve a
 * contiguous IOVA region, starting at @base, large enough to accommodate the
 * number of PAGE_SIZE mappings necessary to cover every MSI doorbell address
 * used by the devices attached to @domain.
 */
int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
{
    struct iommu_dma_cookie *cookie;

    if (domain->type != IOMMU_DOMAIN_UNMANAGED) {
        return -EINVAL;
    }

    if (domain->iova_cookie) {
        return -EEXIST;
    }

    cookie = cookie_alloc(IOMMU_DMA_MSI_COOKIE);
    if (!cookie) {
        return -ENOMEM;
    }

    cookie->msi_iova = base;
    domain->iova_cookie = cookie;
    return 0;
}
EXPORT_SYMBOL(iommu_get_msi_cookie);

/**
 * iommu_put_dma_cookie - Release a domain's DMA mapping resources
 * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie() or
 *          iommu_get_msi_cookie()
 *
 * IOMMU drivers should normally call this from their domain_free callback.
 */
void iommu_put_dma_cookie(struct iommu_domain *domain)
{
    struct iommu_dma_cookie *cookie = domain->iova_cookie;
    struct iommu_dma_msi_page *msi, *tmp;

    if (!cookie) {
        return;
    }

    if (cookie->type == IOMMU_DMA_IOVA_COOKIE && cookie->iovad.granule) {
        put_iova_domain(&cookie->iovad);
    }

    list_for_each_entry_safe(msi, tmp, &cookie->msi_page_list, list)
    {
        list_del(&msi->list);
        kfree(msi);
    }
    kfree(cookie);
    domain->iova_cookie = NULL;
}
EXPORT_SYMBOL(iommu_put_dma_cookie);

/**
 * iommu_dma_get_resv_regions - Reserved region driver helper
 * @dev: Device from iommu_get_resv_regions()
 * @list: Reserved region list from iommu_get_resv_regions()
 *
 * IOMMU drivers can use this to implement their .get_resv_regions callback
 * for general non-IOMMU-specific reservations. Currently, this covers GICv3
 * ITS region reservation on ACPI based ARM platforms that may require HW MSI
 * reservation.
 */
void iommu_dma_get_resv_regions(struct device *dev, struct list_head *list)
{
    if (!is_of_node(dev_iommu_fwspec_get(dev)->iommu_fwnode)) {
        iort_iommu_msi_get_resv_regions(dev, list);
    }
}
EXPORT_SYMBOL(iommu_dma_get_resv_regions);

static int cookie_init_hw_msi_region(struct iommu_dma_cookie *cookie, phys_addr_t start, phys_addr_t end)
{
    struct iova_domain *iovad = &cookie->iovad;
    struct iommu_dma_msi_page *msi_page;
    int i, num_pages;

    start -= iova_offset(iovad, start);
    num_pages = iova_align(iovad, end - start) >> iova_shift(iovad);

    for (i = 0; i < num_pages; i++) {
        msi_page = kmalloc(sizeof(*msi_page), GFP_KERNEL);
        if (!msi_page) {
            return -ENOMEM;
        }

        msi_page->phys = start;
        msi_page->iova = start;
        INIT_LIST_HEAD(&msi_page->list);
        list_add(&msi_page->list, &cookie->msi_page_list);
        start += iovad->granule;
    }

    return 0;
}

static int iova_reserve_pci_windows(struct pci_dev *dev, struct iova_domain *iovad)
{
    struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus);
    struct resource_entry *window;
    unsigned long lo, hi;
    phys_addr_t start = 0, end;

    resource_list_for_each_entry(window, &bridge->windows)
    {
        if (resource_type(window->res) != IORESOURCE_MEM) {
            continue;
        }

        lo = iova_pfn(iovad, window->res->start - window->offset);
        hi = iova_pfn(iovad, window->res->end - window->offset);
        reserve_iova(iovad, lo, hi);
    }

    /* Get reserved DMA windows from host bridge */
    resource_list_for_each_entry(window, &bridge->dma_ranges)
    {
        end = window->res->start - window->offset;
    resv_iova:
        if (end > start) {
            lo = iova_pfn(iovad, start);
            hi = iova_pfn(iovad, end);
            reserve_iova(iovad, lo, hi);
        } else if (end < start) {
            /* dma_ranges list should be sorted */
            dev_err(&dev->dev, "Failed to reserve IOVA [%pa-%pa]\n", &start, &end);
            return -EINVAL;
        }

        start = window->res->end - window->offset + 1;
        /* If window is last entry */
        if (window->node.next == &bridge->dma_ranges && end != ~(phys_addr_t)0) {
            end = ~(phys_addr_t)0;
            goto resv_iova;
        }
    }

    return 0;
}

static int iova_reserve_iommu_regions(struct device *dev, struct iommu_domain *domain)
{
    struct iommu_dma_cookie *cookie = domain->iova_cookie;
    struct iova_domain *iovad = &cookie->iovad;
    struct iommu_resv_region *region;
    LIST_HEAD(resv_regions);
    int ret = 0;

    if (dev_is_pci(dev)) {
        ret = iova_reserve_pci_windows(to_pci_dev(dev), iovad);
        if (ret) {
            return ret;
        }
    }

    iommu_get_resv_regions(dev, &resv_regions);
    list_for_each_entry(region, &resv_regions, list)
    {
        unsigned long lo, hi;

        /* We ARE the software that manages these! */
        if (region->type == IOMMU_RESV_SW_MSI) {
            continue;
        }

        lo = iova_pfn(iovad, region->start);
        hi = iova_pfn(iovad, region->start + region->length - 1);
        reserve_iova(iovad, lo, hi);

        if (region->type == IOMMU_RESV_MSI) {
            ret = cookie_init_hw_msi_region(cookie, region->start, region->start + region->length);
        }
        if (ret) {
            break;
        }
    }
    iommu_put_resv_regions(dev, &resv_regions);

    return ret;
}

static void iommu_dma_flush_iotlb_all(struct iova_domain *iovad)
{
    struct iommu_dma_cookie *cookie;
    struct iommu_domain *domain;

    cookie = container_of(iovad, struct iommu_dma_cookie, iovad);
    domain = cookie->fq_domain;
    /*
     * The IOMMU driver supporting DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE
     * implies that ops->flush_iotlb_all must be non-NULL.
     */
    domain->ops->flush_iotlb_all(domain);
}

/**
 * iommu_dma_init_domain - Initialise a DMA mapping domain
 * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie()
 * @base: IOVA at which the mappable address space starts
 * @size: Size of IOVA space
 * @dev: Device the domain is being initialised for
 *
 * @base and @size should be exact multiples of IOMMU page granularity to
 * avoid rounding surprises. If necessary, we reserve the page at address 0
 * to ensure it is an invalid IOVA. It is safe to reinitialise a domain, but
 * any change which could make prior IOVAs invalid will fail.
 */
static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base, u64 size, struct device *dev)
{
    struct iommu_dma_cookie *cookie = domain->iova_cookie;
    unsigned long order, base_pfn;
    struct iova_domain *iovad;
    int attr;

    if (!cookie || cookie->type != IOMMU_DMA_IOVA_COOKIE) {
        return -EINVAL;
    }

    iovad = &cookie->iovad;

    /* Use the smallest supported page size for IOVA granularity */
    order = __ffs(domain->pgsize_bitmap);
    base_pfn = max_t(unsigned long, 1, base >> order);

    /* Check the domain allows at least some access to the device... */
    if (domain->geometry.force_aperture) {
        if (base > domain->geometry.aperture_end || base + size <= domain->geometry.aperture_start) {
            pr_warn("specified DMA range outside IOMMU capability\n");
            return -EFAULT;
        }
        /* ...then finally give it a kicking to make sure it fits */
        base_pfn = max_t(unsigned long, base_pfn, domain->geometry.aperture_start >> order);
    }

    /* start_pfn is always nonzero for an already-initialised domain */
    if (iovad->start_pfn) {
        if (1UL << order != iovad->granule || base_pfn != iovad->start_pfn) {
            pr_warn("Incompatible range for DMA domain\n");
            return -EFAULT;
        }

        return 0;
    }

    init_iova_domain(iovad, 1UL << order, base_pfn);

    if (!cookie->fq_domain && !iommu_domain_get_attr(domain, DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE, &attr) && attr) {
        if (init_iova_flush_queue(iovad, iommu_dma_flush_iotlb_all, NULL)) {
            pr_warn("iova flush queue initialization failed\n");
        } else {
            cookie->fq_domain = domain;
        }
    }

    if (!dev) {
        return 0;
    }

    return iova_reserve_iommu_regions(dev, domain);
}

static int iommu_dma_deferred_attach(struct device *dev, struct iommu_domain *domain)
{
    const struct iommu_ops *ops = domain->ops;

    if (!is_kdump_kernel()) {
        return 0;
    }

    if (unlikely(ops->is_attach_deferred && ops->is_attach_deferred(domain, dev))) {
        return iommu_attach_device(domain, dev);
    }

    return 0;
}

/*
 * Should be called prior to using dma-apis
 */
int iommu_dma_reserve_iova(struct device *dev, dma_addr_t base, u64 size)
{
    struct iommu_domain *domain;
    struct iommu_dma_cookie *cookie;
    struct iova_domain *iovad;
    unsigned long pfn_lo, pfn_hi;

    domain = iommu_get_domain_for_dev(dev);
    if (!domain || !domain->iova_cookie) {
        return -EINVAL;
    }

    cookie = domain->iova_cookie;
    iovad = &cookie->iovad;

    /* iova will be freed automatically by put_iova_domain() */
    pfn_lo = iova_pfn(iovad, base);
    pfn_hi = iova_pfn(iovad, base + size - 1);
    if (!reserve_iova(iovad, pfn_lo, pfn_hi)) {
        return -EINVAL;
    }

    return 0;
}
EXPORT_SYMBOL(iommu_dma_reserve_iova);

/*
 * Should be called prior to using dma-apis.
 */
int iommu_dma_enable_best_fit_algo(struct device *dev)
{
    struct iommu_domain *domain;
    struct iova_domain *iovad;

    domain = iommu_get_domain_for_dev(dev);
    if (!domain || !domain->iova_cookie) {
        return -EINVAL;
    }

    iovad = &((struct iommu_dma_cookie *)domain->iova_cookie)->iovad;
    iovad->best_fit = true;
    return 0;
}
EXPORT_SYMBOL(iommu_dma_enable_best_fit_algo);

/**
 * dma_info_to_prot - Translate DMA API directions and attributes to IOMMU API
 *                    page flags.
 * @dir: Direction of DMA transfer
 * @coherent: Is the DMA master cache-coherent?
 * @attrs: DMA attributes for the mapping
 *
 * Return: corresponding IOMMU API page protection flags
 */
static int dma_info_to_prot(enum dma_data_direction dir, bool coherent, unsigned long attrs)
{
    int prot = coherent ? IOMMU_CACHE : 0;

    if (attrs & DMA_ATTR_PRIVILEGED) {
        prot |= IOMMU_PRIV;
    }
    if (attrs & DMA_ATTR_SYS_CACHE_ONLY) {
        prot |= IOMMU_SYS_CACHE_ONLY;
    }
    if (attrs & DMA_ATTR_SYS_CACHE_ONLY_NWA) {
        prot |= IOMMU_SYS_CACHE_ONLY_NWA;
    }

    switch (dir) {
        case DMA_BIDIRECTIONAL:
            return prot | IOMMU_READ | IOMMU_WRITE;
        case DMA_TO_DEVICE:
            return prot | IOMMU_READ;
        case DMA_FROM_DEVICE:
            return prot | IOMMU_WRITE;
        default:
            return 0;
    }
}

static dma_addr_t iommu_dma_alloc_iova(struct iommu_domain *domain, size_t size, u64 dma_limit, struct device *dev)
{
    struct iommu_dma_cookie *cookie = domain->iova_cookie;
    struct iova_domain *iovad = &cookie->iovad;
    unsigned long shift, iova_len, iova = 0;

    if (cookie->type == IOMMU_DMA_MSI_COOKIE) {
        cookie->msi_iova += size;
        return cookie->msi_iova - size;
    }

    shift = iova_shift(iovad);
    iova_len = size >> shift;
    /*
     * Freeing non-power-of-two-sized allocations back into the IOVA caches
     * will come back to bite us badly, so we have to waste a bit of space
     * rounding up anything cacheable to make sure that can't happen. The
     * order of the unadjusted size will still match upon freeing.
     */
    if (iova_len < (1 << (IOVA_RANGE_CACHE_MAX_SIZE - 1))) {
        iova_len = roundup_pow_of_two(iova_len);
    }

    dma_limit = min_not_zero(dma_limit, dev->bus_dma_limit);

    if (domain->geometry.force_aperture) {
        dma_limit = min(dma_limit, (u64)domain->geometry.aperture_end);
    }

    /* Try to get PCI devices a SAC address */
    if (dma_limit > DMA_BIT_MASK(DMA_IOMMU_BIT_MASK_VALUE) && dev_is_pci(dev)) {
        iova = alloc_iova_fast(iovad, iova_len, DMA_BIT_MASK(DMA_IOMMU_BIT_MASK_VALUE) >> shift, false);
    }

    if (!iova) {
        iova = alloc_iova_fast(iovad, iova_len, dma_limit >> shift, true);
    }

    return (dma_addr_t)iova << shift;
}

static void iommu_dma_free_iova(struct iommu_dma_cookie *cookie, dma_addr_t iova, size_t size)
{
    struct iova_domain *iovad = &cookie->iovad;

    /* The MSI case is only ever cleaning up its most recent allocation */
    if (cookie->type == IOMMU_DMA_MSI_COOKIE) {
        cookie->msi_iova -= size;
    } else if (cookie->fq_domain) { /* non-strict mode */
        queue_iova(iovad, iova_pfn(iovad, iova), size >> iova_shift(iovad), 0);
    } else {
        free_iova_fast(iovad, iova_pfn(iovad, iova), size >> iova_shift(iovad));
    }
}

static void iommu_dma_unmap_ext(struct device *dev, dma_addr_t dma_addr, size_t size)
{
    struct iommu_domain *domain = iommu_get_dma_domain(dev);
    struct iommu_dma_cookie *cookie = domain->iova_cookie;
    struct iova_domain *iovad = &cookie->iovad;
    size_t iova_off = iova_offset(iovad, dma_addr);
    struct iommu_iotlb_gather iotlb_gather;
    size_t unmapped;

    dma_addr -= iova_off;
    size = iova_align(iovad, size + iova_off);
    iommu_iotlb_gather_init(&iotlb_gather);

    unmapped = iommu_unmap_fast(domain, dma_addr, size, &iotlb_gather);
    WARN_ON(unmapped != size);

    if (!cookie->fq_domain) {
        iommu_iotlb_sync(domain, &iotlb_gather);
    }
    iommu_dma_free_iova(cookie, dma_addr, size);
}

static dma_addr_t iommu_dma_map_ext(struct device *dev, phys_addr_t phys, size_t size, int prot, u64 dma_mask)
{
    struct iommu_domain *domain = iommu_get_dma_domain(dev);
    struct iommu_dma_cookie *cookie = domain->iova_cookie;
    struct iova_domain *iovad = &cookie->iovad;
    size_t iova_off = iova_offset(iovad, phys);
    dma_addr_t iova;

    if (unlikely(iommu_dma_deferred_attach(dev, domain))) {
        return DMA_MAPPING_ERROR;
    }

    size = iova_align(iovad, size + iova_off);

    iova = iommu_dma_alloc_iova(domain, size, dma_mask, dev);
    if (!iova) {
        return DMA_MAPPING_ERROR;
    }

    if (iommu_map_atomic(domain, iova, phys - iova_off, size, prot)) {
        iommu_dma_free_iova(cookie, iova, size);
        return DMA_MAPPING_ERROR;
    }
    return iova + iova_off;
}

static void iommu_dma_free_pages_ext(struct page **pages, int count)
{
    while (count--) {
        __free_page(pages[count]);
    }
    kvfree(pages);
}

static struct page **iommu_dma_alloc_pages_ext(struct device *dev, unsigned int count, unsigned long order_mask,
                                               gfp_t gfp)
{
    struct page **pages;
    unsigned int i = 0, nid = dev_to_node(dev);

    order_mask &= (2U << MAX_ORDER) - 1;
    if (!order_mask) {
        return NULL;
    }

    pages = kvzalloc(count * sizeof(*pages), GFP_KERNEL);
    if (!pages) {
        return NULL;
    }

    /* IOMMU can map any pages, so himem can also be used here */
    gfp |= __GFP_NOWARN | __GFP_HIGHMEM;

    /* It makes no sense to muck about with huge pages */
    gfp &= ~__GFP_COMP;

    while (count) {
        struct page *page = NULL;
        unsigned int order_size;

        /*
         * Higher-order allocations are a convenience rather
         * than a necessity, hence using __GFP_NORETRY until
         * falling back to minimum-order allocations.
         */
        for (order_mask &= (2U << __fls(count)) - 1; order_mask; order_mask &= ~order_size) {
            unsigned int order = __fls(order_mask);
            gfp_t alloc_flags = gfp;

            order_size = 1U << order;
            if (order_mask > (unsigned long)order_size) {
                alloc_flags |= __GFP_NORETRY;
            }
            page = alloc_pages_node(nid, alloc_flags, order);
            if (!page) {
                continue;
            }
            if (order) {
                split_page(page, order);
            }
            break;
        }
        if (!page) {
            iommu_dma_free_pages_ext(pages, i);
            return NULL;
        }
        count -= order_size;
        while (order_size--) {
            pages[i++] = page++;
        }
    }
    return pages;
}

/**
 * iommu_dma_alloc_remap - Allocate and map a buffer contiguous in IOVA space
 * @dev: Device to allocate memory for. Must be a real device
 *     attached to an iommu_dma_domain
 * @size: Size of buffer in bytes
 * @dma_handle: Out argument for allocated DMA handle
 * @gfp: Allocation flags
 * @prot: pgprot_t to use for the remapped mapping
 * @attrs: DMA attributes for this allocation
 *
 * If @size is less than PAGE_SIZE, then a full CPU page will be allocated,
 * but an IOMMU which supports smaller pages might not map the whole thing.
 *
 * Return: Mapped virtual address, or NULL on failure.
 */
static void *iommu_dma_alloc_remap(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t gfp, pgprot_t prot,
                                   unsigned long attrs)
{
    struct iommu_domain *domain = iommu_get_dma_domain(dev);
    struct iommu_dma_cookie *cookie = domain->iova_cookie;
    struct iova_domain *iovad = &cookie->iovad;
    bool coherent = dev_is_dma_coherent(dev);
    int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
    unsigned int count, min_size, alloc_sizes = domain->pgsize_bitmap;
    struct page **pages;
    struct sg_table sgt;
    dma_addr_t iova;
    void *vaddr;

    *dma_handle = DMA_MAPPING_ERROR;

    if (unlikely(iommu_dma_deferred_attach(dev, domain))) {
        return NULL;
    }

    min_size = alloc_sizes & -alloc_sizes;
    if (min_size < PAGE_SIZE) {
        min_size = PAGE_SIZE;
        alloc_sizes |= PAGE_SIZE;
    } else {
        size = ALIGN(size, min_size);
    }
    if (attrs & DMA_ATTR_ALLOC_SINGLE_PAGES) {
        alloc_sizes = min_size;
    }

    count = PAGE_ALIGN(size) >> PAGE_SHIFT;
    pages = iommu_dma_alloc_pages_ext(dev, count, alloc_sizes >> PAGE_SHIFT, gfp);
    if (!pages) {
        return NULL;
    }

    size = iova_align(iovad, size);
    iova = iommu_dma_alloc_iova(domain, size, dev->coherent_dma_mask, dev);
    if (!iova) {
        goto out_free_pages;
    }

    if (sg_alloc_table_from_pages(&sgt, pages, count, 0, size, GFP_KERNEL)) {
        goto out_free_iova;
    }

    if (!(ioprot & IOMMU_CACHE)) {
        struct scatterlist *sg;
        int i;

        for_each_sg(sgt.sgl, sg, sgt.orig_nents, i) arch_dma_prep_coherent(sg_page(sg), sg->length);
    }

    if (iommu_map_sg_atomic(domain, iova, sgt.sgl, sgt.orig_nents, ioprot) < size) {
        goto out_free_sg;
    }

    vaddr = dma_common_pages_remap(pages, size, prot, __builtin_return_address(0));
    if (!vaddr) {
        goto out_unmap;
    }

    *dma_handle = iova;
    sg_free_table(&sgt);
    return vaddr;

out_unmap:
    iommu_dma_unmap_ext(dev, iova, size);
out_free_sg:
    sg_free_table(&sgt);
out_free_iova:
    iommu_dma_free_iova(cookie, iova, size);
out_free_pages:
    iommu_dma_free_pages_ext(pages, count);
    return NULL;
}

/**
 * iommu_dma_mmap_ext - Map a buffer into provided user VMA
 * @pages: Array representing buffer from __iommu_dma_alloc()
 * @size: Size of buffer in bytes
 * @vma: VMA describing requested userspace mapping
 *
 * Maps the pages of the buffer in @pages into @vma. The caller is responsible
 * for verifying the correct size and protection of @vma beforehand.
 */
static int iommu_dma_mmap_ext(struct page **pages, size_t size, struct vm_area_struct *vma)
{
    return vm_map_pages(vma, pages, PAGE_ALIGN(size) >> PAGE_SHIFT);
}

static void iommu_dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle, size_t size,
                                          enum dma_data_direction dir)
{
    phys_addr_t phys;

    if (dev_is_dma_coherent(dev)) {
        return;
    }

    phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle);
    arch_sync_dma_for_cpu(phys, size, dir);
}

static void iommu_dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle, size_t size,
                                             enum dma_data_direction dir)
{
    phys_addr_t phys;

    if (dev_is_dma_coherent(dev)) {
        return;
    }

    phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle);
    arch_sync_dma_for_device(phys, size, dir);
}

static void iommu_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl, int nelems,
                                      enum dma_data_direction dir)
{
    struct scatterlist *sg;
    int i;

    if (dev_is_dma_coherent(dev)) {
        return;
    }

    for_each_sg(sgl, sg, nelems, i) arch_sync_dma_for_cpu(sg_phys(sg), sg->length, dir);
}

static void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl, int nelems,
                                         enum dma_data_direction dir)
{
    struct scatterlist *sg;
    int i;

    if (dev_is_dma_coherent(dev)) {
        return;
    }

    for_each_sg(sgl, sg, nelems, i) arch_sync_dma_for_device(sg_phys(sg), sg->length, dir);
}

static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, unsigned long offset, size_t size,
                                     enum dma_data_direction dir, unsigned long attrs)
{
    phys_addr_t phys = page_to_phys(page) + offset;
    bool coherent = dev_is_dma_coherent(dev);
    int prot = dma_info_to_prot(dir, coherent, attrs);
    dma_addr_t dma_handle;

    dma_handle = iommu_dma_map_ext(dev, phys, size, prot, dma_get_mask(dev));
    if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC) && dma_handle != DMA_MAPPING_ERROR) {
        arch_sync_dma_for_device(phys, size, dir);
    }
    return dma_handle;
}

static void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle, size_t size, enum dma_data_direction dir,
                                 unsigned long attrs)
{
    if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
        iommu_dma_sync_single_for_cpu(dev, dma_handle, size, dir);
    }
    iommu_dma_unmap_ext(dev, dma_handle, size);
}

/*
 * Prepare a successfully-mapped scatterlist to give back to the caller.
 *
 * At this point the segments are already laid out by iommu_dma_map_sg() to
 * avoid individually crossing any boundaries, so we merely need to check a
 * segment's start address to avoid concatenating across one.
 */
static int finalise_sg_ext(struct device *dev, struct scatterlist *sg, int nents, dma_addr_t dma_addr)
{
    struct scatterlist *s, *cur = sg;
    unsigned long seg_mask = dma_get_seg_boundary(dev);
    unsigned int cur_len = 0, max_len = dma_get_max_seg_size(dev);
    int i, count = 0;

    for_each_sg(sg, s, nents, i)
    {
        /* Restore this segment's original unaligned fields first */
        unsigned int s_iova_off = sg_dma_address(s);
        unsigned int s_length = sg_dma_len(s);
        unsigned int s_iova_len = s->length;

        s->offset += s_iova_off;
        s->length = s_length;
        sg_dma_address(s) = DMA_MAPPING_ERROR;
        sg_dma_len(s) = 0;

        /*
         * Now fill in the real DMA data. If...
         * - there is a valid output segment to append to
         * - and this segment starts on an IOVA page boundary
         * - but doesn't fall at a segment boundary
         * - and wouldn't make the resulting output segment too long
         */
        if (cur_len && !s_iova_off && (dma_addr & seg_mask) && (max_len - cur_len >= s_length)) {
            /* ...then concatenate it with the previous one */
            cur_len += s_length;
        } else {
            /* Otherwise start the next output segment */
            if (i > 0) {
                cur = sg_next(cur);
            }
            cur_len = s_length;
            count++;

            sg_dma_address(cur) = dma_addr + s_iova_off;
        }

        sg_dma_len(cur) = cur_len;
        dma_addr += s_iova_len;

        if (s_length + s_iova_off < s_iova_len) {
            cur_len = 0;
        }
    }
    return count;
}

/*
 * If mapping failed, then just restore the original list,
 * but making sure the DMA fields are invalidated.
 */
static void invalidate_sg_ext(struct scatterlist *sg, int nents)
{
    struct scatterlist *s;
    int i;

    for_each_sg(sg, s, nents, i)
    {
        if (sg_dma_address(s) != DMA_MAPPING_ERROR) {
            s->offset += sg_dma_address(s);
        }
        if (sg_dma_len(s)) {
            s->length = sg_dma_len(s);
        }
        sg_dma_address(s) = DMA_MAPPING_ERROR;
        sg_dma_len(s) = 0;
    }
}

/*
 * The DMA API client is passing in a scatterlist which could describe
 * any old buffer layout, but the IOMMU API requires everything to be
 * aligned to IOMMU pages. Hence the need for this complicated bit of
 * impedance-matching, to be able to hand off a suitably-aligned list,
 * but still preserve the original offsets and sizes for the caller.
 */
static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, int nents, enum dma_data_direction dir,
                            unsigned long attrs)
{
    struct iommu_domain *domain = iommu_get_dma_domain(dev);
    struct iommu_dma_cookie *cookie = domain->iova_cookie;
    struct iova_domain *iovad = &cookie->iovad;
    struct scatterlist *s, *prev = NULL;
    int prot = dma_info_to_prot(dir, dev_is_dma_coherent(dev), attrs);
    dma_addr_t iova;
    size_t iova_len = 0;
    unsigned long mask = dma_get_seg_boundary(dev);
    int i;

    if (unlikely(iommu_dma_deferred_attach(dev, domain))) {
        return 0;
    }

    if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
        iommu_dma_sync_sg_for_device(dev, sg, nents, dir);
    }

    /*
     * Work out how much IOVA space we need, and align the segments to
     * IOVA granules for the IOMMU driver to handle. With some clever
     * trickery we can modify the list in-place, but reversibly, by
     * stashing the unaligned parts in the as-yet-unused DMA fields.
     */
    for_each_sg(sg, s, nents, i)
    {
        size_t s_iova_off = iova_offset(iovad, s->offset);
        size_t s_length = s->length;
        size_t pad_len = (mask - iova_len + 1) & mask;

        sg_dma_address(s) = s_iova_off;
        sg_dma_len(s) = s_length;
        s->offset -= s_iova_off;
        s_length = iova_align(iovad, s_length + s_iova_off);
        s->length = s_length;

        /*
         * Due to the alignment of our single IOVA allocation, we can
         * depend on these assumptions about the segment boundary mask:
         * - If mask size >= IOVA size, then the IOVA range cannot
         *   possibly fall across a boundary, so we don't care.
         * - If mask size < IOVA size, then the IOVA range must start
         *   exactly on a boundary, therefore we can lay things out
         *   based purely on segment lengths without needing to know
         *   the actual addresses beforehand.
         * - The mask must be a power of 2, so pad_len == 0 if
         *   iova_len == 0, thus we cannot dereference prev the first
         *   time through here (i.e. before it has a meaningful value).
         */
        if (pad_len && pad_len < s_length - 1) {
            prev->length += pad_len;
            iova_len += pad_len;
        }

        iova_len += s_length;
        prev = s;
    }

    iova = iommu_dma_alloc_iova(domain, iova_len, dma_get_mask(dev), dev);
    if (!iova) {
        goto out_restore_sg;
    }

    /*
     * We'll leave any physical concatenation to the IOMMU driver's
     * implementation - it knows better than we do.
     */
    if (iommu_map_sg_atomic(domain, iova, sg, nents, prot) < iova_len) {
        goto out_free_iova;
    }

    return finalise_sg_ext(dev, sg, nents, iova);

out_free_iova:
    iommu_dma_free_iova(cookie, iova, iova_len);
out_restore_sg:
    invalidate_sg_ext(sg, nents);
    return 0;
}

static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents, enum dma_data_direction dir,
                               unsigned long attrs)
{
    dma_addr_t start, end;
    struct scatterlist *tmp;
    int i;

    if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
        iommu_dma_sync_sg_for_cpu(dev, sg, nents, dir);
    }

    /*
     * The scatterlist segments are mapped into a single
     * contiguous IOVA allocation, so this is incredibly easy.
     */
    start = sg_dma_address(sg);
    for_each_sg(sg_next(sg), tmp, nents - 1, i)
    {
        if (sg_dma_len(tmp) == 0) {
            break;
        }
        sg = tmp;
    }
    end = sg_dma_address(sg) + sg_dma_len(sg);
    iommu_dma_unmap_ext(dev, start, end - start);
}

static dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys, size_t size, enum dma_data_direction dir,
                                         unsigned long attrs)
{
    return iommu_dma_map_ext(dev, phys, size, dma_info_to_prot(dir, false, attrs) | IOMMU_MMIO, dma_get_mask(dev));
}

static void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle, size_t size, enum dma_data_direction dir,
                                     unsigned long attrs)
{
    iommu_dma_unmap_ext(dev, handle, size);
}

static void iommu_dma_free_ext(struct device *dev, size_t size, void *cpu_addr)
{
    size_t alloc_size = PAGE_ALIGN(size);
    int count = alloc_size >> PAGE_SHIFT;
    struct page *page = NULL, **pages = NULL;

    /* Non-coherent atomic allocation? Easy */
    if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && dma_free_from_pool(dev, cpu_addr, alloc_size)) {
        return;
    }

    if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
        /*
         * If it the address is remapped, then it's either non-coherent
         * or highmem CMA, or an iommu_dma_alloc_remap() construction.
         */
        pages = dma_common_find_pages(cpu_addr);
        if (!pages) {
            page = vmalloc_to_page(cpu_addr);
        }
        dma_common_free_remap(cpu_addr, alloc_size);
    } else {
        /* Lowmem means a coherent atomic or CMA allocation */
        page = virt_to_page(cpu_addr);
    }

    if (pages) {
        iommu_dma_free_pages_ext(pages, count);
    }
    if (page) {
        dma_free_contiguous(dev, page, alloc_size);
    }
}

static void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr, dma_addr_t handle, unsigned long attrs)
{
    iommu_dma_unmap_ext(dev, handle, size);
    iommu_dma_free_ext(dev, size, cpu_addr);
}

static void *iommu_dma_alloc_pages(struct device *dev, size_t size, struct page **pagep, gfp_t gfp, unsigned long attrs)
{
    bool coherent = dev_is_dma_coherent(dev);
    size_t alloc_size = PAGE_ALIGN(size);
    int node = dev_to_node(dev);
    struct page *page = NULL;
    void *cpu_addr;

    page = dma_alloc_contiguous(dev, alloc_size, gfp);
    if (!page) {
        page = alloc_pages_node(node, gfp, get_order(alloc_size));
    }
    if (!page) {
        return NULL;
    }

    if (IS_ENABLED(CONFIG_DMA_REMAP) && (!coherent || PageHighMem(page))) {
        pgprot_t prot = dma_pgprot(dev, PAGE_KERNEL, attrs);

        cpu_addr = dma_common_contiguous_remap(page, alloc_size, prot, __builtin_return_address(0));
        if (!cpu_addr) {
            goto out_free_pages;
        }

        if (!coherent) {
            arch_dma_prep_coherent(page, size);
        }
    } else {
        cpu_addr = page_address(page);
    }

    *pagep = page;
    memset(cpu_addr, 0, alloc_size);
    return cpu_addr;
out_free_pages:
    dma_free_contiguous(dev, page, alloc_size);
    return NULL;
}

static void *iommu_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
{
    bool coherent = dev_is_dma_coherent(dev);
    int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
    struct page *page = NULL;
    void *cpu_addr;

    gfp |= __GFP_ZERO;

    if (IS_ENABLED(CONFIG_DMA_REMAP) && gfpflags_allow_blocking(gfp) && !(attrs & DMA_ATTR_FORCE_CONTIGUOUS)) {
        return iommu_dma_alloc_remap(dev, size, handle, gfp, dma_pgprot(dev, PAGE_KERNEL, attrs), attrs);
    }

    if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && !gfpflags_allow_blocking(gfp) && !coherent) {
        page = dma_alloc_from_pool(dev, PAGE_ALIGN(size), &cpu_addr, gfp, NULL);
    } else {
        cpu_addr = iommu_dma_alloc_pages(dev, size, &page, gfp, attrs);
    }
    if (!cpu_addr) {
        return NULL;
    }

    *handle = iommu_dma_map_ext(dev, page_to_phys(page), size, ioprot, dev->coherent_dma_mask);
    if (*handle == DMA_MAPPING_ERROR) {
        iommu_dma_free_ext(dev, size, cpu_addr);
        return NULL;
    }

    return cpu_addr;
}

#ifdef CONFIG_DMA_REMAP
static void *iommu_dma_alloc_noncoherent(struct device *dev, size_t size, dma_addr_t *handle,
                                         enum dma_data_direction dir, gfp_t gfp)
{
    if (!gfpflags_allow_blocking(gfp)) {
        struct page *page;

        page = dma_common_alloc_pages(dev, size, handle, dir, gfp);
        if (!page) {
            return NULL;
        }
        return page_address(page);
    }

    return iommu_dma_alloc_remap(dev, size, handle, gfp | __GFP_ZERO, PAGE_KERNEL, 0);
}

static void iommu_dma_free_noncoherent(struct device *dev, size_t size, void *cpu_addr, dma_addr_t handle,
                                       enum dma_data_direction dir)
{
    iommu_dma_unmap_ext(dev, handle, size);
    iommu_dma_free_ext(dev, size, cpu_addr);
}
#else
#define iommu_dma_alloc_noncoherent NULL
#define iommu_dma_free_noncoherent NULL
#endif /* CONFIG_DMA_REMAP */

static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma, void *cpu_addr, dma_addr_t dma_addr,
                          size_t size, unsigned long attrs)
{
    unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
    unsigned long pfn, off = vma->vm_pgoff;
    int ret;

    vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);

    if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret)) {
        return ret;
    }

    if (off >= nr_pages || vma_pages(vma) > nr_pages - off) {
        return -ENXIO;
    }

    if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
        struct page **pages = dma_common_find_pages(cpu_addr);

        if (pages) {
            return iommu_dma_mmap_ext(pages, size, vma);
        }
        pfn = vmalloc_to_pfn(cpu_addr);
    } else {
        pfn = page_to_pfn(virt_to_page(cpu_addr));
    }

    return remap_pfn_range(vma, vma->vm_start, pfn + off, vma->vm_end - vma->vm_start, vma->vm_page_prot);
}

static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt, void *cpu_addr, dma_addr_t dma_addr,
                                 size_t size, unsigned long attrs)
{
    struct page *page;
    int ret;

    if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
        struct page **pages = dma_common_find_pages(cpu_addr);

        if (pages) {
            return sg_alloc_table_from_pages(sgt, pages, PAGE_ALIGN(size) >> PAGE_SHIFT, 0, size, GFP_KERNEL);
        }

        page = vmalloc_to_page(cpu_addr);
    } else {
        page = virt_to_page(cpu_addr);
    }

    ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
    if (!ret) {
        sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
    }
    return ret;
}

static unsigned long iommu_dma_get_merge_boundary(struct device *dev)
{
    struct iommu_domain *domain = iommu_get_dma_domain(dev);

    return (1UL << __ffs(domain->pgsize_bitmap)) - 1;
}

static const struct dma_map_ops iommu_dma_ops = {
    .alloc = iommu_dma_alloc,
    .free = iommu_dma_free,
    .alloc_pages = dma_common_alloc_pages,
    .free_pages = dma_common_free_pages,
    .alloc_noncoherent = iommu_dma_alloc_noncoherent,
    .free_noncoherent = iommu_dma_free_noncoherent,
    .mmap = iommu_dma_mmap,
    .get_sgtable = iommu_dma_get_sgtable,
    .map_page = iommu_dma_map_page,
    .unmap_page = iommu_dma_unmap_page,
    .map_sg = iommu_dma_map_sg,
    .unmap_sg = iommu_dma_unmap_sg,
    .sync_single_for_cpu = iommu_dma_sync_single_for_cpu,
    .sync_single_for_device = iommu_dma_sync_single_for_device,
    .sync_sg_for_cpu = iommu_dma_sync_sg_for_cpu,
    .sync_sg_for_device = iommu_dma_sync_sg_for_device,
    .map_resource = iommu_dma_map_resource,
    .unmap_resource = iommu_dma_unmap_resource,
    .get_merge_boundary = iommu_dma_get_merge_boundary,
};

/*
 * The IOMMU core code allocates the default DMA domain, which the underlying
 * IOMMU driver needs to support via the dma-iommu layer.
 */
void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size)
{
    struct iommu_domain *domain = iommu_get_domain_for_dev(dev);

    if (!domain) {
        goto out_err;
    }

    /*
     * The IOMMU core code allocates the default DMA domain, which the
     * underlying IOMMU driver needs to support via the dma-iommu layer.
     */
    if (domain->type == IOMMU_DOMAIN_DMA) {
        if (iommu_dma_init_domain(domain, dma_base, size, dev)) {
            goto out_err;
        }
        dev->dma_ops = &iommu_dma_ops;
    }

    return;
out_err:
    pr_warn("Failed to set up IOMMU for device %s; retaining platform DMA ops\n", dev_name(dev));
}

static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev, phys_addr_t msi_addr,
                                                         struct iommu_domain *domain)
{
    struct iommu_dma_cookie *cookie = domain->iova_cookie;
    struct iommu_dma_msi_page *msi_page;
    dma_addr_t iova;
    int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
    size_t size = cookie_msi_granule(cookie);

    msi_addr &= ~(phys_addr_t)(size - 1);
    list_for_each_entry(msi_page, &cookie->msi_page_list, list) if (msi_page->phys == msi_addr) return msi_page;

    msi_page = kzalloc(sizeof(*msi_page), GFP_KERNEL);
    if (!msi_page) {
        return NULL;
    }

    iova = iommu_dma_alloc_iova(domain, size, dma_get_mask(dev), dev);
    if (!iova) {
        goto out_free_page;
    }

    if (iommu_map(domain, iova, msi_addr, size, prot)) {
        goto out_free_iova;
    }

    INIT_LIST_HEAD(&msi_page->list);
    msi_page->phys = msi_addr;
    msi_page->iova = iova;
    list_add(&msi_page->list, &cookie->msi_page_list);
    return msi_page;

out_free_iova:
    iommu_dma_free_iova(cookie, iova, size);
out_free_page:
    kfree(msi_page);
    return NULL;
}

int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr)
{
    struct device *dev = msi_desc_to_dev(desc);
    struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
    struct iommu_dma_msi_page *msi_page;
    static DEFINE_MUTEX(msi_prepare_lock); /* see below */

    if (!domain || !domain->iova_cookie) {
        desc->iommu_cookie = NULL;
        return 0;
    }

    /*
     * In fact the whole prepare operation should already be serialised by
     * irq_domain_mutex further up the callchain, but that's pretty subtle
     * on its own, so consider this locking as failsafe documentation...
     */
    mutex_lock(&msi_prepare_lock);
    msi_page = iommu_dma_get_msi_page(dev, msi_addr, domain);
    mutex_unlock(&msi_prepare_lock);

    msi_desc_set_iommu_cookie(desc, msi_page);

    if (!msi_page) {
        return -ENOMEM;
    }
    return 0;
}

void iommu_dma_compose_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
{
    struct device *dev = msi_desc_to_dev(desc);
    const struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
    const struct iommu_dma_msi_page *msi_page;

    msi_page = msi_desc_get_iommu_cookie(desc);
    if (!domain || !domain->iova_cookie || WARN_ON(!msi_page)) {
        return;
    }

    msg->address_hi = upper_32_bits(msi_page->iova);
    msg->address_lo &= cookie_msi_granule(domain->iova_cookie) - 1;
    msg->address_lo += lower_32_bits(msi_page->iova);
}

static int iommu_dma_init(void)
{
    return iova_cache_get();
}
arch_initcall(iommu_dma_init);