Merge tag 'io_uring-5.11-2021-01-16' of git://git.kernel.dk/linux-block

[linux/fpc-iii.git] / 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/swiotlb.h>
#include <linux/scatterlist.h>
#include <linux/vmalloc.h>
#include <linux/crash_dump.h>
#include <linux/dma-direct.h>

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;
};

void iommu_dma_free_cpu_cached_iovas(unsigned int cpu,
                struct iommu_domain *domain)
{
        struct iommu_dma_cookie *cookie = domain->iova_cookie;
        struct iova_domain *iovad = &cookie->iovad;

        free_cpu_cached_iovas(cpu, iovad);
}

static void iommu_dma_entry_dtor(unsigned long data)
{
        struct page *freelist = (struct page *)data;

        while (freelist) {
                unsigned long p = (unsigned long)page_address(freelist);

                freelist = freelist->freelist;
                free_page(p);
        }
}

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 {
                        /* dma_ranges list should be sorted */
                        dev_err(&dev->dev, "Failed to reserve IOVA\n");
                        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,
                                          iommu_dma_entry_dtor))
                        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;
}

/**
 * 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;

        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(32) && dev_is_pci(dev))
                iova = alloc_iova_fast(iovad, iova_len,
                                       DMA_BIT_MASK(32) >> 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 page *freelist)
{
        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),
                                (unsigned long)freelist);
        else
                free_iova_fast(iovad, iova_pfn(iovad, iova),
                                size >> iova_shift(iovad));
}

static void __iommu_dma_unmap(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, iotlb_gather.freelist);
}

static void __iommu_dma_unmap_swiotlb(struct device *dev, dma_addr_t dma_addr,
                size_t size, 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;
        phys_addr_t phys;

        phys = iommu_iova_to_phys(domain, dma_addr);
        if (WARN_ON(!phys))
                return;

        __iommu_dma_unmap(dev, dma_addr, size);

        if (unlikely(is_swiotlb_buffer(phys)))
                swiotlb_tbl_unmap_single(dev, phys, size,
                                iova_align(iovad, size), dir, attrs);
}

static bool dev_is_untrusted(struct device *dev)
{
        return dev_is_pci(dev) && to_pci_dev(dev)->untrusted;
}

static dma_addr_t __iommu_dma_map(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, NULL);
                return DMA_MAPPING_ERROR;
        }
        return iova + iova_off;
}

static dma_addr_t __iommu_dma_map_swiotlb(struct device *dev, phys_addr_t phys,
                size_t org_size, dma_addr_t dma_mask, bool coherent,
                enum dma_data_direction dir, unsigned long attrs)
{
        int prot = dma_info_to_prot(dir, coherent, attrs);
        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 aligned_size = org_size;
        void *padding_start;
        size_t padding_size;
        dma_addr_t iova;

        /*
         * If both the physical buffer start address and size are
         * page aligned, we don't need to use a bounce page.
         */
        if (IS_ENABLED(CONFIG_SWIOTLB) && dev_is_untrusted(dev) &&
            iova_offset(iovad, phys | org_size)) {
                aligned_size = iova_align(iovad, org_size);
                phys = swiotlb_tbl_map_single(dev, phys, org_size,
                                              aligned_size, dir, attrs);

                if (phys == DMA_MAPPING_ERROR)
                        return DMA_MAPPING_ERROR;

                /* Cleanup the padding area. */
                padding_start = phys_to_virt(phys);
                padding_size = aligned_size;

                if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
                    (dir == DMA_TO_DEVICE ||
                     dir == DMA_BIDIRECTIONAL)) {
                        padding_start += org_size;
                        padding_size -= org_size;
                }

                memset(padding_start, 0, padding_size);
        }

        iova = __iommu_dma_map(dev, phys, aligned_size, prot, dma_mask);
        if ((iova == DMA_MAPPING_ERROR) && is_swiotlb_buffer(phys))
                swiotlb_tbl_unmap_single(dev, phys, org_size,
                                aligned_size, dir, attrs);

        return iova;
}

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

static struct page **__iommu_dma_alloc_pages(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 > 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(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(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(dev, iova, size);
out_free_sg:
        sg_free_table(&sgt);
out_free_iova:
        iommu_dma_free_iova(cookie, iova, size, NULL);
out_free_pages:
        __iommu_dma_free_pages(pages, count);
        return NULL;
}

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) && !dev_is_untrusted(dev))
                return;

        phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle);
        if (!dev_is_dma_coherent(dev))
                arch_sync_dma_for_cpu(phys, size, dir);

        if (is_swiotlb_buffer(phys))
                swiotlb_tbl_sync_single(dev, phys, size, dir, SYNC_FOR_CPU);
}

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) && !dev_is_untrusted(dev))
                return;

        phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle);
        if (is_swiotlb_buffer(phys))
                swiotlb_tbl_sync_single(dev, phys, size, dir, SYNC_FOR_DEVICE);

        if (!dev_is_dma_coherent(dev))
                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) && !dev_is_untrusted(dev))
                return;

        for_each_sg(sgl, sg, nelems, i) {
                if (!dev_is_dma_coherent(dev))
                        arch_sync_dma_for_cpu(sg_phys(sg), sg->length, dir);

                if (is_swiotlb_buffer(sg_phys(sg)))
                        swiotlb_tbl_sync_single(dev, sg_phys(sg), sg->length,
                                                dir, SYNC_FOR_CPU);
        }
}

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) && !dev_is_untrusted(dev))
                return;

        for_each_sg(sgl, sg, nelems, i) {
                if (is_swiotlb_buffer(sg_phys(sg)))
                        swiotlb_tbl_sync_single(dev, sg_phys(sg), sg->length,
                                                dir, SYNC_FOR_DEVICE);

                if (!dev_is_dma_coherent(dev))
                        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);
        dma_addr_t dma_handle;

        dma_handle = __iommu_dma_map_swiotlb(dev, phys, size, dma_get_mask(dev),
                        coherent, dir, attrs);
        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_swiotlb(dev, dma_handle, size, dir, attrs);
}

/*
 * 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(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(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;
        }
}

static void iommu_dma_unmap_sg_swiotlb(struct device *dev, struct scatterlist *sg,
                int nents, enum dma_data_direction dir, unsigned long attrs)
{
        struct scatterlist *s;
        int i;

        for_each_sg(sg, s, nents, i)
                __iommu_dma_unmap_swiotlb(dev, sg_dma_address(s),
                                sg_dma_len(s), dir, attrs);
}

static int iommu_dma_map_sg_swiotlb(struct device *dev, struct scatterlist *sg,
                int nents, enum dma_data_direction dir, unsigned long attrs)
{
        struct scatterlist *s;
        int i;

        for_each_sg(sg, s, nents, i) {
                sg_dma_address(s) = __iommu_dma_map_swiotlb(dev, sg_phys(s),
                                s->length, dma_get_mask(dev),
                                dev_is_dma_coherent(dev), dir, attrs);
                if (sg_dma_address(s) == DMA_MAPPING_ERROR)
                        goto out_unmap;
                sg_dma_len(s) = s->length;
        }

        return nents;

out_unmap:
        iommu_dma_unmap_sg_swiotlb(dev, sg, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
        return 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);

        if (dev_is_untrusted(dev))
                return iommu_dma_map_sg_swiotlb(dev, sg, nents, dir, attrs);

        /*
         * 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(dev, sg, nents, iova);

out_free_iova:
        iommu_dma_free_iova(cookie, iova, iova_len, NULL);
out_restore_sg:
        __invalidate_sg(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);

        if (dev_is_untrusted(dev)) {
                iommu_dma_unmap_sg_swiotlb(dev, sg, nents, dir, attrs);
                return;
        }

        /*
         * 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(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(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(dev, handle, size);
}

static void __iommu_dma_free(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(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(dev, handle, size);
        __iommu_dma_free(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(dev, page_to_phys(page), size, ioprot,
                        dev->coherent_dma_mask);
        if (*handle == DMA_MAPPING_ERROR) {
                __iommu_dma_free(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(dev, handle, size);
        __iommu_dma_free(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 vm_map_pages(vma, pages, nr_pages);
                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, NULL);
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);