// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Copyright 2010
 *  by Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
 *
 * This code provides a IOMMU for Xen PV guests with PCI passthrough.
 *
 * PV guests under Xen are running in an non-contiguous memory architecture.
 *
 * When PCI pass-through is utilized, this necessitates an IOMMU for
 * translating bus (DMA) to virtual and vice-versa and also providing a
 * mechanism to have contiguous pages for device drivers operations (say DMA
 * operations).
 *
 * Specifically, under Xen the Linux idea of pages is an illusion. It
 * assumes that pages start at zero and go up to the available memory. To
 * help with that, the Linux Xen MMU provides a lookup mechanism to
 * translate the page frame numbers (PFN) to machine frame numbers (MFN)
 * and vice-versa. The MFN are the "real" frame numbers. Furthermore
 * memory is not contiguous. Xen hypervisor stitches memory for guests
 * from different pools, which means there is no guarantee that PFN==MFN
 * and PFN+1==MFN+1. Lastly with Xen 4.0, pages (in debug mode) are
 * allocated in descending order (high to low), meaning the guest might
 * never get any MFN's under the 4GB mark.
 */

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#include <linux/memblock.h>
#include <linux/dma-direct.h>
#include <linux/dma-noncoherent.h>
#include <linux/export.h>
#include <xen/swiotlb-xen.h>
#include <xen/page.h>
#include <xen/xen-ops.h>
#include <xen/hvc-console.h>

#include <asm/dma-mapping.h>
#include <asm/xen/page-coherent.h>

#include <trace/events/swiotlb.h>
#define MAX_DMA_BITS 32
/*
 * Used to do a quick range check in swiotlb_tbl_unmap_single and
 * swiotlb_tbl_sync_single_*, to see if the memory was in fact allocated by this
 * API.
 */

static char *xen_io_tlb_start, *xen_io_tlb_end;
static unsigned long xen_io_tlb_nslabs;
/*
 * Quick lookup value of the bus address of the IOTLB.
 */

static u64 start_dma_addr;

/*
 * Both of these functions should avoid XEN_PFN_PHYS because phys_addr_t
 * can be 32bit when dma_addr_t is 64bit leading to a loss in
 * information if the shift is done before casting to 64bit.
 */
static inline dma_addr_t xen_phys_to_bus(phys_addr_t paddr)
{
        unsigned long bfn = pfn_to_bfn(XEN_PFN_DOWN(paddr));
        dma_addr_t dma = (dma_addr_t)bfn << XEN_PAGE_SHIFT;

        dma |= paddr & ~XEN_PAGE_MASK;

        return dma;
}

static inline phys_addr_t xen_bus_to_phys(dma_addr_t baddr)
{
        unsigned long xen_pfn = bfn_to_pfn(XEN_PFN_DOWN(baddr));
        dma_addr_t dma = (dma_addr_t)xen_pfn << XEN_PAGE_SHIFT;
        phys_addr_t paddr = dma;

        paddr |= baddr & ~XEN_PAGE_MASK;

        return paddr;
}

static inline dma_addr_t xen_virt_to_bus(void *address)
{
        return xen_phys_to_bus(virt_to_phys(address));
}

static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
{
        unsigned long next_bfn, xen_pfn = XEN_PFN_DOWN(p);
        unsigned int i, nr_pages = XEN_PFN_UP(xen_offset_in_page(p) + size);

        next_bfn = pfn_to_bfn(xen_pfn);

        for (i = 1; i < nr_pages; i++)
                if (pfn_to_bfn(++xen_pfn) != ++next_bfn)
                        return 1;

        return 0;
}

static int is_xen_swiotlb_buffer(dma_addr_t dma_addr)
{
        unsigned long bfn = XEN_PFN_DOWN(dma_addr);
        unsigned long xen_pfn = bfn_to_local_pfn(bfn);
        phys_addr_t paddr = XEN_PFN_PHYS(xen_pfn);

        /* If the address is outside our domain, it CAN
         * have the same virtual address as another address
         * in our domain. Therefore _only_ check address within our domain.
         */
        if (pfn_valid(PFN_DOWN(paddr))) {
                return paddr >= virt_to_phys(xen_io_tlb_start) &&
                       paddr < virt_to_phys(xen_io_tlb_end);
        }
        return 0;
}

static int
xen_swiotlb_fixup(void *buf, size_t size, unsigned long nslabs)
{
        int i, rc;
        int dma_bits;
        dma_addr_t dma_handle;
        phys_addr_t p = virt_to_phys(buf);

        dma_bits = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT) + PAGE_SHIFT;

        i = 0;
        do {
                int slabs = min(nslabs - i, (unsigned long)IO_TLB_SEGSIZE);

                do {
                        rc = xen_create_contiguous_region(
                                p + (i << IO_TLB_SHIFT),
                                get_order(slabs << IO_TLB_SHIFT),
                                dma_bits, &dma_handle);
                } while (rc && dma_bits++ < MAX_DMA_BITS);
                if (rc)
                        return rc;

                i += slabs;
        } while (i < nslabs);
        return 0;
}
static unsigned long xen_set_nslabs(unsigned long nr_tbl)
{
        if (!nr_tbl) {
                xen_io_tlb_nslabs = (64 * 1024 * 1024 >> IO_TLB_SHIFT);
                xen_io_tlb_nslabs = ALIGN(xen_io_tlb_nslabs, IO_TLB_SEGSIZE);
        } else
                xen_io_tlb_nslabs = nr_tbl;

        return xen_io_tlb_nslabs << IO_TLB_SHIFT;
}

enum xen_swiotlb_err {
        XEN_SWIOTLB_UNKNOWN = 0,
        XEN_SWIOTLB_ENOMEM,
        XEN_SWIOTLB_EFIXUP
};

static const char *xen_swiotlb_error(enum xen_swiotlb_err err)
{
        switch (err) {
        case XEN_SWIOTLB_ENOMEM:
                return "Cannot allocate Xen-SWIOTLB buffer\n";
        case XEN_SWIOTLB_EFIXUP:
                return "Failed to get contiguous memory for DMA from Xen!\n"\
                    "You either: don't have the permissions, do not have"\
                    " enough free memory under 4GB, or the hypervisor memory"\
                    " is too fragmented!";
        default:
                break;
        }
        return "";
}
int __ref xen_swiotlb_init(int verbose, bool early)
{
        unsigned long bytes, order;
        int rc = -ENOMEM;
        enum xen_swiotlb_err m_ret = XEN_SWIOTLB_UNKNOWN;
        unsigned int repeat = 3;

        xen_io_tlb_nslabs = swiotlb_nr_tbl();
retry:
        bytes = xen_set_nslabs(xen_io_tlb_nslabs);
        order = get_order(xen_io_tlb_nslabs << IO_TLB_SHIFT);

        /*
         * IO TLB memory already allocated. Just use it.
         */
        if (io_tlb_start != 0) {
                xen_io_tlb_start = phys_to_virt(io_tlb_start);
                goto end;
        }

        /*
         * Get IO TLB memory from any location.
         */
        if (early) {
                xen_io_tlb_start = memblock_alloc(PAGE_ALIGN(bytes),
                                                  PAGE_SIZE);
                if (!xen_io_tlb_start)
                        panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
                              __func__, PAGE_ALIGN(bytes), PAGE_SIZE);
        } else {
#define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
#define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)
                while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
                        xen_io_tlb_start = (void *)xen_get_swiotlb_free_pages(order);
                        if (xen_io_tlb_start)
                                break;
                        order--;
                }
                if (order != get_order(bytes)) {
                        pr_warn("Warning: only able to allocate %ld MB for software IO TLB\n",
                                (PAGE_SIZE << order) >> 20);
                        xen_io_tlb_nslabs = SLABS_PER_PAGE << order;
                        bytes = xen_io_tlb_nslabs << IO_TLB_SHIFT;
                }
        }
        if (!xen_io_tlb_start) {
                m_ret = XEN_SWIOTLB_ENOMEM;
                goto error;
        }
        /*
         * And replace that memory with pages under 4GB.
         */
        rc = xen_swiotlb_fixup(xen_io_tlb_start,
                               bytes,
                               xen_io_tlb_nslabs);
        if (rc) {
                if (early)
                        memblock_free(__pa(xen_io_tlb_start),
                                      PAGE_ALIGN(bytes));
                else {
                        free_pages((unsigned long)xen_io_tlb_start, order);
                        xen_io_tlb_start = NULL;
                }
                m_ret = XEN_SWIOTLB_EFIXUP;
                goto error;
        }
        start_dma_addr = xen_virt_to_bus(xen_io_tlb_start);
        if (early) {
                if (swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs,
                         verbose))
                        panic("Cannot allocate SWIOTLB buffer");
                rc = 0;
        } else
                rc = swiotlb_late_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs);

end:
        xen_io_tlb_end = xen_io_tlb_start + bytes;
        if (!rc)
                swiotlb_set_max_segment(PAGE_SIZE);

        return rc;
error:
        if (repeat--) {
                xen_io_tlb_nslabs = max(1024UL, /* Min is 2MB */
                                        (xen_io_tlb_nslabs >> 1));
                pr_info("Lowering to %luMB\n",
                        (xen_io_tlb_nslabs << IO_TLB_SHIFT) >> 20);
                goto retry;
        }
        pr_err("%s (rc:%d)\n", xen_swiotlb_error(m_ret), rc);
        if (early)
                panic("%s (rc:%d)", xen_swiotlb_error(m_ret), rc);
        else
                free_pages((unsigned long)xen_io_tlb_start, order);
        return rc;
}

static void *
xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                           dma_addr_t *dma_handle, gfp_t flags,
                           unsigned long attrs)
{
        void *ret;
        int order = get_order(size);
        u64 dma_mask = DMA_BIT_MASK(32);
        phys_addr_t phys;
        dma_addr_t dev_addr;

        /*
        * Ignore region specifiers - the kernel's ideas of
        * pseudo-phys memory layout has nothing to do with the
        * machine physical layout.  We can't allocate highmem
        * because we can't return a pointer to it.
        */
        flags &= ~(__GFP_DMA | __GFP_HIGHMEM);

        /* Convert the size to actually allocated. */
        size = 1UL << (order + XEN_PAGE_SHIFT);

        /* On ARM this function returns an ioremap'ped virtual address for
         * which virt_to_phys doesn't return the corresponding physical
         * address. In fact on ARM virt_to_phys only works for kernel direct
         * mapped RAM memory. Also see comment below.
         */
        ret = xen_alloc_coherent_pages(hwdev, size, dma_handle, flags, attrs);

        if (!ret)
                return ret;

        if (hwdev && hwdev->coherent_dma_mask)
                dma_mask = hwdev->coherent_dma_mask;

        /* At this point dma_handle is the physical address, next we are
         * going to set it to the machine address.
         * Do not use virt_to_phys(ret) because on ARM it doesn't correspond
         * to *dma_handle. */
        phys = *dma_handle;
        dev_addr = xen_phys_to_bus(phys);
        if (((dev_addr + size - 1 <= dma_mask)) &&
            !range_straddles_page_boundary(phys, size))
                *dma_handle = dev_addr;
        else {
                if (xen_create_contiguous_region(phys, order,
                                                 fls64(dma_mask), dma_handle) != 0) {
                        xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs);
                        return NULL;
                }
                SetPageXenRemapped(virt_to_page(ret));
        }
        memset(ret, 0, size);
        return ret;
}

static void
xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
                          dma_addr_t dev_addr, unsigned long attrs)
{
        int order = get_order(size);
        phys_addr_t phys;
        u64 dma_mask = DMA_BIT_MASK(32);

        if (hwdev && hwdev->coherent_dma_mask)
                dma_mask = hwdev->coherent_dma_mask;

        /* do not use virt_to_phys because on ARM it doesn't return you the
         * physical address */
        phys = xen_bus_to_phys(dev_addr);

        /* Convert the size to actually allocated. */
        size = 1UL << (order + XEN_PAGE_SHIFT);

        if (!WARN_ON((dev_addr + size - 1 > dma_mask) ||
                     range_straddles_page_boundary(phys, size)) &&
            TestClearPageXenRemapped(virt_to_page(vaddr)))
                xen_destroy_contiguous_region(phys, order);

        xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
}

/*
 * Map a single buffer of the indicated size for DMA in streaming mode.  The
 * physical address to use is returned.
 *
 * Once the device is given the dma address, the device owns this memory until
 * either xen_swiotlb_unmap_page or xen_swiotlb_dma_sync_single is performed.
 */
static dma_addr_t xen_swiotlb_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 map, phys = page_to_phys(page) + offset;
        dma_addr_t dev_addr = xen_phys_to_bus(phys);

        BUG_ON(dir == DMA_NONE);
        /*
         * If the address happens to be in the device's DMA window,
         * we can safely return the device addr and not worry about bounce
         * buffering it.
         */
        if (dma_capable(dev, dev_addr, size, true) &&
            !range_straddles_page_boundary(phys, size) &&
                !xen_arch_need_swiotlb(dev, phys, dev_addr) &&
                swiotlb_force != SWIOTLB_FORCE)
                goto done;

        /*
         * Oh well, have to allocate and map a bounce buffer.
         */
        trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force);

        map = swiotlb_tbl_map_single(dev, start_dma_addr, phys,
                                     size, size, dir, attrs);
        if (map == (phys_addr_t)DMA_MAPPING_ERROR)
                return DMA_MAPPING_ERROR;

        phys = map;
        dev_addr = xen_phys_to_bus(map);

        /*
         * Ensure that the address returned is DMA'ble
         */
        if (unlikely(!dma_capable(dev, dev_addr, size, true))) {
                swiotlb_tbl_unmap_single(dev, map, size, size, dir,
                                attrs | DMA_ATTR_SKIP_CPU_SYNC);
                return DMA_MAPPING_ERROR;
        }

done:
        if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
                xen_dma_sync_for_device(dev_addr, phys, size, dir);
        return dev_addr;
}

/*
 * Unmap a single streaming mode DMA translation.  The dma_addr and size must
 * match what was provided for in a previous xen_swiotlb_map_page call.  All
 * other usages are undefined.
 *
 * After this call, reads by the cpu to the buffer are guaranteed to see
 * whatever the device wrote there.
 */
static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
                size_t size, enum dma_data_direction dir, unsigned long attrs)
{
        phys_addr_t paddr = xen_bus_to_phys(dev_addr);

        BUG_ON(dir == DMA_NONE);

        if (!dev_is_dma_coherent(hwdev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
                xen_dma_sync_for_cpu(dev_addr, paddr, size, dir);

        /* NOTE: We use dev_addr here, not paddr! */
        if (is_xen_swiotlb_buffer(dev_addr))
                swiotlb_tbl_unmap_single(hwdev, paddr, size, size, dir, attrs);
}

static void
xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
                size_t size, enum dma_data_direction dir)
{
        phys_addr_t paddr = xen_bus_to_phys(dma_addr);

        if (!dev_is_dma_coherent(dev))
                xen_dma_sync_for_cpu(dma_addr, paddr, size, dir);

        if (is_xen_swiotlb_buffer(dma_addr))
                swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_CPU);
}

static void
xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
                size_t size, enum dma_data_direction dir)
{
        phys_addr_t paddr = xen_bus_to_phys(dma_addr);

        if (is_xen_swiotlb_buffer(dma_addr))
                swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_DEVICE);

        if (!dev_is_dma_coherent(dev))
                xen_dma_sync_for_device(dma_addr, paddr, size, dir);
}

/*
 * Unmap a set of streaming mode DMA translations.  Again, cpu read rules
 * concerning calls here are the same as for swiotlb_unmap_page() above.
 */
static void
xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
                enum dma_data_direction dir, unsigned long attrs)
{
        struct scatterlist *sg;
        int i;

        BUG_ON(dir == DMA_NONE);

        for_each_sg(sgl, sg, nelems, i)
                xen_swiotlb_unmap_page(hwdev, sg->dma_address, sg_dma_len(sg),
                                dir, attrs);

}

static int
xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
                enum dma_data_direction dir, unsigned long attrs)
{
        struct scatterlist *sg;
        int i;

        BUG_ON(dir == DMA_NONE);

        for_each_sg(sgl, sg, nelems, i) {
                sg->dma_address = xen_swiotlb_map_page(dev, sg_page(sg),
                                sg->offset, sg->length, dir, attrs);
                if (sg->dma_address == DMA_MAPPING_ERROR)
                        goto out_unmap;
                sg_dma_len(sg) = sg->length;
        }

        return nelems;
out_unmap:
        xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
        sg_dma_len(sgl) = 0;
        return 0;
}

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

        for_each_sg(sgl, sg, nelems, i) {
                xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address,
                                sg->length, dir);
        }
}

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

        for_each_sg(sgl, sg, nelems, i) {
                xen_swiotlb_sync_single_for_device(dev, sg->dma_address,
                                sg->length, dir);
        }
}

/*
 * Return whether the given device DMA address mask can be supported
 * properly.  For example, if your device can only drive the low 24-bits
 * during bus mastering, then you would pass 0x00ffffff as the mask to
 * this function.
 */
static int
xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
{
        return xen_virt_to_bus(xen_io_tlb_end - 1) <= mask;
}

const struct dma_map_ops xen_swiotlb_dma_ops = {
        .alloc = xen_swiotlb_alloc_coherent,
        .free = xen_swiotlb_free_coherent,
        .sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu,
        .sync_single_for_device = xen_swiotlb_sync_single_for_device,
        .sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
        .sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
        .map_sg = xen_swiotlb_map_sg,
        .unmap_sg = xen_swiotlb_unmap_sg,
        .map_page = xen_swiotlb_map_page,
        .unmap_page = xen_swiotlb_unmap_page,
        .dma_supported = xen_swiotlb_dma_supported,
        .mmap = dma_common_mmap,
        .get_sgtable = dma_common_get_sgtable,
};