// SPDX-License-Identifier: GPL-2.0-only
#include <linux/cpu.h>
#include <linux/dma-direct.h>
#include <linux/dma-map-ops.h>
#include <linux/gfp.h>
#include <linux/highmem.h>
#include <linux/export.h>
#include <linux/memblock.h>
#include <linux/of_address.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/swiotlb.h>

#include <xen/xen.h>
#include <xen/interface/grant_table.h>
#include <xen/interface/memory.h>
#include <xen/page.h>
#include <xen/xen-ops.h>
#include <xen/swiotlb-xen.h>

#include <asm/cacheflush.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/interface.h>

static gfp_t xen_swiotlb_gfp(void)
{
        phys_addr_t base;
        u64 i;

        for_each_mem_range(i, &base, NULL) {
                if (base < (phys_addr_t)0xffffffff) {
                        if (IS_ENABLED(CONFIG_ZONE_DMA32))
                                return __GFP_DMA32;
                        return __GFP_DMA;
                }
        }

        return GFP_KERNEL;
}

static bool hypercall_cflush = false;

/* buffers in highmem or foreign pages cannot cross page boundaries */
static void dma_cache_maint(struct device *dev, dma_addr_t handle,
                            size_t size, u32 op)
{
        struct gnttab_cache_flush cflush;

        cflush.offset = xen_offset_in_page(handle);
        cflush.op = op;
        handle &= XEN_PAGE_MASK;

        do {
                cflush.a.dev_bus_addr = dma_to_phys(dev, handle);

                if (size + cflush.offset > XEN_PAGE_SIZE)
                        cflush.length = XEN_PAGE_SIZE - cflush.offset;
                else
                        cflush.length = size;

                HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1);

                cflush.offset = 0;
                handle += cflush.length;
                size -= cflush.length;
        } while (size);
}

/*
 * Dom0 is mapped 1:1, and while the Linux page can span across multiple Xen
 * pages, it is not possible for it to contain a mix of local and foreign Xen
 * pages.  Calling pfn_valid on a foreign mfn will always return false, so if
 * pfn_valid returns true the pages is local and we can use the native
 * dma-direct functions, otherwise we call the Xen specific version.
 */
void xen_dma_sync_for_cpu(struct device *dev, dma_addr_t handle,
                          size_t size, enum dma_data_direction dir)
{
        if (dir != DMA_TO_DEVICE)
                dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
}

void xen_dma_sync_for_device(struct device *dev, dma_addr_t handle,
                             size_t size, enum dma_data_direction dir)
{
        if (dir == DMA_FROM_DEVICE)
                dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
        else
                dma_cache_maint(dev, handle, size, GNTTAB_CACHE_CLEAN);
}

bool xen_arch_need_swiotlb(struct device *dev,
                           phys_addr_t phys,
                           dma_addr_t dev_addr)
{
        unsigned int xen_pfn = XEN_PFN_DOWN(phys);
        unsigned int bfn = XEN_PFN_DOWN(dma_to_phys(dev, dev_addr));

        /*
         * The swiotlb buffer should be used if
         *      - Xen doesn't have the cache flush hypercall
         *      - The Linux page refers to foreign memory
         *      - The device doesn't support coherent DMA request
         *
         * The Linux page may be spanned acrros multiple Xen page, although
         * it's not possible to have a mix of local and foreign Xen page.
         * Furthermore, range_straddles_page_boundary is already checking
         * if buffer is physically contiguous in the host RAM.
         *
         * Therefore we only need to check the first Xen page to know if we
         * require a bounce buffer because the device doesn't support coherent
         * memory and we are not able to flush the cache.
         */
        return (!hypercall_cflush && (xen_pfn != bfn) &&
                !dev_is_dma_coherent(dev));
}

static int __init xen_mm_init(void)
{
        struct gnttab_cache_flush cflush;
        int rc;

        if (!xen_swiotlb_detect())
                return 0;

        /* we can work with the default swiotlb */
        rc = swiotlb_init_late(swiotlb_size_or_default(),
                               xen_swiotlb_gfp(), NULL);
        if (rc < 0)
                return rc;

        cflush.op = 0;
        cflush.a.dev_bus_addr = 0;
        cflush.offset = 0;
        cflush.length = 0;
        if (HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1) != -ENOSYS)
                hypercall_cflush = true;
        return 0;
}
arch_initcall(xen_mm_init);