swiotlb-xen.c

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/*
 *  Copyright 2010
 *  by Konrad Rzeszutek Wilk <[email protected]>
 *
 * This code provides a IOMMU for Xen PV guests with PCI passthrough.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License v2.0 as published by
 * the Free Software Foundation
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * 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.
 *
 */

#include <linux/bootmem.h>
#include <linux/dma-mapping.h>
#include <linux/export.h>
#include <xen/swiotlb-xen.h>
#include <xen/page.h>
#include <xen/xen-ops.h>
#include <xen/hvc-console.h>
/*
 * 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;

static dma_addr_t xen_phys_to_bus(phys_addr_t paddr)
{
    return phys_to_machine(XPADDR(paddr)).maddr;
}

static phys_addr_t xen_bus_to_phys(dma_addr_t baddr)
{
    return machine_to_phys(XMADDR(baddr)).paddr;
}

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

static int check_pages_physically_contiguous(unsigned long pfn,
                         unsigned int offset,
                         size_t length)
{
    unsigned long next_mfn;
    int i;
    int nr_pages;

    next_mfn = pfn_to_mfn(pfn);
    nr_pages = (offset + length + PAGE_SIZE-1) >> PAGE_SHIFT;

    for (i = 1; i < nr_pages; i++) {
        if (pfn_to_mfn(++pfn) != ++next_mfn)
            return 0;
    }
    return 1;
}

static int range_straddles_page_boundary(phys_addr_t p, size_t size)
{
    unsigned long pfn = PFN_DOWN(p);
    unsigned int offset = p & ~PAGE_MASK;

    if (offset + size <= PAGE_SIZE)
        return 0;
    if (check_pages_physically_contiguous(pfn, offset, size))
        return 0;
    return 1;
}

static int is_xen_swiotlb_buffer(dma_addr_t dma_addr)
{
    unsigned long mfn = PFN_DOWN(dma_addr);
    unsigned long pfn = mfn_to_local_pfn(mfn);
    phys_addr_t paddr;

    /* 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)) {
        paddr = PFN_PHYS(pfn);
        return paddr >= virt_to_phys(xen_io_tlb_start) &&
               paddr < virt_to_phys(xen_io_tlb_end);
    }
    return 0;
}

static int max_dma_bits = 32;

static int
xen_swiotlb_fixup(void *buf, size_t size, unsigned long nslabs)
{
    int i, rc;
    int dma_bits;

    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(
                (unsigned long)buf + (i << IO_TLB_SHIFT),
                get_order(slabs << IO_TLB_SHIFT),
                dma_bits);
        } 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);
    /*
     * Get IO TLB memory from any location.
     */
    if (early)
        xen_io_tlb_start = alloc_bootmem_pages(PAGE_ALIGN(bytes));
    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 *)__get_free_pages(__GFP_NOWARN, 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;
    }
    xen_io_tlb_end = xen_io_tlb_start + bytes;
    /*
     * 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)
            free_bootmem(__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) {
        swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, verbose);
        rc = 0;
    } else
        rc = swiotlb_late_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs);
    return rc;
error:
    if (repeat--) {
        xen_io_tlb_nslabs = max(1024UL, /* Min is 2MB */
                    (xen_io_tlb_nslabs >> 1));
        printk(KERN_INFO "Xen-SWIOTLB: Lowering to %luMB\n",
              (xen_io_tlb_nslabs << IO_TLB_SHIFT) >> 20);
        goto retry;
    }
    pr_err("%s (rc:%d)", 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;
}
void *
xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
               dma_addr_t *dma_handle, gfp_t flags,
               struct dma_attrs *attrs)
{
    void *ret;
    int order = get_order(size);
    u64 dma_mask = DMA_BIT_MASK(32);
    unsigned long vstart;
    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);

    if (dma_alloc_from_coherent(hwdev, size, dma_handle, &ret))
        return ret;

    vstart = __get_free_pages(flags, order);
    ret = (void *)vstart;

    if (!ret)
        return ret;

    if (hwdev && hwdev->coherent_dma_mask)
        dma_mask = dma_alloc_coherent_mask(hwdev, flags);

    phys = virt_to_phys(ret);
    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(vstart, order,
                         fls64(dma_mask)) != 0) {
            free_pages(vstart, order);
            return NULL;
        }
        *dma_handle = virt_to_machine(ret).maddr;
    }
    memset(ret, 0, size);
    return ret;
}
EXPORT_SYMBOL_GPL(xen_swiotlb_alloc_coherent);

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

    if (dma_release_from_coherent(hwdev, order, vaddr))
        return;

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

    phys = virt_to_phys(vaddr);

    if (((dev_addr + size - 1 > dma_mask)) ||
        range_straddles_page_boundary(phys, size))
        xen_destroy_contiguous_region((unsigned long)vaddr, order);

    free_pages((unsigned long)vaddr, order);
}
EXPORT_SYMBOL_GPL(xen_swiotlb_free_coherent);


/*
 * 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.
 */
dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
                unsigned long offset, size_t size,
                enum dma_data_direction dir,
                struct dma_attrs *attrs)
{
    phys_addr_t phys = page_to_phys(page) + offset;
    dma_addr_t dev_addr = xen_phys_to_bus(phys);
    void *map;

    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) &&
        !range_straddles_page_boundary(phys, size) && !swiotlb_force)
        return dev_addr;

    /*
     * Oh well, have to allocate and map a bounce buffer.
     */
    map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, size, dir);
    if (!map)
        return DMA_ERROR_CODE;

    dev_addr = xen_virt_to_bus(map);

    /*
     * Ensure that the address returned is DMA'ble
     */
    if (!dma_capable(dev, dev_addr, size)) {
        swiotlb_tbl_unmap_single(dev, map, size, dir);
        dev_addr = 0;
    }
    return dev_addr;
}
EXPORT_SYMBOL_GPL(xen_swiotlb_map_page);

/*
 * 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_unmap_single(struct device *hwdev, dma_addr_t dev_addr,
                 size_t size, enum dma_data_direction dir)
{
    phys_addr_t paddr = xen_bus_to_phys(dev_addr);

    BUG_ON(dir == DMA_NONE);

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

    if (dir != DMA_FROM_DEVICE)
        return;

    /*
     * phys_to_virt doesn't work with hihgmem page but we could
     * call dma_mark_clean() with hihgmem page here. However, we
     * are fine since dma_mark_clean() is null on POWERPC. We can
     * make dma_mark_clean() take a physical address if necessary.
     */
    dma_mark_clean(phys_to_virt(paddr), size);
}

void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
                size_t size, enum dma_data_direction dir,
                struct dma_attrs *attrs)
{
    xen_unmap_single(hwdev, dev_addr, size, dir);
}
EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_page);

/*
 * Make physical memory consistent for a single streaming mode DMA translation
 * after a transfer.
 *
 * If you perform a xen_swiotlb_map_page() but wish to interrogate the buffer
 * using the cpu, yet do not wish to teardown the dma mapping, you must
 * call this function before doing so.  At the next point you give the dma
 * address back to the card, you must first perform a
 * xen_swiotlb_dma_sync_for_device, and then the device again owns the buffer
 */
static void
xen_swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
            size_t size, enum dma_data_direction dir,
            enum dma_sync_target target)
{
    phys_addr_t paddr = xen_bus_to_phys(dev_addr);

    BUG_ON(dir == DMA_NONE);

    /* NOTE: We use dev_addr here, not paddr! */
    if (is_xen_swiotlb_buffer(dev_addr)) {
        swiotlb_tbl_sync_single(hwdev, phys_to_virt(paddr), size, dir,
                       target);
        return;
    }

    if (dir != DMA_FROM_DEVICE)
        return;

    dma_mark_clean(phys_to_virt(paddr), size);
}

void
xen_swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
                size_t size, enum dma_data_direction dir)
{
    xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_CPU);
}
EXPORT_SYMBOL_GPL(xen_swiotlb_sync_single_for_cpu);

void
xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
                   size_t size, enum dma_data_direction dir)
{
    xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_DEVICE);
}
EXPORT_SYMBOL_GPL(xen_swiotlb_sync_single_for_device);

/*
 * Map a set of buffers described by scatterlist in streaming mode for DMA.
 * This is the scatter-gather version of the above xen_swiotlb_map_page
 * interface.  Here the scatter gather list elements are each tagged with the
 * appropriate dma address and length.  They are obtained via
 * sg_dma_{address,length}(SG).
 *
 * NOTE: An implementation may be able to use a smaller number of
 *       DMA address/length pairs than there are SG table elements.
 *       (for example via virtual mapping capabilities)
 *       The routine returns the number of addr/length pairs actually
 *       used, at most nents.
 *
 * Device ownership issues as mentioned above for xen_swiotlb_map_page are the
 * same here.
 */
int
xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
             int nelems, enum dma_data_direction dir,
             struct dma_attrs *attrs)
{
    struct scatterlist *sg;
    int i;

    BUG_ON(dir == DMA_NONE);

    for_each_sg(sgl, sg, nelems, i) {
        phys_addr_t paddr = sg_phys(sg);
        dma_addr_t dev_addr = xen_phys_to_bus(paddr);

        if (swiotlb_force ||
            !dma_capable(hwdev, dev_addr, sg->length) ||
            range_straddles_page_boundary(paddr, sg->length)) {
            void *map = swiotlb_tbl_map_single(hwdev,
                               start_dma_addr,
                               sg_phys(sg),
                               sg->length, dir);
            if (!map) {
                /* Don't panic here, we expect map_sg users
                   to do proper error handling. */
                xen_swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
                               attrs);
                sgl[0].dma_length = 0;
                return DMA_ERROR_CODE;
            }
            sg->dma_address = xen_virt_to_bus(map);
        } else
            sg->dma_address = dev_addr;
        sg->dma_length = sg->length;
    }
    return nelems;
}
EXPORT_SYMBOL_GPL(xen_swiotlb_map_sg_attrs);

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

    BUG_ON(dir == DMA_NONE);

    for_each_sg(sgl, sg, nelems, i)
        xen_unmap_single(hwdev, sg->dma_address, sg->dma_length, dir);

}
EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_sg_attrs);

/*
 * Make physical memory consistent for a set of streaming mode DMA translations
 * after a transfer.
 *
 * The same as swiotlb_sync_single_* but for a scatter-gather list, same rules
 * and usage.
 */
static void
xen_swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sgl,
            int nelems, enum dma_data_direction dir,
            enum dma_sync_target target)
{
    struct scatterlist *sg;
    int i;

    for_each_sg(sgl, sg, nelems, i)
        xen_swiotlb_sync_single(hwdev, sg->dma_address,
                    sg->dma_length, dir, target);
}

void
xen_swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
                int nelems, enum dma_data_direction dir)
{
    xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_CPU);
}
EXPORT_SYMBOL_GPL(xen_swiotlb_sync_sg_for_cpu);

void
xen_swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
                   int nelems, enum dma_data_direction dir)
{
    xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_DEVICE);
}
EXPORT_SYMBOL_GPL(xen_swiotlb_sync_sg_for_device);

int
xen_swiotlb_dma_mapping_error(struct device *hwdev, dma_addr_t dma_addr)
{
    return !dma_addr;
}
EXPORT_SYMBOL_GPL(xen_swiotlb_dma_mapping_error);

/*
 * 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.
 */
int
xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
{
    return xen_virt_to_bus(xen_io_tlb_end - 1) <= mask;
}
EXPORT_SYMBOL_GPL(xen_swiotlb_dma_supported);