xencomm.c

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 * Copyright (C) IBM Corp. 2006
 *
 * Authors: Hollis Blanchard <[email protected]>
 */

#include <linux/mm.h>
#include <linux/slab.h>
#include <asm/page.h>
#include <xen/xencomm.h>
#include <xen/interface/xen.h>
#include <asm/xen/xencomm.h>    /* for xencomm_is_phys_contiguous() */

static int xencomm_init(struct xencomm_desc *desc,
            void *buffer, unsigned long bytes)
{
    unsigned long recorded = 0;
    int i = 0;

    while ((recorded < bytes) && (i < desc->nr_addrs)) {
        unsigned long vaddr = (unsigned long)buffer + recorded;
        unsigned long paddr;
        int offset;
        int chunksz;

        offset = vaddr % PAGE_SIZE; /* handle partial pages */
        chunksz = min(PAGE_SIZE - offset, bytes - recorded);

        paddr = xencomm_vtop(vaddr);
        if (paddr == ~0UL) {
            printk(KERN_DEBUG "%s: couldn't translate vaddr %lx\n",
                   __func__, vaddr);
            return -EINVAL;
        }

        desc->address[i++] = paddr;
        recorded += chunksz;
    }

    if (recorded < bytes) {
        printk(KERN_DEBUG
               "%s: could only translate %ld of %ld bytes\n",
               __func__, recorded, bytes);
        return -ENOSPC;
    }

    /* mark remaining addresses invalid (just for safety) */
    while (i < desc->nr_addrs)
        desc->address[i++] = XENCOMM_INVALID;

    desc->magic = XENCOMM_MAGIC;

    return 0;
}

static struct xencomm_desc *xencomm_alloc(gfp_t gfp_mask,
                      void *buffer, unsigned long bytes)
{
    struct xencomm_desc *desc;
    unsigned long buffer_ulong = (unsigned long)buffer;
    unsigned long start = buffer_ulong & PAGE_MASK;
    unsigned long end = (buffer_ulong + bytes) | ~PAGE_MASK;
    unsigned long nr_addrs = (end - start + 1) >> PAGE_SHIFT;
    unsigned long size = sizeof(*desc) +
        sizeof(desc->address[0]) * nr_addrs;

    /*
     * slab allocator returns at least sizeof(void*) aligned pointer.
     * When sizeof(*desc) > sizeof(void*), struct xencomm_desc might
     * cross page boundary.
     */
    if (sizeof(*desc) > sizeof(void *)) {
        unsigned long order = get_order(size);
        desc = (struct xencomm_desc *)__get_free_pages(gfp_mask,
                                   order);
        if (desc == NULL)
            return NULL;

        desc->nr_addrs =
            ((PAGE_SIZE << order) - sizeof(struct xencomm_desc)) /
            sizeof(*desc->address);
    } else {
        desc = kmalloc(size, gfp_mask);
        if (desc == NULL)
            return NULL;

        desc->nr_addrs = nr_addrs;
    }
    return desc;
}

void xencomm_free(struct xencomm_handle *desc)
{
    if (desc && !((ulong)desc & XENCOMM_INLINE_FLAG)) {
        struct xencomm_desc *desc__ = (struct xencomm_desc *)desc;
        if (sizeof(*desc__) > sizeof(void *)) {
            unsigned long size = sizeof(*desc__) +
                sizeof(desc__->address[0]) * desc__->nr_addrs;
            unsigned long order = get_order(size);
            free_pages((unsigned long)__va(desc), order);
        } else
            kfree(__va(desc));
    }
}

static int xencomm_create(void *buffer, unsigned long bytes,
              struct xencomm_desc **ret, gfp_t gfp_mask)
{
    struct xencomm_desc *desc;
    int rc;

    pr_debug("%s: %p[%ld]\n", __func__, buffer, bytes);

    if (bytes == 0) {
        /* don't create a descriptor; Xen recognizes NULL. */
        BUG_ON(buffer != NULL);
        *ret = NULL;
        return 0;
    }

    BUG_ON(buffer == NULL); /* 'bytes' is non-zero */

    desc = xencomm_alloc(gfp_mask, buffer, bytes);
    if (!desc) {
        printk(KERN_DEBUG "%s failure\n", "xencomm_alloc");
        return -ENOMEM;
    }

    rc = xencomm_init(desc, buffer, bytes);
    if (rc) {
        printk(KERN_DEBUG "%s failure: %d\n", "xencomm_init", rc);
        xencomm_free((struct xencomm_handle *)__pa(desc));
        return rc;
    }

    *ret = desc;
    return 0;
}

static struct xencomm_handle *xencomm_create_inline(void *ptr)
{
    unsigned long paddr;

    BUG_ON(!xencomm_is_phys_contiguous((unsigned long)ptr));

    paddr = (unsigned long)xencomm_pa(ptr);
    BUG_ON(paddr & XENCOMM_INLINE_FLAG);
    return (struct xencomm_handle *)(paddr | XENCOMM_INLINE_FLAG);
}

/* "mini" routine, for stack-based communications: */
static int xencomm_create_mini(void *buffer,
    unsigned long bytes, struct xencomm_mini *xc_desc,
    struct xencomm_desc **ret)
{
    int rc = 0;
    struct xencomm_desc *desc;
    BUG_ON(((unsigned long)xc_desc) % sizeof(*xc_desc) != 0);

    desc = (void *)xc_desc;

    desc->nr_addrs = XENCOMM_MINI_ADDRS;

    rc = xencomm_init(desc, buffer, bytes);
    if (!rc)
        *ret = desc;

    return rc;
}

struct xencomm_handle *xencomm_map(void *ptr, unsigned long bytes)
{
    int rc;
    struct xencomm_desc *desc;

    if (xencomm_is_phys_contiguous((unsigned long)ptr))
        return xencomm_create_inline(ptr);

    rc = xencomm_create(ptr, bytes, &desc, GFP_KERNEL);

    if (rc || desc == NULL)
        return NULL;

    return xencomm_pa(desc);
}

struct xencomm_handle *__xencomm_map_no_alloc(void *ptr, unsigned long bytes,
            struct xencomm_mini *xc_desc)
{
    int rc;
    struct xencomm_desc *desc = NULL;

    if (xencomm_is_phys_contiguous((unsigned long)ptr))
        return xencomm_create_inline(ptr);

    rc = xencomm_create_mini(ptr, bytes, xc_desc,
                &desc);

    if (rc)
        return NULL;

    return xencomm_pa(desc);
}