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/******************************************************************************

 * grant_table.c

 *

 * Granting foreign access to our memory reservation.

 *

 * Copyright (c) 2005-2006, Christopher Clark

 * Copyright (c) 2004-2005, K A Fraser

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of the GNU General Public License version 2

 * as published by the Free Software Foundation; or, when distributed

 * separately from the Linux kernel or incorporated into other

 * software packages, subject to the following license:

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this source file (the "Software"), to deal in the Software without

 * restriction, including without limitation the rights to use, copy, modify,

 * merge, publish, distribute, sublicense, and/or sell copies of the Software,

 * and to permit persons to whom the Software is furnished to do so, subject to

 * the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS

 * IN THE SOFTWARE.

 */

#include <linux/module.h>

#include <linux/sched.h>

#include <linux/mm.h>

#include <linux/vmalloc.h>

#include <linux/uaccess.h>

#include <xen/interface/xen.h>

#include <xen/page.h>

#include <xen/grant_table.h>

#include <asm/pgtable.h>

#include <asm/sync_bitops.h>

/* External tools reserve first few grant table entries. */

#define NR_RESERVED_ENTRIES 8

#define GNTTAB_LIST_END 0xffffffff

#define GREFS_PER_GRANT_FRAME (PAGE_SIZE / sizeof(struct grant_entry))

static grant_ref_t **gnttab_list;

static unsigned int nr_grant_frames;

static unsigned int boot_max_nr_grant_frames;

static int gnttab_free_count;

static grant_ref_t gnttab_free_head;

static DEFINE_SPINLOCK(gnttab_list_lock);

static struct grant_entry *shared;

static struct gnttab_free_callback *gnttab_free_callback_list;

static int gnttab_expand(unsigned int req_entries);

#define RPP (PAGE_SIZE / sizeof(grant_ref_t))

static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)

{

        return &gnttab_list[(entry) / RPP][(entry) % RPP];

}

/* This can be used as an l-value */

#define gnttab_entry(entry) (*__gnttab_entry(entry))

static int get_free_entries(unsigned count)

{

        unsigned long flags;

        int ref, rc;

        grant_ref_t head;

        spin_lock_irqsave(&gnttab_list_lock, flags);

        if ((gnttab_free_count < count) &&

            ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) {

                spin_unlock_irqrestore(&gnttab_list_lock, flags);

                return rc;

        }

        ref = head = gnttab_free_head;

        gnttab_free_count -= count;

        while (count-- > 1)

                head = gnttab_entry(head);

        gnttab_free_head = gnttab_entry(head);

        gnttab_entry(head) = GNTTAB_LIST_END;

        spin_unlock_irqrestore(&gnttab_list_lock, flags);

        return ref;

}

static void do_free_callbacks(void)

{

        struct gnttab_free_callback *callback, *next;

        callback = gnttab_free_callback_list;

        gnttab_free_callback_list = NULL;

        while (callback != NULL) {

                next = callback->next;

                if (gnttab_free_count >= callback->count) {

                        callback->next = NULL;

                        callback->fn(callback->arg);

                } else {

                        callback->next = gnttab_free_callback_list;

                        gnttab_free_callback_list = callback;

                }

                callback = next;

        }

}

static inline void check_free_callbacks(void)

{

        if (unlikely(gnttab_free_callback_list))

                do_free_callbacks();

}

static void put_free_entry(grant_ref_t ref)

{

        unsigned long flags;

        spin_lock_irqsave(&gnttab_list_lock, flags);

        gnttab_entry(ref) = gnttab_free_head;

        gnttab_free_head = ref;

        gnttab_free_count++;

        check_free_callbacks();

        spin_unlock_irqrestore(&gnttab_list_lock, flags);

}

static void update_grant_entry(grant_ref_t ref, domid_t domid,

                               unsigned long frame, unsigned flags)

{

        /*

         * Introducing a valid entry into the grant table:

         *  1. Write ent->domid.

         *  2. Write ent->frame:

         *      GTF_permit_access:   Frame to which access is permitted.

         *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new

         *                           frame, or zero if none.

         *  3. Write memory barrier (WMB).

         *  4. Write ent->flags, inc. valid type.

         */

        shared[ref].frame = frame;

        shared[ref].domid = domid;

        wmb();

        shared[ref].flags = flags;

}

/*

 * Public grant-issuing interface functions

 */

void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,

                                     unsigned long frame, int readonly)

{

        update_grant_entry(ref, domid, frame,

                           GTF_permit_access | (readonly ? GTF_readonly : 0));

}

EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref);

int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,

                                int readonly)

{

        int ref;

        ref = get_free_entries(1);

        if (unlikely(ref < 0))

                return -ENOSPC;

        gnttab_grant_foreign_access_ref(ref, domid, frame, readonly);

        return ref;

}

EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);

int gnttab_query_foreign_access(grant_ref_t ref)

{

        u16 nflags;

        nflags = shared[ref].flags;

        return (nflags & (GTF_reading|GTF_writing));

}

EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);

int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)

{

        u16 flags, nflags;

        nflags = shared[ref].flags;

        do {

                flags = nflags;

                if (flags & (GTF_reading|GTF_writing)) {

                        printk(KERN_ALERT "WARNING: g.e. still in use!\n");

                        return 0;

                }

        } while ((nflags = sync_cmpxchg(&shared[ref].flags, flags, 0)) != flags);

        return 1;

}

EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);

void gnttab_end_foreign_access(grant_ref_t ref, int readonly,

                               unsigned long page)

{

        if (gnttab_end_foreign_access_ref(ref, readonly)) {

                put_free_entry(ref);

                if (page != 0)

                        free_page(page);

        } else {

                /* XXX This needs to be fixed so that the ref and page are

                   placed on a list to be freed up later. */

                printk(KERN_WARNING

                       "WARNING: leaking g.e. and page still in use!\n");

        }

}

EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);

int gnttab_grant_foreign_transfer(domid_t domid, unsigned long pfn)

{

        int ref;

        ref = get_free_entries(1);

        if (unlikely(ref < 0))

                return -ENOSPC;

        gnttab_grant_foreign_transfer_ref(ref, domid, pfn);

        return ref;

}

EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer);

void gnttab_grant_foreign_transfer_ref(grant_ref_t ref, domid_t domid,

                                       unsigned long pfn)

{

        update_grant_entry(ref, domid, pfn, GTF_accept_transfer);

}

EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer_ref);

unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref)

{

        unsigned long frame;

        u16           flags;

        /*

         * If a transfer is not even yet started, try to reclaim the grant

         * reference and return failure (== 0).

         */

        while (!((flags = shared[ref].flags) & GTF_transfer_committed)) {

                if (sync_cmpxchg(&shared[ref].flags, flags, 0) == flags)

                        return 0;

                cpu_relax();

        }

        /* If a transfer is in progress then wait until it is completed. */

        while (!(flags & GTF_transfer_completed)) {

                flags = shared[ref].flags;

                cpu_relax();

        }

        rmb();  /* Read the frame number /after/ reading completion status. */

        frame = shared[ref].frame;

        BUG_ON(frame == 0);

        return frame;

}

EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer_ref);

unsigned long gnttab_end_foreign_transfer(grant_ref_t ref)

{

        unsigned long frame = gnttab_end_foreign_transfer_ref(ref);

        put_free_entry(ref);

        return frame;

}

EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer);

void gnttab_free_grant_reference(grant_ref_t ref)

{

        put_free_entry(ref);

}

EXPORT_SYMBOL_GPL(gnttab_free_grant_reference);

void gnttab_free_grant_references(grant_ref_t head)

{

        grant_ref_t ref;

        unsigned long flags;

        int count = 1;

        if (head == GNTTAB_LIST_END)

                return;

        spin_lock_irqsave(&gnttab_list_lock, flags);

        ref = head;

        while (gnttab_entry(ref) != GNTTAB_LIST_END) {

                ref = gnttab_entry(ref);

                count++;

        }

        gnttab_entry(ref) = gnttab_free_head;

        gnttab_free_head = head;

        gnttab_free_count += count;

        check_free_callbacks();

        spin_unlock_irqrestore(&gnttab_list_lock, flags);

}

EXPORT_SYMBOL_GPL(gnttab_free_grant_references);

int gnttab_alloc_grant_references(u16 count, grant_ref_t *head)

{

        int h = get_free_entries(count);

        if (h < 0)

                return -ENOSPC;

        *head = h;

        return 0;

}

EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references);

int gnttab_empty_grant_references(const grant_ref_t *private_head)

{

        return (*private_head == GNTTAB_LIST_END);

}

EXPORT_SYMBOL_GPL(gnttab_empty_grant_references);

int gnttab_claim_grant_reference(grant_ref_t *private_head)

{

        grant_ref_t g = *private_head;

        if (unlikely(g == GNTTAB_LIST_END))

                return -ENOSPC;

        *private_head = gnttab_entry(g);

        return g;

}

EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference);

void gnttab_release_grant_reference(grant_ref_t *private_head,

                                    grant_ref_t release)

{

        gnttab_entry(release) = *private_head;

        *private_head = release;

}

EXPORT_SYMBOL_GPL(gnttab_release_grant_reference);

void gnttab_request_free_callback(struct gnttab_free_callback *callback,

                                  void (*fn)(void *), void *arg, u16 count)

{

        unsigned long flags;

        spin_lock_irqsave(&gnttab_list_lock, flags);

        if (callback->next)

                goto out;

        callback->fn = fn;

        callback->arg = arg;

        callback->count = count;

        callback->next = gnttab_free_callback_list;

        gnttab_free_callback_list = callback;

        check_free_callbacks();

out:

        spin_unlock_irqrestore(&gnttab_list_lock, flags);

}

EXPORT_SYMBOL_GPL(gnttab_request_free_callback);

void gnttab_cancel_free_callback(struct gnttab_free_callback *callback)

{

        struct gnttab_free_callback **pcb;

        unsigned long flags;

        spin_lock_irqsave(&gnttab_list_lock, flags);

        for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) {

                if (*pcb == callback) {

                        *pcb = callback->next;

                        break;

                }

        }

        spin_unlock_irqrestore(&gnttab_list_lock, flags);

}

EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback);

static int grow_gnttab_list(unsigned int more_frames)

{

        unsigned int new_nr_grant_frames, extra_entries, i;

        new_nr_grant_frames = nr_grant_frames + more_frames;

        extra_entries       = more_frames * GREFS_PER_GRANT_FRAME;

        for (i = nr_grant_frames; i < new_nr_grant_frames; i++) {

                gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);

                if (!gnttab_list[i])

                        goto grow_nomem;

        }

        for (i = GREFS_PER_GRANT_FRAME * nr_grant_frames;

             i < GREFS_PER_GRANT_FRAME * new_nr_grant_frames - 1; i++)

                gnttab_entry(i) = i + 1;

        gnttab_entry(i) = gnttab_free_head;

        gnttab_free_head = GREFS_PER_GRANT_FRAME * nr_grant_frames;

        gnttab_free_count += extra_entries;

        nr_grant_frames = new_nr_grant_frames;

        check_free_callbacks();

        return 0;

grow_nomem:

        for ( ; i >= nr_grant_frames; i--)

                free_page((unsigned long) gnttab_list[i]);

        return -ENOMEM;

}

static unsigned int __max_nr_grant_frames(void)

{

        struct gnttab_query_size query;

        int rc;

        query.dom = DOMID_SELF;

        rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1);

        if ((rc < 0) || (query.status != GNTST_okay))

                return 4; /* Legacy max supported number of frames */

        return query.max_nr_frames;

}

static inline unsigned int max_nr_grant_frames(void)

{

        unsigned int xen_max = __max_nr_grant_frames();

        if (xen_max > boot_max_nr_grant_frames)

                return boot_max_nr_grant_frames;

        return xen_max;

}

static int map_pte_fn(pte_t *pte, struct page *pmd_page,

                      unsigned long addr, void *data)

{

        unsigned long **frames = (unsigned long **)data;

        set_pte_at(&init_mm, addr, pte, mfn_pte((*frames)[0], PAGE_KERNEL));

        (*frames)++;

        return 0;

}

static int unmap_pte_fn(pte_t *pte, struct page *pmd_page,

                        unsigned long addr, void *data)

{

        set_pte_at(&init_mm, addr, pte, __pte(0));

        return 0;

}

static int gnttab_map(unsigned int start_idx, unsigned int end_idx)

{

        struct gnttab_setup_table setup;

        unsigned long *frames;

        unsigned int nr_gframes = end_idx + 1;

        int rc;

        frames = kmalloc(nr_gframes * sizeof(unsigned long), GFP_ATOMIC);

        if (!frames)

                return -ENOMEM;

        setup.dom        = DOMID_SELF;

        setup.nr_frames  = nr_gframes;

        setup.frame_list = frames;

        rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);

        if (rc == -ENOSYS) {

                kfree(frames);

                return -ENOSYS;

        }

        BUG_ON(rc || setup.status);

        if (shared == NULL) {

                struct vm_struct *area;

                area = alloc_vm_area(PAGE_SIZE * max_nr_grant_frames());

                BUG_ON(area == NULL);

                shared = area->addr;

        }

        rc = apply_to_page_range(&init_mm, (unsigned long)shared,

                                 PAGE_SIZE * nr_gframes,

                                 map_pte_fn, &frames);

        BUG_ON(rc);

        frames -= nr_gframes; /* adjust after map_pte_fn() */

        kfree(frames);

        return 0;

}

static int gnttab_resume(void)

{

        if (max_nr_grant_frames() < nr_grant_frames)

                return -ENOSYS;

        return gnttab_map(0, nr_grant_frames - 1);

}

static int gnttab_suspend(void)

{

        apply_to_page_range(&init_mm, (unsigned long)shared,

                            PAGE_SIZE * nr_grant_frames,

                            unmap_pte_fn, NULL);

        return 0;

}

static int gnttab_expand(unsigned int req_entries)

{

        int rc;

        unsigned int cur, extra;

        cur = nr_grant_frames;

        extra = ((req_entries + (GREFS_PER_GRANT_FRAME-1)) /

                 GREFS_PER_GRANT_FRAME);

        if (cur + extra > max_nr_grant_frames())

                return -ENOSPC;

        rc = gnttab_map(cur, cur + extra - 1);

        if (rc == 0)

                rc = grow_gnttab_list(extra);

        return rc;

}

static int __devinit gnttab_init(void)

{

        int i;

        unsigned int max_nr_glist_frames;

        unsigned int nr_init_grefs;

        if (!is_running_on_xen())

                return -ENODEV;

        nr_grant_frames = 1;

        boot_max_nr_grant_frames = __max_nr_grant_frames();

        /* Determine the maximum number of frames required for the

         * grant reference free list on the current hypervisor.

         */

        max_nr_glist_frames = (boot_max_nr_grant_frames *

                               GREFS_PER_GRANT_FRAME /

                               (PAGE_SIZE / sizeof(grant_ref_t)));

        gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),

                              GFP_KERNEL);

        if (gnttab_list == NULL)

                return -ENOMEM;

        for (i = 0; i < nr_grant_frames; i++) {

                gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);

                if (gnttab_list[i] == NULL)

                        goto ini_nomem;

        }

        if (gnttab_resume() < 0)

                return -ENODEV;

        nr_init_grefs = nr_grant_frames * GREFS_PER_GRANT_FRAME;

        for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++)

                gnttab_entry(i) = i + 1;

        gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END;

        gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES;

        gnttab_free_head  = NR_RESERVED_ENTRIES;

        printk("Grant table initialized\n");

        return 0;

 ini_nomem:

        for (i--; i >= 0; i--)

                free_page((unsigned long)gnttab_list[i]);

        kfree(gnttab_list);

        return -ENOMEM;

}

core_initcall(gnttab_init);