/*
 * Handle caching attributes in page tables (PAT)
 *
 * Authors: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *          Suresh B Siddha <suresh.b.siddha@intel.com>
 *
 * Interval tree (augmented rbtree) used to store the PAT memory type
 * reservations.
 */

#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/rbtree_augmented.h>
#include <linux/sched.h>
#include <linux/gfp.h>

#include <asm/pgtable.h>
#include <asm/pat.h>

#include "pat_internal.h"

/*
 * The memtype tree keeps track of memory type for specific
 * physical memory areas. Without proper tracking, conflicting memory
 * types in different mappings can cause CPU cache corruption.
 *
 * The tree is an interval tree (augmented rbtree) with tree ordered
 * on starting address. Tree can contain multiple entries for
 * different regions which overlap. All the aliases have the same
 * cache attributes of course.
 *
 * memtype_lock protects the rbtree.
 */

static struct rb_root memtype_rbroot = RB_ROOT;

static int is_node_overlap(struct memtype *node, u64 start, u64 end)
{
        if (node->start >= end || node->end <= start)
                return 0;

        return 1;
}

static u64 get_subtree_max_end(struct rb_node *node)
{
        u64 ret = 0;
        if (node) {
                struct memtype *data = container_of(node, struct memtype, rb);
                ret = data->subtree_max_end;
        }
        return ret;
}

static u64 compute_subtree_max_end(struct memtype *data)
{
        u64 max_end = data->end, child_max_end;

        child_max_end = get_subtree_max_end(data->rb.rb_right);
        if (child_max_end > max_end)
                max_end = child_max_end;

        child_max_end = get_subtree_max_end(data->rb.rb_left);
        if (child_max_end > max_end)
                max_end = child_max_end;

        return max_end;
}

RB_DECLARE_CALLBACKS(static, memtype_rb_augment_cb, struct memtype, rb,
                     u64, subtree_max_end, compute_subtree_max_end)

/* Find the first (lowest start addr) overlapping range from rb tree */
static struct memtype *memtype_rb_lowest_match(struct rb_root *root,
                                u64 start, u64 end)
{
        struct rb_node *node = root->rb_node;
        struct memtype *last_lower = NULL;

        while (node) {
                struct memtype *data = container_of(node, struct memtype, rb);

                if (get_subtree_max_end(node->rb_left) > start) {
                        /* Lowest overlap if any must be on left side */
                        node = node->rb_left;
                } else if (is_node_overlap(data, start, end)) {
                        last_lower = data;
                        break;
                } else if (start >= data->start) {
                        /* Lowest overlap if any must be on right side */
                        node = node->rb_right;
                } else {
                        break;
                }
        }
        return last_lower; /* Returns NULL if there is no overlap */
}

static struct memtype *memtype_rb_exact_match(struct rb_root *root,
                                u64 start, u64 end)
{
        struct memtype *match;

        match = memtype_rb_lowest_match(root, start, end);
        while (match != NULL && match->start < end) {
                struct rb_node *node;

                if (match->start == start && match->end == end)
                        return match;

                node = rb_next(&match->rb);
                if (node)
                        match = container_of(node, struct memtype, rb);
                else
                        match = NULL;
        }

        return NULL; /* Returns NULL if there is no exact match */
}

static int memtype_rb_check_conflict(struct rb_root *root,
                                u64 start, u64 end,
                                enum page_cache_mode reqtype,
                                enum page_cache_mode *newtype)
{
        struct rb_node *node;
        struct memtype *match;
        enum page_cache_mode found_type = reqtype;

        match = memtype_rb_lowest_match(&memtype_rbroot, start, end);
        if (match == NULL)
                goto success;

        if (match->type != found_type && newtype == NULL)
                goto failure;

        dprintk("Overlap at 0x%Lx-0x%Lx\n", match->start, match->end);
        found_type = match->type;

        node = rb_next(&match->rb);
        while (node) {
                match = container_of(node, struct memtype, rb);

                if (match->start >= end) /* Checked all possible matches */
                        goto success;

                if (is_node_overlap(match, start, end) &&
                    match->type != found_type) {
                        goto failure;
                }

                node = rb_next(&match->rb);
        }
success:
        if (newtype)
                *newtype = found_type;

        return 0;

failure:
        pr_info("x86/PAT: %s:%d conflicting memory types %Lx-%Lx %s<->%s\n",
                current->comm, current->pid, start, end,
                cattr_name(found_type), cattr_name(match->type));
        return -EBUSY;
}

static void memtype_rb_insert(struct rb_root *root, struct memtype *newdata)
{
        struct rb_node **node = &(root->rb_node);
        struct rb_node *parent = NULL;

        while (*node) {
                struct memtype *data = container_of(*node, struct memtype, rb);

                parent = *node;
                if (data->subtree_max_end < newdata->end)
                        data->subtree_max_end = newdata->end;
                if (newdata->start <= data->start)
                        node = &((*node)->rb_left);
                else if (newdata->start > data->start)
                        node = &((*node)->rb_right);
        }

        newdata->subtree_max_end = newdata->end;
        rb_link_node(&newdata->rb, parent, node);
        rb_insert_augmented(&newdata->rb, root, &memtype_rb_augment_cb);
}

int rbt_memtype_check_insert(struct memtype *new,
                             enum page_cache_mode *ret_type)
{
        int err = 0;

        err = memtype_rb_check_conflict(&memtype_rbroot, new->start, new->end,
                                                new->type, ret_type);

        if (!err) {
                if (ret_type)
                        new->type = *ret_type;

                new->subtree_max_end = new->end;
                memtype_rb_insert(&memtype_rbroot, new);
        }
        return err;
}

struct memtype *rbt_memtype_erase(u64 start, u64 end)
{
        struct memtype *data;

        data = memtype_rb_exact_match(&memtype_rbroot, start, end);
        if (!data)
                goto out;

        rb_erase_augmented(&data->rb, &memtype_rbroot, &memtype_rb_augment_cb);
out:
        return data;
}

struct memtype *rbt_memtype_lookup(u64 addr)
{
        struct memtype *data;
        data = memtype_rb_lowest_match(&memtype_rbroot, addr, addr + PAGE_SIZE);
        return data;
}

#if defined(CONFIG_DEBUG_FS)
int rbt_memtype_copy_nth_element(struct memtype *out, loff_t pos)
{
        struct rb_node *node;
        int i = 1;

        node = rb_first(&memtype_rbroot);
        while (node && pos != i) {
                node = rb_next(node);
                i++;
        }

        if (node) { /* pos == i */
                struct memtype *this = container_of(node, struct memtype, rb);
                *out = *this;
                return 0;
        } else {
                return 1;
        }
}
#endif