/*
 * Contiguous Memory Allocator for ppc KVM hash pagetable  based on CMA
 * for DMA mapping framework
 *
 * Copyright IBM Corporation, 2013
 * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
 *
 * 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 optional) any later version of the license.
 *
 */
#define pr_fmt(fmt) "kvm_cma: " fmt

#ifdef CONFIG_CMA_DEBUG
#ifndef DEBUG
#  define DEBUG
#endif
#endif

#include <linux/memblock.h>
#include <linux/mutex.h>
#include <linux/sizes.h>
#include <linux/slab.h>

#include "book3s_hv_cma.h"

struct kvm_cma {
        unsigned long   base_pfn;
        unsigned long   count;
        unsigned long   *bitmap;
};

static DEFINE_MUTEX(kvm_cma_mutex);
static struct kvm_cma kvm_cma_area;

/**
 * kvm_cma_declare_contiguous() - reserve area for contiguous memory handling
 *                                for kvm hash pagetable
 * @size:  Size of the reserved memory.
 * @alignment:  Alignment for the contiguous memory area
 *
 * This function reserves memory for kvm cma area. It should be
 * called by arch code when early allocator (memblock or bootmem)
 * is still activate.
 */
long __init kvm_cma_declare_contiguous(phys_addr_t size, phys_addr_t alignment)
{
        long base_pfn;
        phys_addr_t addr;
        struct kvm_cma *cma = &kvm_cma_area;

        pr_debug("%s(size %lx)\n", __func__, (unsigned long)size);

        if (!size)
                return -EINVAL;
        /*
         * Sanitise input arguments.
         * We should be pageblock aligned for CMA.
         */
        alignment = max(alignment, (phys_addr_t)(PAGE_SIZE << pageblock_order));
        size = ALIGN(size, alignment);
        /*
         * Reserve memory
         * Use __memblock_alloc_base() since
         * memblock_alloc_base() panic()s.
         */
        addr = __memblock_alloc_base(size, alignment, 0);
        if (!addr) {
                base_pfn = -ENOMEM;
                goto err;
        } else
                base_pfn = PFN_DOWN(addr);

        /*
         * Each reserved area must be initialised later, when more kernel
         * subsystems (like slab allocator) are available.
         */
        cma->base_pfn = base_pfn;
        cma->count    = size >> PAGE_SHIFT;
        pr_info("CMA: reserved %ld MiB\n", (unsigned long)size / SZ_1M);
        return 0;
err:
        pr_err("CMA: failed to reserve %ld MiB\n", (unsigned long)size / SZ_1M);
        return base_pfn;
}

/**
 * kvm_alloc_cma() - allocate pages from contiguous area
 * @nr_pages: Requested number of pages.
 * @align_pages: Requested alignment in number of pages
 *
 * This function allocates memory buffer for hash pagetable.
 */
struct page *kvm_alloc_cma(unsigned long nr_pages, unsigned long align_pages)
{
        int ret;
        struct page *page = NULL;
        struct kvm_cma *cma = &kvm_cma_area;
        unsigned long chunk_count, nr_chunk;
        unsigned long mask, pfn, pageno, start = 0;


        if (!cma || !cma->count)
                return NULL;

        pr_debug("%s(cma %p, count %lu, align pages %lu)\n", __func__,
                 (void *)cma, nr_pages, align_pages);

        if (!nr_pages)
                return NULL;
        /*
         * align mask with chunk size. The bit tracks pages in chunk size
         */
        VM_BUG_ON(!is_power_of_2(align_pages));
        mask = (align_pages >> (KVM_CMA_CHUNK_ORDER - PAGE_SHIFT)) - 1;
        BUILD_BUG_ON(PAGE_SHIFT > KVM_CMA_CHUNK_ORDER);

        chunk_count = cma->count >>  (KVM_CMA_CHUNK_ORDER - PAGE_SHIFT);
        nr_chunk = nr_pages >> (KVM_CMA_CHUNK_ORDER - PAGE_SHIFT);

        mutex_lock(&kvm_cma_mutex);
        for (;;) {
                pageno = bitmap_find_next_zero_area(cma->bitmap, chunk_count,
                                                    start, nr_chunk, mask);
                if (pageno >= chunk_count)
                        break;

                pfn = cma->base_pfn + (pageno << (KVM_CMA_CHUNK_ORDER - PAGE_SHIFT));
                ret = alloc_contig_range(pfn, pfn + nr_pages, MIGRATE_CMA);
                if (ret == 0) {
                        bitmap_set(cma->bitmap, pageno, nr_chunk);
                        page = pfn_to_page(pfn);
                        memset(pfn_to_kaddr(pfn), 0, nr_pages << PAGE_SHIFT);
                        break;
                } else if (ret != -EBUSY) {
                        break;
                }
                pr_debug("%s(): memory range at %p is busy, retrying\n",
                         __func__, pfn_to_page(pfn));
                /* try again with a bit different memory target */
                start = pageno + mask + 1;
        }
        mutex_unlock(&kvm_cma_mutex);
        pr_debug("%s(): returned %p\n", __func__, page);
        return page;
}

/**
 * kvm_release_cma() - release allocated pages for hash pagetable
 * @pages: Allocated pages.
 * @nr_pages: Number of allocated pages.
 *
 * This function releases memory allocated by kvm_alloc_cma().
 * It returns false when provided pages do not belong to contiguous area and
 * true otherwise.
 */
bool kvm_release_cma(struct page *pages, unsigned long nr_pages)
{
        unsigned long pfn;
        unsigned long nr_chunk;
        struct kvm_cma *cma = &kvm_cma_area;

        if (!cma || !pages)
                return false;

        pr_debug("%s(page %p count %lu)\n", __func__, (void *)pages, nr_pages);

        pfn = page_to_pfn(pages);

        if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
                return false;

        VM_BUG_ON(pfn + nr_pages > cma->base_pfn + cma->count);
        nr_chunk = nr_pages >>  (KVM_CMA_CHUNK_ORDER - PAGE_SHIFT);

        mutex_lock(&kvm_cma_mutex);
        bitmap_clear(cma->bitmap,
                     (pfn - cma->base_pfn) >> (KVM_CMA_CHUNK_ORDER - PAGE_SHIFT),
                     nr_chunk);
        free_contig_range(pfn, nr_pages);
        mutex_unlock(&kvm_cma_mutex);

        return true;
}

static int __init kvm_cma_activate_area(unsigned long base_pfn,
                                        unsigned long count)
{
        unsigned long pfn = base_pfn;
        unsigned i = count >> pageblock_order;
        struct zone *zone;

        WARN_ON_ONCE(!pfn_valid(pfn));
        zone = page_zone(pfn_to_page(pfn));
        do {
                unsigned j;
                base_pfn = pfn;
                for (j = pageblock_nr_pages; j; --j, pfn++) {
                        WARN_ON_ONCE(!pfn_valid(pfn));
                        /*
                         * alloc_contig_range requires the pfn range
                         * specified to be in the same zone. Make this
                         * simple by forcing the entire CMA resv range
                         * to be in the same zone.
                         */
                        if (page_zone(pfn_to_page(pfn)) != zone)
                                return -EINVAL;
                }
                init_cma_reserved_pageblock(pfn_to_page(base_pfn));
        } while (--i);
        return 0;
}

static int __init kvm_cma_init_reserved_areas(void)
{
        int bitmap_size, ret;
        unsigned long chunk_count;
        struct kvm_cma *cma = &kvm_cma_area;

        pr_debug("%s()\n", __func__);
        if (!cma->count)
                return 0;
        chunk_count = cma->count >> (KVM_CMA_CHUNK_ORDER - PAGE_SHIFT);
        bitmap_size = BITS_TO_LONGS(chunk_count) * sizeof(long);
        cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
        if (!cma->bitmap)
                return -ENOMEM;

        ret = kvm_cma_activate_area(cma->base_pfn, cma->count);
        if (ret)
                goto error;
        return 0;

error:
        kfree(cma->bitmap);
        return ret;
}
core_initcall(kvm_cma_init_reserved_areas);