/*
 * 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);