/*	$NetBSD: scatterlist.c,v 1.2 2021/12/18 23:45:31 riastradh Exp $	*/

/*
 * Copyright © 2016 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (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 (including the next
 * paragraph) 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 <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: scatterlist.c,v 1.2 2021/12/18 23:45:31 riastradh Exp $");

#include <linux/prime_numbers.h>
#include <linux/random.h>

#include "i915_selftest.h"
#include "i915_utils.h"

#define PFN_BIAS (1 << 10)

struct pfn_table {
	struct sg_table st;
	unsigned long start, end;
};

typedef unsigned int (*npages_fn_t)(unsigned long n,
				    unsigned long count,
				    struct rnd_state *rnd);

static noinline int expect_pfn_sg(struct pfn_table *pt,
				  npages_fn_t npages_fn,
				  struct rnd_state *rnd,
				  const char *who,
				  unsigned long timeout)
{
	struct scatterlist *sg;
	unsigned long pfn, n;

	pfn = pt->start;
	for_each_sg(pt->st.sgl, sg, pt->st.nents, n) {
		struct page *page = sg_page(sg);
		unsigned int npages = npages_fn(n, pt->st.nents, rnd);

		if (page_to_pfn(page) != pfn) {
			pr_err("%s: %s left pages out of order, expected pfn %lu, found pfn %lu (using for_each_sg)\n",
			       __func__, who, pfn, page_to_pfn(page));
			return -EINVAL;
		}

		if (sg->length != npages * PAGE_SIZE) {
			pr_err("%s: %s copied wrong sg length, expected size %lu, found %u (using for_each_sg)\n",
			       __func__, who, npages * PAGE_SIZE, sg->length);
			return -EINVAL;
		}

		if (igt_timeout(timeout, "%s timed out\n", who))
			return -EINTR;

		pfn += npages;
	}
	if (pfn != pt->end) {
		pr_err("%s: %s finished on wrong pfn, expected %lu, found %lu\n",
		       __func__, who, pt->end, pfn);
		return -EINVAL;
	}

	return 0;
}

static noinline int expect_pfn_sg_page_iter(struct pfn_table *pt,
					    const char *who,
					    unsigned long timeout)
{
	struct sg_page_iter sgiter;
	unsigned long pfn;

	pfn = pt->start;
	for_each_sg_page(pt->st.sgl, &sgiter, pt->st.nents, 0) {
		struct page *page = sg_page_iter_page(&sgiter);

		if (page != pfn_to_page(pfn)) {
			pr_err("%s: %s left pages out of order, expected pfn %lu, found pfn %lu (using for_each_sg_page)\n",
			       __func__, who, pfn, page_to_pfn(page));
			return -EINVAL;
		}

		if (igt_timeout(timeout, "%s timed out\n", who))
			return -EINTR;

		pfn++;
	}
	if (pfn != pt->end) {
		pr_err("%s: %s finished on wrong pfn, expected %lu, found %lu\n",
		       __func__, who, pt->end, pfn);
		return -EINVAL;
	}

	return 0;
}

static noinline int expect_pfn_sgtiter(struct pfn_table *pt,
				       const char *who,
				       unsigned long timeout)
{
	struct sgt_iter sgt;
	struct page *page;
	unsigned long pfn;

	pfn = pt->start;
	for_each_sgt_page(page, sgt, &pt->st) {
		if (page != pfn_to_page(pfn)) {
			pr_err("%s: %s left pages out of order, expected pfn %lu, found pfn %lu (using for_each_sgt_page)\n",
			       __func__, who, pfn, page_to_pfn(page));
			return -EINVAL;
		}

		if (igt_timeout(timeout, "%s timed out\n", who))
			return -EINTR;

		pfn++;
	}
	if (pfn != pt->end) {
		pr_err("%s: %s finished on wrong pfn, expected %lu, found %lu\n",
		       __func__, who, pt->end, pfn);
		return -EINVAL;
	}

	return 0;
}

static int expect_pfn_sgtable(struct pfn_table *pt,
			      npages_fn_t npages_fn,
			      struct rnd_state *rnd,
			      const char *who,
			      unsigned long timeout)
{
	int err;

	err = expect_pfn_sg(pt, npages_fn, rnd, who, timeout);
	if (err)
		return err;

	err = expect_pfn_sg_page_iter(pt, who, timeout);
	if (err)
		return err;

	err = expect_pfn_sgtiter(pt, who, timeout);
	if (err)
		return err;

	return 0;
}

static unsigned int one(unsigned long n,
			unsigned long count,
			struct rnd_state *rnd)
{
	return 1;
}

static unsigned int grow(unsigned long n,
			 unsigned long count,
			 struct rnd_state *rnd)
{
	return n + 1;
}

static unsigned int shrink(unsigned long n,
			   unsigned long count,
			   struct rnd_state *rnd)
{
	return count - n;
}

static unsigned int random(unsigned long n,
			   unsigned long count,
			   struct rnd_state *rnd)
{
	return 1 + (prandom_u32_state(rnd) % 1024);
}

static unsigned int random_page_size_pages(unsigned long n,
					   unsigned long count,
					   struct rnd_state *rnd)
{
	/* 4K, 64K, 2M */
	static unsigned int page_count[] = {
		BIT(12) >> PAGE_SHIFT,
		BIT(16) >> PAGE_SHIFT,
		BIT(21) >> PAGE_SHIFT,
	};

	return page_count[(prandom_u32_state(rnd) % 3)];
}

static inline bool page_contiguous(struct page *first,
				   struct page *last,
				   unsigned long npages)
{
	return first + npages == last;
}

static int alloc_table(struct pfn_table *pt,
		       unsigned long count, unsigned long max,
		       npages_fn_t npages_fn,
		       struct rnd_state *rnd,
		       int alloc_error)
{
	struct scatterlist *sg;
	unsigned long n, pfn;

	if (sg_alloc_table(&pt->st, max,
			   GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN))
		return alloc_error;

	/* count should be less than 20 to prevent overflowing sg->length */
	GEM_BUG_ON(overflows_type(count * PAGE_SIZE, sg->length));

	/* Construct a table where each scatterlist contains different number
	 * of entries. The idea is to check that we can iterate the individual
	 * pages from inside the coalesced lists.
	 */
	pt->start = PFN_BIAS;
	pfn = pt->start;
	sg = pt->st.sgl;
	for (n = 0; n < count; n++) {
		unsigned long npages = npages_fn(n, count, rnd);

		/* Nobody expects the Sparse Memmap! */
		if (!page_contiguous(pfn_to_page(pfn),
				     pfn_to_page(pfn + npages),
				     npages)) {
			sg_free_table(&pt->st);
			return -ENOSPC;
		}

		if (n)
			sg = sg_next(sg);
		sg_set_page(sg, pfn_to_page(pfn), npages * PAGE_SIZE, 0);

		GEM_BUG_ON(page_to_pfn(sg_page(sg)) != pfn);
		GEM_BUG_ON(sg->length != npages * PAGE_SIZE);
		GEM_BUG_ON(sg->offset != 0);

		pfn += npages;
	}
	sg_mark_end(sg);
	pt->st.nents = n;
	pt->end = pfn;

	return 0;
}

static const npages_fn_t npages_funcs[] = {
	one,
	grow,
	shrink,
	random,
	random_page_size_pages,
	NULL,
};

static int igt_sg_alloc(void *ignored)
{
	IGT_TIMEOUT(end_time);
	const unsigned long max_order = 20; /* approximating a 4GiB object */
	struct rnd_state prng;
	unsigned long prime;
	int alloc_error = -ENOMEM;

	for_each_prime_number(prime, max_order) {
		unsigned long size = BIT(prime);
		int offset;

		for (offset = -1; offset <= 1; offset++) {
			unsigned long sz = size + offset;
			const npages_fn_t *npages;
			struct pfn_table pt;
			int err;

			for (npages = npages_funcs; *npages; npages++) {
				prandom_seed_state(&prng,
						   i915_selftest.random_seed);
				err = alloc_table(&pt, sz, sz, *npages, &prng,
						  alloc_error);
				if (err == -ENOSPC)
					break;
				if (err)
					return err;

				prandom_seed_state(&prng,
						   i915_selftest.random_seed);
				err = expect_pfn_sgtable(&pt, *npages, &prng,
							 "sg_alloc_table",
							 end_time);
				sg_free_table(&pt.st);
				if (err)
					return err;
			}
		}

		/* Test at least one continuation before accepting oom */
		if (size > SG_MAX_SINGLE_ALLOC)
			alloc_error = -ENOSPC;
	}

	return 0;
}

static int igt_sg_trim(void *ignored)
{
	IGT_TIMEOUT(end_time);
	const unsigned long max = PAGE_SIZE; /* not prime! */
	struct pfn_table pt;
	unsigned long prime;
	int alloc_error = -ENOMEM;

	for_each_prime_number(prime, max) {
		const npages_fn_t *npages;
		int err;

		for (npages = npages_funcs; *npages; npages++) {
			struct rnd_state prng;

			prandom_seed_state(&prng, i915_selftest.random_seed);
			err = alloc_table(&pt, prime, max, *npages, &prng,
					  alloc_error);
			if (err == -ENOSPC)
				break;
			if (err)
				return err;

			if (i915_sg_trim(&pt.st)) {
				if (pt.st.orig_nents != prime ||
				    pt.st.nents != prime) {
					pr_err("i915_sg_trim failed (nents %u, orig_nents %u), expected %lu\n",
					       pt.st.nents, pt.st.orig_nents, prime);
					err = -EINVAL;
				} else {
					prandom_seed_state(&prng,
							   i915_selftest.random_seed);
					err = expect_pfn_sgtable(&pt,
								 *npages, &prng,
								 "i915_sg_trim",
								 end_time);
				}
			}
			sg_free_table(&pt.st);
			if (err)
				return err;
		}

		/* Test at least one continuation before accepting oom */
		if (prime > SG_MAX_SINGLE_ALLOC)
			alloc_error = -ENOSPC;
	}

	return 0;
}

int scatterlist_mock_selftests(void)
{
	static const struct i915_subtest tests[] = {
		SUBTEST(igt_sg_alloc),
		SUBTEST(igt_sg_trim),
	};

	return i915_subtests(tests, NULL);
}