Re: [PATCH 03/37] drm/i915: Add some selftests for sg_table manipulation

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 11/01/2017 21:09, Chris Wilson wrote:
> Start exercising the scattergather lists, especially looking at
> iteration after coalescing.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem.c                    |  11 +-
>  .../gpu/drm/i915/selftests/i915_mock_selftests.h   |   1 +
>  drivers/gpu/drm/i915/selftests/scatterlist.c       | 255 +++++++++++++++++++++
>  3 files changed, 264 insertions(+), 3 deletions(-)
>  create mode 100644 drivers/gpu/drm/i915/selftests/scatterlist.c
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 4c6d40e28cf5..e88541b5b72b 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2219,17 +2219,17 @@ void __i915_gem_object_put_pages(struct drm_i915_gem_object *obj,
>  	mutex_unlock(&obj->mm.lock);
>  }
>
> -static void i915_sg_trim(struct sg_table *orig_st)
> +static bool i915_sg_trim(struct sg_table *orig_st)
>  {
>  	struct sg_table new_st;
>  	struct scatterlist *sg, *new_sg;
>  	unsigned int i;
>
>  	if (orig_st->nents == orig_st->orig_nents)
> -		return;
> +		return false;
>
>  	if (sg_alloc_table(&new_st, orig_st->nents, GFP_KERNEL | __GFP_NOWARN))
> -		return;
> +		return false;
>
>  	new_sg = new_st.sgl;
>  	for_each_sg(orig_st->sgl, sg, orig_st->nents, i) {
> @@ -2242,6 +2242,7 @@ static void i915_sg_trim(struct sg_table *orig_st)
>  	sg_free_table(orig_st);
>
>  	*orig_st = new_st;
> +	return true;
>  }
>
>  static struct sg_table *
> @@ -4892,3 +4893,7 @@ i915_gem_object_get_dma_address(struct drm_i915_gem_object *obj,
>  	sg = i915_gem_object_get_sg(obj, n, &offset);
>  	return sg_dma_address(sg) + (offset << PAGE_SHIFT);
>  }
> +
> +#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
> +#include "selftests/scatterlist.c"
> +#endif
> diff --git a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
> index 69e97a2ba4a6..5f0bdda42ed8 100644
> --- a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
> +++ b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
> @@ -9,3 +9,4 @@
>   * Tests are executed in order by igt/drv_selftest
>   */
>  selftest(sanitycheck, i915_mock_sanitycheck) /* keep first (igt selfcheck) */
> +selftest(scatterlist, scatterlist_mock_selftests)
> diff --git a/drivers/gpu/drm/i915/selftests/scatterlist.c b/drivers/gpu/drm/i915/selftests/scatterlist.c
> new file mode 100644
> index 000000000000..1573be8961bf
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/selftests/scatterlist.c
> @@ -0,0 +1,255 @@
> +/*
> + * 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 <linux/prime_numbers.h>
> +
> +#include "i915_selftest.h"
> +
> +#define PFN_BIAS (1 << 10)
> +
> +struct pfn_table {
> +	struct sg_table st;
> +	unsigned long start, end;
> +};
> +
> +static noinline int expect_pfn_sg(struct pfn_table *pt, const char *who)
> +{
> +	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);
> +
> +		if (page_to_pfn(page) != pfn) {
> +			pr_err("%s left pages out of order, expected pfn %lu, found pfn %lu (using for_each_sg)\n",
> +			       who, pfn, page_to_pfn(page));
> +			return -EINVAL;
> +		}
> +
> +		if (sg->length != (n + 1) * PAGE_SIZE) {
> +			pr_err("%s: %s copied wrong sg length, expected size %lu, found %u (using for_each_sg)\n",
> +			       __func__, who, (n + 1) * PAGE_SIZE, sg->length);
> +			return -EINVAL;
> +		}
> +
> +		cond_resched();
> +		if (signal_pending(current))
> +			return -EINTR;
> +
> +		pfn += n + 1;
> +	}
> +	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)
> +{
> +	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;
> +		}
> +
> +		cond_resched();
> +		if (signal_pending(current))
> +			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)
> +{
> +	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;
> +		}
> +
> +		cond_resched();
> +		if (signal_pending(current))
> +			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, const char *who)
> +{
> +	int err;
> +
> +	err = expect_pfn_sg(pt, who);
> +	if (err)
> +		return err;
> +
> +	err = expect_pfn_sg_page_iter(pt, who);
> +	if (err)
> +		return err;
> +
> +	err = expect_pfn_sgtiter(pt, who);
> +	if (err)
> +		return err;
> +
> +	return 0;
> +}
> +
> +static bool alloc_table(struct pfn_table *pt,
> +			unsigned long count,
> +			unsigned long max)
> +{
> +	struct scatterlist *sg;
> +	unsigned long n, pfn;
> +
> +	if (sg_alloc_table(&pt->st, max,
> +			   GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN))
> +		return false;
> +
> +	pt->start = PFN_BIAS;
> +	pfn = pt->start;
> +	sg = pt->st.sgl;
> +	for (n = 0; n < count; n++) {
> +		if (n)
> +			sg = sg_next(sg);
> +		sg_set_page(sg, pfn_to_page(pfn), (n + 1)*PAGE_SIZE, 0);

For count = BIT(max_order) (== 1M) the last sg entry will have a size of 
4GiB which would overflow sg->length, no? Especially with size + offset 
below. Unless for_each_prime_number stops below max_order. But where?

> +		pfn += n + 1;

Please describe what kind of table and why you are building with a 
comment. If tests have no comments and do, on the first look, not fully 
obvious things, then it is a lot of effort in the future to work on 
fixes and/or maintain the code.

> +	}
> +	sg_mark_end(sg);
> +	pt->st.nents = n;
> +	pt->end = pfn;
> +
> +	return true;
> +}
> +
> +static int igt_sg_alloc(void *ignored)
> +{
> +	I915_SELFTEST_TIMEOUT(end_time);
> +	const unsigned long max_order = 20; /* approximating a 4GiB object */
> +	unsigned long prime;
> +
> +	for_each_prime_number(prime, max_order) {
> +		unsigned long size = BIT(prime);
> +		int offset;
> +
> +		for (offset = -1; offset <= 1; offset++) {
> +			struct pfn_table pt;
> +			int err;
> +
> +			if (!alloc_table(&pt, size + offset, size + offset))
> +				return 0; /* out of memory, give up */
> +
> +			err = expect_pfn_sgtable(&pt, "sg_alloc_table");
> +			sg_free_table(&pt.st);
> +			if (err)
> +				return err;
> +
> +			if (time_after(jiffies, end_time)) {
> +				pr_warn("%s timed out: last table size %lu\n",
> +					__func__, size + offset);
> +				return 0;
> +			}

Maybe a fmt+vaarg timeout helper since I expect there'll be a lot of 
this. Like:

if (i915_selftest_timeout(end_time, "fmt %s", arg))
	return 0;

It is slightly tidier.

> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static int igt_sg_trim(void *ignored)
> +{
> +	I915_SELFTEST_TIMEOUT(end_time);
> +	const unsigned long max = PAGE_SIZE; /* not prime! */
> +	struct pfn_table pt;
> +	unsigned long prime;
> +
> +	for_each_prime_number(prime, max) {
> +		int err;
> +
> +		if (!alloc_table(&pt, prime, max))
> +			return 0; /* out of memory, give up */
> +
> +		err = 0;
> +		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 {
> +				err = expect_pfn_sgtable(&pt, "i915_sg_trim");
> +			}
> +		}
> +		sg_free_table(&pt.st);
> +		if (err)
> +			return err;
> +
> +		if (time_after(jiffies, end_time)) {
> +			pr_warn("%s timed out: last trim size %lu/%lu\n",
> +				__func__, prime, max);
> +			return 0;
> +		}
> +	}
> +
> +	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);
> +}
>

Regards,

Tvrtko
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