[PATCH v4] drm/i915: stop using swiotlb

* [PATCH v4] drm/i915: stop using swiotlb
@ 2022-07-25 14:18 ` Robert Beckett
  0 siblings, 0 replies; 13+ messages in thread
From: Robert Beckett @ 2022-07-25 14:18 UTC (permalink / raw)
  To: Jani Nikula, Joonas Lahtinen, Rodrigo Vivi, Tvrtko Ursulin,
	David Airlie, Daniel Vetter
  Cc: kernel, Robert Beckett, Christoph Hellwig, Thomas Hellstrom,
	Matthew Auld, Tvrtko Ursulin, intel-gfx, dri-devel, linux-kernel

Calling swiotlb functions directly is nowadays considered harmful. See
https://lore.kernel.org/intel-gfx/20220711082614.GA29487@lst.de/

Replace swiotlb_max_segment() calls with dma_max_mapping_size().
In i915_gem_object_get_pages_internal() no longer consider max_segment
only if CONFIG_SWIOTLB is enabled. There can be other (iommu related)
causes of specific max segment sizes.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Thomas Hellstrom <thomas.hellstrom@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>

v2: - restore UINT_MAX clamp in i915_sg_segment_size()
    - drop PAGE_SIZE check as it will always be >= PAGE_SIZE
v3: - actually clamp to UINT_MAX in i915_sg_segment_size()
v4: - round down max segment size to PAGE_SIZE

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Robert Beckett <bob.beckett@collabora.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_internal.c | 19 ++++---------------
 drivers/gpu/drm/i915/gem/i915_gem_shmem.c    |  2 +-
 drivers/gpu/drm/i915/gem/i915_gem_ttm.c      |  4 ++--
 drivers/gpu/drm/i915/gem/i915_gem_userptr.c  |  2 +-
 drivers/gpu/drm/i915/i915_scatterlist.h      | 17 ++++-------------
 5 files changed, 12 insertions(+), 32 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_internal.c b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
index c698f95af15f..24f37658f1bb 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_internal.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_internal.c
@@ -6,7 +6,6 @@
 
 #include <linux/scatterlist.h>
 #include <linux/slab.h>
-#include <linux/swiotlb.h>
 
 #include "i915_drv.h"
 #include "i915_gem.h"
@@ -38,22 +37,12 @@ static int i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)
 	struct scatterlist *sg;
 	unsigned int sg_page_sizes;
 	unsigned int npages;
-	int max_order;
+	int max_order = MAX_ORDER;
+	unsigned int max_segment;
 	gfp_t gfp;
 
-	max_order = MAX_ORDER;
-#ifdef CONFIG_SWIOTLB
-	if (is_swiotlb_active(obj->base.dev->dev)) {
-		unsigned int max_segment;
-
-		max_segment = swiotlb_max_segment();
-		if (max_segment) {
-			max_segment = max_t(unsigned int, max_segment,
-					    PAGE_SIZE) >> PAGE_SHIFT;
-			max_order = min(max_order, ilog2(max_segment));
-		}
-	}
-#endif
+	max_segment = i915_sg_segment_size(i915->drm.dev) >> PAGE_SHIFT;
+	max_order = min(max_order, ilog2(max_segment));
 
 	gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_RECLAIMABLE;
 	if (IS_I965GM(i915) || IS_I965G(i915)) {
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
index 4eed3dd90ba8..34b9c76cd8e6 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
@@ -194,7 +194,7 @@ static int shmem_get_pages(struct drm_i915_gem_object *obj)
 	struct intel_memory_region *mem = obj->mm.region;
 	struct address_space *mapping = obj->base.filp->f_mapping;
 	const unsigned long page_count = obj->base.size / PAGE_SIZE;
-	unsigned int max_segment = i915_sg_segment_size();
+	unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
 	struct sg_table *st;
 	struct sgt_iter sgt_iter;
 	struct page *page;
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index 5a5cf332d8a5..7a828c9c0f6d 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -189,7 +189,7 @@ static int i915_ttm_tt_shmem_populate(struct ttm_device *bdev,
 	struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev);
 	struct intel_memory_region *mr = i915->mm.regions[INTEL_MEMORY_SYSTEM];
 	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
-	const unsigned int max_segment = i915_sg_segment_size();
+	const unsigned int max_segment = i915_sg_segment_size(i915->drm.dev);
 	const size_t size = (size_t)ttm->num_pages << PAGE_SHIFT;
 	struct file *filp = i915_tt->filp;
 	struct sgt_iter sgt_iter;
@@ -568,7 +568,7 @@ static struct i915_refct_sgt *i915_ttm_tt_get_st(struct ttm_tt *ttm)
 	ret = sg_alloc_table_from_pages_segment(st,
 			ttm->pages, ttm->num_pages,
 			0, (unsigned long)ttm->num_pages << PAGE_SHIFT,
-			i915_sg_segment_size(), GFP_KERNEL);
+			i915_sg_segment_size(i915_tt->dev), GFP_KERNEL);
 	if (ret) {
 		st->sgl = NULL;
 		return ERR_PTR(ret);
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
index 094f06b4ce33..dfc35905dba2 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
@@ -129,7 +129,7 @@ static void i915_gem_object_userptr_drop_ref(struct drm_i915_gem_object *obj)
 static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
 {
 	const unsigned long num_pages = obj->base.size >> PAGE_SHIFT;
-	unsigned int max_segment = i915_sg_segment_size();
+	unsigned int max_segment = i915_sg_segment_size(obj->base.dev->dev);
 	struct sg_table *st;
 	unsigned int sg_page_sizes;
 	struct page **pvec;
diff --git a/drivers/gpu/drm/i915/i915_scatterlist.h b/drivers/gpu/drm/i915/i915_scatterlist.h
index 9ddb3e743a3e..1377a97a20cf 100644
--- a/drivers/gpu/drm/i915/i915_scatterlist.h
+++ b/drivers/gpu/drm/i915/i915_scatterlist.h
@@ -9,7 +9,7 @@
 
 #include <linux/pfn.h>
 #include <linux/scatterlist.h>
-#include <linux/swiotlb.h>
+#include <linux/dma-mapping.h>
 
 #include "i915_gem.h"
 
@@ -127,19 +127,10 @@ static inline unsigned int i915_sg_dma_sizes(struct scatterlist *sg)
 	return page_sizes;
 }
 
-static inline unsigned int i915_sg_segment_size(void)
+static inline unsigned int i915_sg_segment_size(struct device *dev)
 {
-	unsigned int size = swiotlb_max_segment();
-
-	if (size == 0)
-		size = UINT_MAX;
-
-	size = rounddown(size, PAGE_SIZE);
-	/* swiotlb_max_segment_size can return 1 byte when it means one page. */
-	if (size < PAGE_SIZE)
-		size = PAGE_SIZE;
-
-	return size;
+	size_t max = min_t(size_t, UINT_MAX, dma_max_mapping_size(dev));
+	return round_down(max, PAGE_SIZE);
 }
 
 bool i915_sg_trim(struct sg_table *orig_st);
-- 
2.25.1


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