Messages in this thread | | | Date | Fri, 22 Jul 2022 10:45:54 +0100 | Subject | Re: [PATCH] drm/i915: stop using swiotlb | From | Tvrtko Ursulin <> |
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On 21/07/2022 18:43, Robert Beckett wrote: > 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> > > Signed-off-by: Robert Beckett <bob.beckett@collabora.com> > --- > drivers/gpu/drm/i915/gem/i915_gem_internal.c | 20 +++++--------------- > 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 | 16 ---------------- > 5 files changed, 9 insertions(+), 35 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..e1aca378d90f 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 +37,13 @@ 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; > + size_t 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 = dma_max_mapping_size(i915->drm.dev); > + max_segment = max_t(size_t, max_segment, PAGE_SIZE) >> 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..b0ec65b7c1da 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 = dma_max_mapping_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..882f046f4d18 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 = dma_max_mapping_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); > + dma_max_mapping_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..8a62a71859e6 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 = dma_max_mapping_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..c9a61b51e99d 100644 > --- a/drivers/gpu/drm/i915/i915_scatterlist.h > +++ b/drivers/gpu/drm/i915/i915_scatterlist.h > @@ -9,7 +9,6 @@ > > #include <linux/pfn.h> > #include <linux/scatterlist.h> > -#include <linux/swiotlb.h> > > #include "i915_gem.h" > > @@ -127,21 +126,6 @@ static inline unsigned int i915_sg_dma_sizes(struct scatterlist *sg) > return page_sizes; > } > > -static inline unsigned int i915_sg_segment_size(void) > -{ > - unsigned int size = swiotlb_max_segment(); > - > - if (size == 0) > - size = UINT_MAX;
On a more detailed look, there was a CI failure which makes me think this cap might need to stay. Because max sg segment is unsigned int. So I wonder if sg contstruction overflows without it.
If this quick analysis is right, you could leave i915_sg_segment_size helper and cap the return from dma_max_mapping_size to UINT_MAX in it.
Regards,
Tvrtko
*) https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_106589v1/shard-tglb2/igt@gem_mmap_offset@clear.html
> - > - 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; > -} > - > bool i915_sg_trim(struct sg_table *orig_st); > > /**
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