Re: [Intel-gfx] [PATCH 2/5] drm/i915/ttm: Adjust gem flags and caching settings after a move

Thanks for reviewing, Matthew.

On 6/3/21 12:35 PM, Matthew Auld wrote:

On Wed, 2 Jun 2021 at 18:08, Thomas Hellström thomas.hellstrom@linux.intel.com wrote:

...

After a TTM move we need to update the i915 gem flags and caching settings to reflect the new placement. Also introduce gpu_binds_iomem() and cpu_maps_iomem() to clean up the various ways we previously used to detect this. Finally, initialize the TTM object reserved to be able to update flags and caching before anyone else gets hold of the object.

Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 112 +++++++++++++++++++----- 1 file changed, 90 insertions(+), 22 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c index ae12a2be11a2..c73c51755c20 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c @@ -70,6 +70,17 @@ static struct ttm_placement i915_sys_placement = { .busy_placement = &lmem0_sys_placement_flags[1], };

+static bool gpu_binds_iomem(struct ttm_resource *mem)

What does gpu_binds mean here? It's mapped though the GTT?

gpu_bind_XX would here translate to "make xx visible to the gpu", We could of course use the term "gpu_maps" if you think that fits better.

...

+{

•   return (mem->mem_type != TTM_PL_SYSTEM);
  

+}

+static bool cpu_maps_iomem(struct ttm_resource *mem) +{

•   /* Once / if we support GGTT, this is also false for cached ttm_tts */
  

•   return (mem->mem_type != TTM_PL_SYSTEM);
  

+}

Can drop the extra brackets.

...

• static void i915_ttm_adjust_lru(struct drm_i915_gem_object *obj);

  static struct ttm_tt *i915_ttm_tt_create(struct ttm_buffer_object *bo,

@@ -175,6 +186,41 @@ static void i915_ttm_free_cached_io_st(struct drm_i915_gem_object *obj) obj->ttm.cached_io_st = NULL; }

+static void +i915_ttm_adjust_domains_after_cpu_move(struct drm_i915_gem_object *obj) +{

•   struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
  

•   if (cpu_maps_iomem(&bo->mem) || bo->ttm->caching != ttm_cached) {
  

•           obj->write_domain = I915_GEM_DOMAIN_WC;
  

•           obj->read_domains = I915_GEM_DOMAIN_WC;
  

•   } else {
  

•           obj->write_domain = I915_GEM_DOMAIN_CPU;
  

•           obj->read_domains = I915_GEM_DOMAIN_CPU;
  

•   }
  

+}

+static void i915_ttm_adjust_gem_after_move(struct drm_i915_gem_object *obj) +{

•   struct drm_i915_private *i915 = to_i915(obj->base.dev);
  

•   struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
  

•   unsigned int cache_level;
  

•   obj->mem_flags &= ~(I915_BO_FLAG_STRUCT_PAGE | I915_BO_FLAG_IOMEM);
  

•   obj->mem_flags |= cpu_maps_iomem(&bo->mem) ? I915_BO_FLAG_IOMEM :
  

•           I915_BO_FLAG_STRUCT_PAGE;
  

•   if ((HAS_LLC(i915) || HAS_SNOOP(i915)) && !gpu_binds_iomem(&bo->mem) &&
  

I think all modern hw has support for snooping or the fast shared LLC. Are we expecting to hit this path for non-dgpu?

Not initially, no. Possibly later.

Also by default we will choose ttm_cached at least for platforms like dg1?

Not for evicted LMEM. They still have ttm_write_combine. User-space can still access those through mmap() while evicted.

Also pin_map() is still a separate interface at this point?

Yes, I had a comment on that in your caching patch that I reviewed, we need to make sure even for pin_map that we only map using the single supported caching attributes for the BO.

...

•       bo->ttm->caching == ttm_cached) {
  

•           cache_level = I915_CACHE_LLC;
  

•   } else {
  

•           cache_level = I915_CACHE_NONE;
  

•   }
  

•   i915_gem_object_set_cache_coherency(obj, cache_level);
  

+}

• static void i915_ttm_purge(struct drm_i915_gem_object *obj) { struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);

@@ -190,8 +236,10 @@ static void i915_ttm_purge(struct drm_i915_gem_object *obj)

     /* TTM's purge interface. Note that we might be reentering. */
     ret = ttm_bo_validate(bo, &place, &ctx);

•    if (!ret) {
  

•           obj->write_domain = 0;
  

•           obj->read_domains = 0;
  

•           i915_ttm_adjust_gem_after_move(obj);
             i915_ttm_free_cached_io_st(obj);
             obj->mm.madv = __I915_MADV_PURGED;
     }
  

@@ -273,12 +321,15 @@ i915_ttm_resource_get_st(struct drm_i915_gem_object *obj, struct ttm_resource *res) { struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);

•   struct ttm_resource_manager *man =
  

•           ttm_manager_type(bo->bdev, res->mem_type);
  
  

•   if (man->use_tt)
  

•   if (!gpu_binds_iomem(res))
             return i915_ttm_tt_get_st(bo->ttm);
  
  

•   /*
  

•    * If CPU mapping differs, we need to add the ttm_tt pages to
  

•    * the resulting st. Might make sense for GGTT.
  

•    */
  

•   GEM_WARN_ON(!cpu_maps_iomem(res));
     return intel_region_ttm_node_to_st(obj->mm.region, res->mm_node);
  

  }

@@ -290,8 +341,6 @@ static int i915_ttm_move(struct ttm_buffer_object *bo, bool evict, struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo); struct ttm_resource_manager *dst_man = ttm_manager_type(bo->bdev, dst_mem->mem_type);

•   struct ttm_resource_manager *src_man =
  

•           ttm_manager_type(bo->bdev, bo->mem.mem_type);
     struct intel_memory_region *dst_reg, *src_reg;
     union {
             struct ttm_kmap_iter_tt tt;
  

@@ -332,34 +381,36 @@ static int i915_ttm_move(struct ttm_buffer_object *bo, bool evict, if (IS_ERR(dst_st)) return PTR_ERR(dst_st);

•   /* If we start mapping GGTT, we can no longer use man::use_tt here. */
  

•   dst_iter = dst_man->use_tt ?
  

•   dst_iter = !cpu_maps_iomem(dst_mem) ?
             ttm_kmap_iter_tt_init(&_dst_iter.tt, bo->ttm) :
             ttm_kmap_iter_iomap_init(&_dst_iter.io, &dst_reg->iomap,
                                      dst_st, dst_reg->region.start);
  
  

•   src_iter = src_man->use_tt ?
  

•   src_iter = !cpu_maps_iomem(&bo->mem) ?
             ttm_kmap_iter_tt_init(&_src_iter.tt, bo->ttm) :
             ttm_kmap_iter_iomap_init(&_src_iter.io, &src_reg->iomap,
                                      obj->ttm.cached_io_st,
                                      src_reg->region.start);
  
     ttm_move_memcpy(bo, dst_mem->num_pages, dst_iter, src_iter);
  

•   /* Below dst_mem becomes bo->mem. */
     ttm_bo_move_sync_cleanup(bo, dst_mem);
  

•   i915_ttm_adjust_domains_after_cpu_move(obj);
     i915_ttm_free_cached_io_st(obj);
  
  

•   if (!dst_man->use_tt) {
  

•   if (gpu_binds_iomem(dst_mem) || cpu_maps_iomem(dst_mem)) {
             obj->ttm.cached_io_st = dst_st;
             obj->ttm.get_io_page.sg_pos = dst_st->sgl;
             obj->ttm.get_io_page.sg_idx = 0;
     }
  
  

•   i915_ttm_adjust_gem_after_move(obj);
     return 0;
  

  }

  static int i915_ttm_io_mem_reserve(struct ttm_device *bdev, struct ttm_resource *mem) {

•   if (mem->mem_type < I915_PL_LMEM0)
  

•   if (!cpu_maps_iomem(mem))
             return 0;
  
     mem->bus.caching = ttm_write_combined;
  

@@ -421,6 +472,16 @@ static int i915_ttm_get_pages(struct drm_i915_gem_object *obj) if (ret) return ret == -ENOSPC ? -ENXIO : ret;

•   i915_ttm_adjust_lru(obj);
  

•   if (bo->ttm && !ttm_tt_is_populated(bo->ttm)) {
  

•           ret = ttm_tt_populate(bo->bdev, bo->ttm, &ctx);
  

•           if (ret)
  

•                   return ret;
  

•           i915_ttm_adjust_domains_after_cpu_move(obj);
  

•           i915_ttm_adjust_gem_after_move(obj);
  

•   }
  

•    /* Object either has a page vector or is an iomem object */
     st = bo->ttm ? i915_ttm_tt_get_st(bo->ttm) : obj->ttm.cached_io_st;
     if (IS_ERR(st))
  

@@ -428,8 +489,6 @@ static int i915_ttm_get_pages(struct drm_i915_gem_object *obj)

     __i915_gem_object_set_pages(obj, st, i915_sg_dma_sizes(st->sgl));

•   i915_ttm_adjust_lru(obj);
  

•    return ret;
  

  }

@@ -563,6 +622,7 @@ static u64 i915_ttm_mmap_offset(struct drm_i915_gem_object *obj)

const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = { .name = "i915_gem_object_ttm",

•   .flags = I915_GEM_OBJECT_IS_SHRINKABLE,
  
     .get_pages = i915_ttm_get_pages,
     .put_pages = i915_ttm_put_pages,
  

@@ -599,6 +659,10 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem, { static struct lock_class_key lock_class; struct drm_i915_private *i915 = mem->i915;

•   struct ttm_operation_ctx ctx = {
  

•           .interruptible = true,
  

•           .no_wait_gpu = false,
  

•   };
     enum ttm_bo_type bo_type;
     size_t alignment = 0;
     int ret;
  

@@ -618,15 +682,14 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem, i915_gem_object_init(obj, &i915_gem_ttm_obj_ops, &lock_class, flags); i915_gem_object_init_memory_region(obj, mem); i915_gem_object_make_unshrinkable(obj);

•   obj->read_domains = I915_GEM_DOMAIN_WC | I915_GEM_DOMAIN_GTT;
  

•   obj->mem_flags |= I915_BO_FLAG_IOMEM;
  

•   i915_gem_object_set_cache_coherency(obj, I915_CACHE_NONE);
     INIT_RADIX_TREE(&obj->ttm.get_io_page.radix, GFP_KERNEL | __GFP_NOWARN);
     mutex_init(&obj->ttm.get_io_page.lock);
  
     bo_type = (obj->flags & I915_BO_ALLOC_USER) ? ttm_bo_type_device :
             ttm_bo_type_kernel;
  
  

•   obj->base.vma_node.driver_private = i915_gem_to_ttm(obj);
  

•    /*
      * If this function fails, it will call the destructor, but
      * our caller still owns the object. So no freeing in the
  

@@ -634,14 +697,19 @@ int __i915_gem_ttm_object_init(struct intel_memory_region *mem, * Similarly, in delayed_destroy, we can't call ttm_bo_put() * until successful initialization. */

•   obj->base.vma_node.driver_private = i915_gem_to_ttm(obj);
  

•   ret = ttm_bo_init(&i915->bdev, i915_gem_to_ttm(obj), size,
  

•                     bo_type, &i915_sys_placement, alignment,
  

•                     true, NULL, NULL, i915_ttm_bo_destroy);
  

•   ret = ttm_bo_init_reserved(&i915->bdev, i915_gem_to_ttm(obj), size,
  

•                              bo_type, &i915_sys_placement, alignment,
  

•                              &ctx, NULL, NULL, i915_ttm_bo_destroy);
  

•   if (ret)
  

•           goto out;
  
  

•   if (!ret)
  

•           obj->ttm.created = true;
  

•   obj->ttm.created = true;
  

•   i915_ttm_adjust_domains_after_cpu_move(obj);
  

•   i915_ttm_adjust_gem_after_move(obj);
  

•   i915_gem_object_unlock(obj);
  
  

+out: /* i915 wants -ENXIO when out of memory region space. */ return (ret == -ENOSPC) ? -ENXIO : ret; } -- 2.31.1

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