Commit c2ea703d authored by Thomas Hellström's avatar Thomas Hellström
Browse files

drm/i915: Require the vm mutex for i915_vma_bind() 



Protect updates of struct i915_vma flags and async binding / unbinding
with the vm::mutex. This means that i915_vma_bind() needs to assert
vm::mutex held. In order to make that possible drop the caching of
kmap_atomic() maps around i915_vma_bind().

An alternative would be to use kmap_local() but since we block cpu
unplugging during sleeps inside kmap_local() sections this may have
unwanted side-effects. Particularly since we might wait for gpu while
holding the vm mutex.

This change may theoretically increase execbuf cpu-usage on snb, but
at least on non-highmem systems that increase should be very small.

Signed-off-by: default avatarThomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: default avatarMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211221200050.436316-5-thomas.hellstrom@linux.intel.com
parent 63cf4cad

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

+49 −1
Original line number Diff line number Diff line
@@ -1098,6 +1098,47 @@ static inline struct i915_ggtt *cache_to_ggtt(struct reloc_cache *cache) 
	return &i915->ggtt;

}



static void reloc_cache_unmap(struct reloc_cache *cache)

{

	void *vaddr;



	if (!cache->vaddr)

		return;



	vaddr = unmask_page(cache->vaddr);

	if (cache->vaddr & KMAP)

		kunmap_atomic(vaddr);

	else

		io_mapping_unmap_atomic((void __iomem *)vaddr);

}



static void reloc_cache_remap(struct reloc_cache *cache,

			      struct drm_i915_gem_object *obj)

{

	void *vaddr;



	if (!cache->vaddr)

		return;



	if (cache->vaddr & KMAP) {

		struct page *page = i915_gem_object_get_page(obj, cache->page);



		vaddr = kmap_atomic(page);

		cache->vaddr = unmask_flags(cache->vaddr) |

			(unsigned long)vaddr;

	} else {

		struct i915_ggtt *ggtt = cache_to_ggtt(cache);

		unsigned long offset;



		offset = cache->node.start;

		if (!drm_mm_node_allocated(&cache->node))

			offset += cache->page << PAGE_SHIFT;



		cache->vaddr = (unsigned long)

			io_mapping_map_atomic_wc(&ggtt->iomap, offset);

	}

}



static void reloc_cache_reset(struct reloc_cache *cache, struct i915_execbuffer *eb)

{

	void *vaddr;
@@ -1362,10 +1403,17 @@ eb_relocate_entry(struct i915_execbuffer *eb, 
		 * batchbuffers.

		 */

		if (reloc->write_domain == I915_GEM_DOMAIN_INSTRUCTION &&

		    GRAPHICS_VER(eb->i915) == 6) {

		    GRAPHICS_VER(eb->i915) == 6 &&

		    !i915_vma_is_bound(target->vma, I915_VMA_GLOBAL_BIND)) {

			struct i915_vma *vma = target->vma;



			reloc_cache_unmap(&eb->reloc_cache);

			mutex_lock(&vma->vm->mutex);

			err = i915_vma_bind(target->vma,

					    target->vma->obj->cache_level,

					    PIN_GLOBAL, NULL);

			mutex_unlock(&vma->vm->mutex);

			reloc_cache_remap(&eb->reloc_cache, ev->vma->obj);

			if (err)

				return err;

		}

drivers/gpu/drm/i915/i915_vma.c

+1 −0
Original line number Diff line number Diff line
@@ -393,6 +393,7 @@ int i915_vma_bind(struct i915_vma *vma, 
	u32 bind_flags;

	u32 vma_flags;



	lockdep_assert_held(&vma->vm->mutex);

	GEM_BUG_ON(!drm_mm_node_allocated(&vma->node));

	GEM_BUG_ON(vma->size > vma->node.size);