diff options
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem.c | 99 |
1 files changed, 78 insertions, 21 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 1e67484fd5dc..e57061ac0219 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -3657,53 +3657,106 @@ i915_gem_object_set_to_gtt_domain(struct drm_i915_gem_object *obj, bool write) return 0; } +/** + * Changes the cache-level of an object across all VMA. + * + * After this function returns, the object will be in the new cache-level + * across all GTT and the contents of the backing storage will be coherent, + * with respect to the new cache-level. In order to keep the backing storage + * coherent for all users, we only allow a single cache level to be set + * globally on the object and prevent it from being changed whilst the + * hardware is reading from the object. That is if the object is currently + * on the scanout it will be set to uncached (or equivalent display + * cache coherency) and all non-MOCS GPU access will also be uncached so + * that all direct access to the scanout remains coherent. + */ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj, enum i915_cache_level cache_level) { struct drm_device *dev = obj->base.dev; struct i915_vma *vma, *next; + bool bound = false; int ret = 0; if (obj->cache_level == cache_level) goto out; - if (i915_gem_obj_is_pinned(obj)) { - DRM_DEBUG("can not change the cache level of pinned objects\n"); - return -EBUSY; - } - + /* Inspect the list of currently bound VMA and unbind any that would + * be invalid given the new cache-level. This is principally to + * catch the issue of the CS prefetch crossing page boundaries and + * reading an invalid PTE on older architectures. + */ list_for_each_entry_safe(vma, next, &obj->vma_list, vma_link) { + if (!drm_mm_node_allocated(&vma->node)) + continue; + + if (vma->pin_count) { + DRM_DEBUG("can not change the cache level of pinned objects\n"); + return -EBUSY; + } + if (!i915_gem_valid_gtt_space(vma, cache_level)) { ret = i915_vma_unbind(vma); if (ret) return ret; - } + } else + bound = true; } - if (i915_gem_obj_bound_any(obj)) { + /* We can reuse the existing drm_mm nodes but need to change the + * cache-level on the PTE. We could simply unbind them all and + * rebind with the correct cache-level on next use. However since + * we already have a valid slot, dma mapping, pages etc, we may as + * rewrite the PTE in the belief that doing so tramples upon less + * state and so involves less work. + */ + if (bound) { + /* Before we change the PTE, the GPU must not be accessing it. + * If we wait upon the object, we know that all the bound + * VMA are no longer active. + */ ret = i915_gem_object_wait_rendering(obj, false); if (ret) return ret; - i915_gem_object_finish_gtt(obj); - - /* Before SandyBridge, you could not use tiling or fence - * registers with snooped memory, so relinquish any fences - * currently pointing to our region in the aperture. - */ - if (INTEL_INFO(dev)->gen < 6) { + if (!HAS_LLC(dev) && cache_level != I915_CACHE_NONE) { + /* Access to snoopable pages through the GTT is + * incoherent and on some machines causes a hard + * lockup. Relinquish the CPU mmaping to force + * userspace to refault in the pages and we can + * then double check if the GTT mapping is still + * valid for that pointer access. + */ + i915_gem_release_mmap(obj); + + /* As we no longer need a fence for GTT access, + * we can relinquish it now (and so prevent having + * to steal a fence from someone else on the next + * fence request). Note GPU activity would have + * dropped the fence as all snoopable access is + * supposed to be linear. + */ ret = i915_gem_object_put_fence(obj); if (ret) return ret; + } else { + /* We either have incoherent backing store and + * so no GTT access or the architecture is fully + * coherent. In such cases, existing GTT mmaps + * ignore the cache bit in the PTE and we can + * rewrite it without confusing the GPU or having + * to force userspace to fault back in its mmaps. + */ } - list_for_each_entry(vma, &obj->vma_list, vma_link) - if (drm_mm_node_allocated(&vma->node)) { - ret = i915_vma_bind(vma, cache_level, - PIN_UPDATE); - if (ret) - return ret; - } + list_for_each_entry(vma, &obj->vma_list, vma_link) { + if (!drm_mm_node_allocated(&vma->node)) + continue; + + ret = i915_vma_bind(vma, cache_level, PIN_UPDATE); + if (ret) + return ret; + } } list_for_each_entry(vma, &obj->vma_list, vma_link) @@ -3711,6 +3764,10 @@ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj, obj->cache_level = cache_level; out: + /* Flush the dirty CPU caches to the backing storage so that the + * object is now coherent at its new cache level (with respect + * to the access domain). + */ if (obj->cache_dirty && obj->base.write_domain != I915_GEM_DOMAIN_CPU && cpu_write_needs_clflush(obj)) { |