drm/i915: Differentiate between ggtt->mutex and ppgtt->mutex

We have two classes of VM, global GTT and per-process GTT. In order to
allow ourselves the freedom to mix both along call chains, distinguish
the two classes with regards to their mutex and lockdep maps.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190114215956.32266-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -473,15 +473,15 @@ static void vm_free_page(struct i915_address_space *vm, struct page *page)
 	spin_unlock(&vm->free_pages.lock);
 }
 
-static void i915_address_space_init(struct i915_address_space *vm,
-				    struct drm_i915_private *dev_priv)
+static void i915_address_space_init(struct i915_address_space *vm, int subclass)
 {
 	/*
 	 * The vm->mutex must be reclaim safe (for use in the shrinker).
 	 * Do a dummy acquire now under fs_reclaim so that any allocation
 	 * attempt holding the lock is immediately reported by lockdep.
 	 */
 	mutex_init(&vm->mutex);
+	lockdep_set_subclass(&vm->mutex, subclass);
 	i915_gem_shrinker_taints_mutex(vm->i915, &vm->mutex);
 
 	GEM_BUG_ON(!vm->total);
@@ -1547,7 +1547,7 @@ static struct i915_hw_ppgtt *gen8_ppgtt_create(struct drm_i915_private *i915)
 	/* From bdw, there is support for read-only pages in the PPGTT. */
 	ppgtt->vm.has_read_only = true;
 
-	i915_address_space_init(&ppgtt->vm, i915);
+	i915_address_space_init(&ppgtt->vm, VM_CLASS_PPGTT);
 
 	/* There are only few exceptions for gen >=6. chv and bxt.
 	 * And we are not sure about the latter so play safe for now.
@@ -1996,7 +1996,7 @@ static struct i915_hw_ppgtt *gen6_ppgtt_create(struct drm_i915_private *i915)
 
 	ppgtt->base.vm.total = I915_PDES * GEN6_PTES * I915_GTT_PAGE_SIZE;
 
-	i915_address_space_init(&ppgtt->base.vm, i915);
+	i915_address_space_init(&ppgtt->base.vm, VM_CLASS_PPGTT);
 
 	ppgtt->base.vm.allocate_va_range = gen6_alloc_va_range;
 	ppgtt->base.vm.clear_range = gen6_ppgtt_clear_range;
@@ -3433,7 +3433,7 @@ int i915_ggtt_init_hw(struct drm_i915_private *dev_priv)
 	 * and beyond the end of the GTT if we do not provide a guard.
 	 */
 	mutex_lock(&dev_priv->drm.struct_mutex);
-	i915_address_space_init(&ggtt->vm, dev_priv);
+	i915_address_space_init(&ggtt->vm, VM_CLASS_GGTT);
 
 	ggtt->vm.is_ggtt = true;
 

drivers/gpu/drm/i915/i915_gem_gtt.h

@@ -288,6 +288,8 @@ struct i915_address_space {
 	bool closed;
 
 	struct mutex mutex; /* protects vma and our lists */
+#define VM_CLASS_GGTT 0
+#define VM_CLASS_PPGTT 1
 
 	u64 scratch_pte;
 	struct i915_page_dma scratch_page;

drivers/gpu/drm/i915/selftests/mock_gtt.c

@@ -70,7 +70,7 @@ mock_ppgtt(struct drm_i915_private *i915,
 	ppgtt->vm.total = round_down(U64_MAX, PAGE_SIZE);
 	ppgtt->vm.file = ERR_PTR(-ENODEV);
 
-	i915_address_space_init(&ppgtt->vm, i915);
+	i915_address_space_init(&ppgtt->vm, VM_CLASS_PPGTT);
 
 	ppgtt->vm.clear_range = nop_clear_range;
 	ppgtt->vm.insert_page = mock_insert_page;
@@ -102,6 +102,7 @@ void mock_init_ggtt(struct drm_i915_private *i915)
 	struct i915_ggtt *ggtt = &i915->ggtt;
 
 	ggtt->vm.i915 = i915;
+	ggtt->vm.is_ggtt = true;
 
 	ggtt->gmadr = (struct resource) DEFINE_RES_MEM(0, 2048 * PAGE_SIZE);
 	ggtt->mappable_end = resource_size(&ggtt->gmadr);
@@ -117,9 +118,8 @@ void mock_init_ggtt(struct drm_i915_private *i915)
 	ggtt->vm.vma_ops.set_pages   = ggtt_set_pages;
 	ggtt->vm.vma_ops.clear_pages = clear_pages;
 
-	i915_address_space_init(&ggtt->vm, i915);
 
-	ggtt->vm.is_ggtt = true;
+	i915_address_space_init(&ggtt->vm, VM_CLASS_GGTT);
 }
 
 void mock_fini_ggtt(struct drm_i915_private *i915)