drm/i915/gem: Split eb_vma into its own allocation

Use a separate array allocation for the execbuf vma, so that we can
track their lifetime independently from the copy of the user arguments.
With luck, this has a secondary benefit of splitting the malloc size to
within reason and avoid vmalloc. The downside is that we might require
two separate vmallocs -- but much less likely.

In the process, this prevents a memory leak on the ww_mutex error
unwind.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1390Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200330133710.14385-1-chris@chris-wilson.co.uk

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

@@ -40,6 +40,11 @@ struct eb_vma {
 	u32 handle;
 };
 
+struct eb_vma_array {
+	struct kref kref;
+	struct eb_vma vma[];
+};
+
 enum {
 	FORCE_CPU_RELOC = 1,
 	FORCE_GTT_RELOC,
@@ -52,7 +57,6 @@ enum {
 #define __EXEC_OBJECT_NEEDS_MAP		BIT(29)
 #define __EXEC_OBJECT_NEEDS_BIAS	BIT(28)
 #define __EXEC_OBJECT_INTERNAL_FLAGS	(~0u << 28) /* all of the above */
-#define __EXEC_OBJECT_RESERVED (__EXEC_OBJECT_HAS_PIN | __EXEC_OBJECT_HAS_FENCE)
 
 #define __EXEC_HAS_RELOC	BIT(31)
 #define __EXEC_INTERNAL_FLAGS	(~0u << 31)
@@ -283,6 +287,7 @@ struct i915_execbuffer {
 	 */
 	int lut_size;
 	struct hlist_head *buckets; /** ht for relocation handles */
+	struct eb_vma_array *array;
 };
 
 static inline bool eb_use_cmdparser(const struct i915_execbuffer *eb)
@@ -292,8 +297,62 @@ static inline bool eb_use_cmdparser(const struct i915_execbuffer *eb)
 		 eb->args->batch_len);
 }
 
+static struct eb_vma_array *eb_vma_array_create(unsigned int count)
+{
+	struct eb_vma_array *arr;
+
+	arr = kvmalloc(struct_size(arr, vma, count), GFP_KERNEL | __GFP_NOWARN);
+	if (!arr)
+		return NULL;
+
+	kref_init(&arr->kref);
+	arr->vma[0].vma = NULL;
+
+	return arr;
+}
+
+static inline void eb_unreserve_vma(struct eb_vma *ev)
+{
+	struct i915_vma *vma = ev->vma;
+
+	if (unlikely(ev->flags & __EXEC_OBJECT_HAS_FENCE))
+		__i915_vma_unpin_fence(vma);
+
+	if (ev->flags & __EXEC_OBJECT_HAS_PIN)
+		__i915_vma_unpin(vma);
+
+	ev->flags &= ~(__EXEC_OBJECT_HAS_PIN |
+		       __EXEC_OBJECT_HAS_FENCE);
+}
+
+static void eb_vma_array_destroy(struct kref *kref)
+{
+	struct eb_vma_array *arr = container_of(kref, typeof(*arr), kref);
+	struct eb_vma *ev = arr->vma;
+
+	while (ev->vma) {
+		eb_unreserve_vma(ev);
+		i915_vma_put(ev->vma);
+		ev++;
+	}
+
+	kvfree(arr);
+}
+
+static void eb_vma_array_put(struct eb_vma_array *arr)
+{
+	kref_put(&arr->kref, eb_vma_array_destroy);
+}
+
 static int eb_create(struct i915_execbuffer *eb)
 {
+	/* Allocate an extra slot for use by the command parser + sentinel */
+	eb->array = eb_vma_array_create(eb->buffer_count + 2);
+	if (!eb->array)
+		return -ENOMEM;
+
+	eb->vma = eb->array->vma;
+
 	if (!(eb->args->flags & I915_EXEC_HANDLE_LUT)) {
 		unsigned int size = 1 + ilog2(eb->buffer_count);
 
@@ -327,8 +386,10 @@ static int eb_create(struct i915_execbuffer *eb)
 				break;
 		} while (--size);
 
-		if (unlikely(!size))
+		if (unlikely(!size)) {
+			eb_vma_array_put(eb->array);
 			return -ENOMEM;
+		}
 
 		eb->lut_size = size;
 	} else {
@@ -402,26 +463,6 @@ eb_pin_vma(struct i915_execbuffer *eb,
 	return !eb_vma_misplaced(entry, vma, ev->flags);
 }
 
-static inline void __eb_unreserve_vma(struct i915_vma *vma, unsigned int flags)
-{
-	GEM_BUG_ON(!(flags & __EXEC_OBJECT_HAS_PIN));
-
-	if (unlikely(flags & __EXEC_OBJECT_HAS_FENCE))
-		__i915_vma_unpin_fence(vma);
-
-	__i915_vma_unpin(vma);
-}
-
-static inline void
-eb_unreserve_vma(struct eb_vma *ev)
-{
-	if (!(ev->flags & __EXEC_OBJECT_HAS_PIN))
-		return;
-
-	__eb_unreserve_vma(ev->vma, ev->flags);
-	ev->flags &= ~__EXEC_OBJECT_RESERVED;
-}
-
 static int
 eb_validate_vma(struct i915_execbuffer *eb,
 		struct drm_i915_gem_exec_object2 *entry,
@@ -863,31 +904,13 @@ eb_get_vma(const struct i915_execbuffer *eb, unsigned long handle)
 	}
 }
 
-static void eb_release_vmas(const struct i915_execbuffer *eb)
-{
-	const unsigned int count = eb->buffer_count;
-	unsigned int i;
-
-	for (i = 0; i < count; i++) {
-		struct eb_vma *ev = &eb->vma[i];
-		struct i915_vma *vma = ev->vma;
-
-		if (!vma)
-			break;
-
-		eb->vma[i].vma = NULL;
-
-		if (ev->flags & __EXEC_OBJECT_HAS_PIN)
-			__eb_unreserve_vma(vma, ev->flags);
-
-		i915_vma_put(vma);
-	}
-}
-
 static void eb_destroy(const struct i915_execbuffer *eb)
 {
 	GEM_BUG_ON(eb->reloc_cache.rq);
 
+	if (eb->array)
+		eb_vma_array_put(eb->array);
+
 	if (eb->lut_size > 0)
 		kfree(eb->buckets);
 }
@@ -1635,19 +1658,15 @@ static int eb_move_to_gpu(struct i915_execbuffer *eb)
 			err = i915_vma_move_to_active(vma, eb->request, flags);
 
 		i915_vma_unlock(vma);
-
-		__eb_unreserve_vma(vma, flags);
-		i915_vma_put(vma);
-
-		ev->vma = NULL;
+		eb_unreserve_vma(ev);
 	}
 	ww_acquire_fini(&acquire);
 
+	eb_vma_array_put(fetch_and_zero(&eb->array));
+
 	if (unlikely(err))
 		goto err_skip;
 
-	eb->exec = NULL;
-
 	/* Unconditionally flush any chipset caches (for streaming writes). */
 	intel_gt_chipset_flush(eb->engine->gt);
 	return 0;
@@ -1899,6 +1918,7 @@ static int eb_parse(struct i915_execbuffer *eb)
 	eb->vma[eb->buffer_count].vma = i915_vma_get(shadow);
 	eb->vma[eb->buffer_count].flags = __EXEC_OBJECT_HAS_PIN;
 	eb->batch = &eb->vma[eb->buffer_count++];
+	eb->vma[eb->buffer_count].vma = NULL;
 
 	eb->trampoline = trampoline;
 	eb->batch_start_offset = 0;
@@ -2422,8 +2442,6 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 		args->flags |= __EXEC_HAS_RELOC;
 
 	eb.exec = exec;
-	eb.vma = (struct eb_vma *)(exec + args->buffer_count + 1);
-	eb.vma[0].vma = NULL;
 
 	eb.invalid_flags = __EXEC_OBJECT_UNKNOWN_FLAGS;
 	reloc_cache_init(&eb.reloc_cache, eb.i915);
@@ -2630,8 +2648,6 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 	if (batch->private)
 		intel_engine_pool_put(batch->private);
 err_vma:
-	if (eb.exec)
-		eb_release_vmas(&eb);
 	if (eb.trampoline)
 		i915_vma_unpin(eb.trampoline);
 	eb_unpin_engine(&eb);
@@ -2651,7 +2667,7 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 
 static size_t eb_element_size(void)
 {
-	return sizeof(struct drm_i915_gem_exec_object2) + sizeof(struct eb_vma);
+	return sizeof(struct drm_i915_gem_exec_object2);
 }
 
 static bool check_buffer_count(size_t count)
@@ -2707,7 +2723,7 @@ i915_gem_execbuffer_ioctl(struct drm_device *dev, void *data,
 	/* Copy in the exec list from userland */
 	exec_list = kvmalloc_array(count, sizeof(*exec_list),
 				   __GFP_NOWARN | GFP_KERNEL);
-	exec2_list = kvmalloc_array(count + 1, eb_element_size(),
+	exec2_list = kvmalloc_array(count, eb_element_size(),
 				    __GFP_NOWARN | GFP_KERNEL);
 	if (exec_list == NULL || exec2_list == NULL) {
 		drm_dbg(&i915->drm,
@@ -2785,8 +2801,7 @@ i915_gem_execbuffer2_ioctl(struct drm_device *dev, void *data,
 	if (err)
 		return err;
 
-	/* Allocate an extra slot for use by the command parser */
-	exec2_list = kvmalloc_array(count + 1, eb_element_size(),
+	exec2_list = kvmalloc_array(count, eb_element_size(),
 				    __GFP_NOWARN | GFP_KERNEL);
 	if (exec2_list == NULL) {
 		drm_dbg(&i915->drm, "Failed to allocate exec list for %zd buffers\n",