drm/i915: return the correct usable aperture size under gvt environment

I915_GEM_GET_APERTURE ioctl is used to probe aperture size from userspace.
In gvt environment, each vm only use the ballooned part of aperture, so we
should return the correct available aperture size exclude the reserved part
by balloon.

v2: add 'reserved' in struct i915_address_space to record the reserved size
in ggtt (Chris)

v3: remain aper_size as total, adjust aper_available_size exclude reserved
and pinned. UMD driver need to adjust the max allocation size according to
the available aperture size but not total size. KMD return the correct
usable aperture size any time (Chris, Joonas)

v4: decrease reserved in deballoon (Joonas)

v5: add onion teardown in balloon, add vgt_deballoon_space (Joonas)

v6: change title name (Zhenyu)

v7: code style refine (Joonas)

Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Suggested-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Weinan Li <weinan.z.li@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1496198152-14175-1-git-send-email-weinan.z.li@intel.com
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/i915_gem.c

@@ -143,9 +143,9 @@ i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
 	struct i915_ggtt *ggtt = &dev_priv->ggtt;
 	struct drm_i915_gem_get_aperture *args = data;
 	struct i915_vma *vma;
-	size_t pinned;
+	u64 pinned;
 
-	pinned = 0;
+	pinned = ggtt->base.reserved;
 	mutex_lock(&dev->struct_mutex);
 	list_for_each_entry(vma, &ggtt->base.active_list, vm_link)
 		if (i915_vma_is_pinned(vma))

drivers/gpu/drm/i915/i915_gem_gtt.h

@@ -255,6 +255,7 @@ struct i915_address_space {
 	struct drm_i915_file_private *file;
 	struct list_head global_link;
 	u64 total;		/* size addr space maps (ex. 2GB for ggtt) */
+	u64 reserved;		/* size addr space reserved */
 
 	bool closed;
 

drivers/gpu/drm/i915/i915_vgpu.c

@@ -92,6 +92,18 @@ struct _balloon_info_ {
 
 static struct _balloon_info_ bl_info;
 
+static void vgt_deballoon_space(struct i915_ggtt *ggtt,
+				struct drm_mm_node *node)
+{
+	DRM_DEBUG_DRIVER("deballoon space: range [0x%llx - 0x%llx] %llu KiB.\n",
+			 node->start,
+			 node->start + node->size,
+			 node->size / 1024);
+
+	ggtt->base.reserved -= node->size;
+	drm_mm_remove_node(node);
+}
+
 /**
  * intel_vgt_deballoon - deballoon reserved graphics address trunks
  * @dev_priv: i915 device private data
@@ -108,12 +120,8 @@ void intel_vgt_deballoon(struct drm_i915_private *dev_priv)
 
 	DRM_DEBUG("VGT deballoon.\n");
 
-	for (i = 0; i < 4; i++) {
-		if (bl_info.space[i].allocated)
-			drm_mm_remove_node(&bl_info.space[i]);
-	}
-
-	memset(&bl_info, 0, sizeof(bl_info));
+	for (i = 0; i < 4; i++)
+		vgt_deballoon_space(&dev_priv->ggtt, &bl_info.space[i]);
 }
 
 static int vgt_balloon_space(struct i915_ggtt *ggtt,
@@ -121,15 +129,20 @@ static int vgt_balloon_space(struct i915_ggtt *ggtt,
 			     unsigned long start, unsigned long end)
 {
 	unsigned long size = end - start;
+	int ret;
 
 	if (start >= end)
 		return -EINVAL;
 
 	DRM_INFO("balloon space: range [ 0x%lx - 0x%lx ] %lu KiB.\n",
 		 start, end, size / 1024);
-	return i915_gem_gtt_reserve(&ggtt->base, node,
-				    size, start, I915_COLOR_UNEVICTABLE,
-				    0);
+	ret = i915_gem_gtt_reserve(&ggtt->base, node,
+				   size, start, I915_COLOR_UNEVICTABLE,
+				   0);
+	if (!ret)
+		ggtt->base.reserved += size;
+
+	return ret;
 }
 
 /**
@@ -222,7 +235,7 @@ int intel_vgt_balloon(struct drm_i915_private *dev_priv)
 		ret = vgt_balloon_space(ggtt, &bl_info.space[3],
 					unmappable_end, ggtt_end);
 		if (ret)
-			goto err;
+			goto err_upon_mappable;
 	}
 
 	/* Mappable graphic memory ballooning */
@@ -231,7 +244,7 @@ int intel_vgt_balloon(struct drm_i915_private *dev_priv)
 					0, mappable_base);
 
 		if (ret)
-			goto err;
+			goto err_upon_unmappable;
 	}
 
 	if (mappable_end < ggtt->mappable_end) {
@@ -239,14 +252,19 @@ int intel_vgt_balloon(struct drm_i915_private *dev_priv)
 					mappable_end, ggtt->mappable_end);
 
 		if (ret)
-			goto err;
+			goto err_below_mappable;
 	}
 
 	DRM_INFO("VGT balloon successfully\n");
 	return 0;
 
+err_below_mappable:
+	vgt_deballoon_space(ggtt, &bl_info.space[0]);
+err_upon_unmappable:
+	vgt_deballoon_space(ggtt, &bl_info.space[3]);
+err_upon_mappable:
+	vgt_deballoon_space(ggtt, &bl_info.space[2]);
 err:
 	DRM_ERROR("VGT balloon fail\n");
-	intel_vgt_deballoon(dev_priv);
 	return ret;
 }