[Intel-gfx] [PATCH] drm/i915: Fix GVT balloon fail path handling

[Zhenyu Wang]

For any reason if GVT balloon failed, deballoon would be called.
This adds a simple mask to check validity of balloon spaces. When
failure happens, that mask is used to track for deballoon, so it
won't cause any invalid space reference in fail path, which fixed
kernel oops when balloon error happened.

Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_vgpu.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_vgpu.c b/drivers/gpu/drm/i915/i915_vgpu.c
index 94d3992b599d..5aec34db1aaa 100644
--- a/drivers/gpu/drm/i915/i915_vgpu.c
+++ b/drivers/gpu/drm/i915/i915_vgpu.c
@@ -94,6 +94,7 @@ struct _balloon_info_ {
 	 * graphic memory, 2/3 for unmappable graphic memory.
 	 */
 	struct drm_mm_node space[4];
+	u8 valid;
 };
 
 static struct _balloon_info_ bl_info;
@@ -126,8 +127,12 @@ void intel_vgt_deballoon(struct drm_i915_private *dev_priv)
 
 	DRM_DEBUG("VGT deballoon.\n");
 
-	for (i = 0; i < 4; i++)
-		vgt_deballoon_space(&dev_priv->ggtt, &bl_info.space[i]);
+	for (i = 0; i < 4; i++) {
+		if (bl_info.valid & BIT(i)) {
+			vgt_deballoon_space(&dev_priv->ggtt, &bl_info.space[i]);
+			bl_info.valid &= ~(u8)BIT(i);
+		}
+	}
 }
 
 static int vgt_balloon_space(struct i915_ggtt *ggtt,
@@ -232,16 +237,17 @@ int intel_vgt_balloon(struct drm_i915_private *dev_priv)
 	if (unmappable_base > ggtt->mappable_end) {
 		ret = vgt_balloon_space(ggtt, &bl_info.space[2],
 					ggtt->mappable_end, unmappable_base);
-
 		if (ret)
 			goto err;
+		bl_info.valid |= BIT(2);
 	}
 
 	if (unmappable_end < ggtt_end) {
 		ret = vgt_balloon_space(ggtt, &bl_info.space[3],
 					unmappable_end, ggtt_end);
 		if (ret)
-			goto err_upon_mappable;
+			goto err;
+		bl_info.valid |= BIT(3);
 	}
 
 	/* Mappable graphic memory ballooning */
@@ -250,7 +256,8 @@ int intel_vgt_balloon(struct drm_i915_private *dev_priv)
 					0, mappable_base);
 
 		if (ret)
-			goto err_upon_unmappable;
+			goto err;
+		bl_info.valid |= BIT(0);
 	}
 
 	if (mappable_end < ggtt->mappable_end) {
@@ -258,19 +265,15 @@ int intel_vgt_balloon(struct drm_i915_private *dev_priv)
 					mappable_end, ggtt->mappable_end);
 
 		if (ret)
-			goto err_below_mappable;
+			goto err;
+		bl_info.valid |= BIT(1);
 	}
 
 	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:
+	intel_vgt_deballoon(dev_priv);
 	DRM_ERROR("VGT balloon fail\n");
 	return ret;
 }
-- 
2.20.1