From 19656430a874132a1d79c56387a6eec1ef9a5689 Mon Sep 17 00:00:00 2001 From: Oscar Mateo Date: Fri, 16 May 2014 14:20:43 +0100 Subject: [PATCH] drm/i915: Gracefully handle obj not bound to GGTT in is_pin_display Otherwise, we do a NULL pointer dereference. I've seen this happen while handling an error in i915_gem_object_pin_to_display_plane(): If i915_gem_object_set_cache_level() fails, we call is_pin_display() to handle the error. At this point, the object is still not pinned to GGTT and maybe not even bound, so we have to check before we dereference its GGTT vma. The IGT kms_flip/bo-too-big tests for this bug. v2: Chris Wilson says restoring the old value is easier, but that is_pin_display is useful as a theory of operation. Take the solomonic decision: at least this way is_pin_display is a little more robust (until Chris can kill it off). v3: Chris suggests the WARN in i915_gem_obj_to_ggtt has outlived its usefulness: add a reminder to remove it. Issue: VIZ-3772 Signed-off-by: Oscar Mateo Testcase: igt/kms_flip/bo-too-big Reviewed-by: Chris Wilson Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/i915_gem.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 034ba2c6064a..f6c03513de52 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -3641,6 +3641,15 @@ unlock: static bool is_pin_display(struct drm_i915_gem_object *obj) { + struct i915_vma *vma; + + if (list_empty(&obj->vma_list)) + return false; + + vma = i915_gem_obj_to_ggtt(obj); + if (!vma) + return false; + /* There are 3 sources that pin objects: * 1. The display engine (scanouts, sprites, cursors); * 2. Reservations for execbuffer; @@ -3652,7 +3661,7 @@ static bool is_pin_display(struct drm_i915_gem_object *obj) * subtracting the potential reference by the user, any pin_count * remains, it must be due to another use by the display engine. */ - return i915_gem_obj_to_ggtt(obj)->pin_count - !!obj->user_pin_count; + return vma->pin_count - !!obj->user_pin_count; } /* @@ -3666,6 +3675,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj, struct intel_ring_buffer *pipelined) { u32 old_read_domains, old_write_domain; + bool was_pin_display; int ret; if (pipelined != obj->ring) { @@ -3677,6 +3687,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj, /* Mark the pin_display early so that we account for the * display coherency whilst setting up the cache domains. */ + was_pin_display = obj->pin_display; obj->pin_display = true; /* The display engine is not coherent with the LLC cache on gen6. As @@ -3719,7 +3730,8 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj, return 0; err_unpin_display: - obj->pin_display = is_pin_display(obj); + WARN_ON(was_pin_display != is_pin_display(obj)); + obj->pin_display = was_pin_display; return ret; } @@ -5115,6 +5127,9 @@ struct i915_vma *i915_gem_obj_to_ggtt(struct drm_i915_gem_object *obj) { struct i915_vma *vma; + /* This WARN has probably outlived its usefulness (callers already + * WARN if they don't find the GGTT vma they expect). When removing, + * remember to remove the pre-check in is_pin_display() as well */ if (WARN_ON(list_empty(&obj->vma_list))) return NULL; -- 2.20.1