[Intel-gfx] [PATCH] drm/i915: Unpin last_context at reset

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

We're forgetting to unpin the last_context from the ggtt at GPU reset
time. This leads to the vma pin_count leaking at every reset if the
last context wasn't the ring default context. Further use of the same
context will trigger the pin_count check in i915_gem_object_pin() and
userspace will be faced with EBUSY as a result.

This plaques kms_flip rather badly since it performs lots of resets,
and every fd has its own default context these days.

Fix the problem by properly unpinning the last context at reset.

Testcase: igt/gem_ctx_exec/reset-pin-leak
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 3ffe308..e362c96 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -382,6 +382,9 @@ void i915_gem_context_reset(struct drm_device *dev)
 			dctx->obj->active = 0;
 		}
 
+		if (ring->last_context->obj && i == RCS)
+			i915_gem_object_ggtt_unpin(ring->last_context->obj);
+
 		i915_gem_context_unreference(ring->last_context);
 		i915_gem_context_reference(dctx);
 		ring->last_context = dctx;
-- 
1.8.5.5