[Intel-gfx] [PATCH 1/2] drm/i915: Fix NPD in PMU during driver teardown

[Stuart Summers]

In the driver teardown, we are unregistering the gt prior
to unregistering the PMU. This means there is a small window
of time in which the application can request metrics from the
PMU, some of which are calling into the uapi engines list,
while the engines are not available. In this case we can
see null pointer dereferences.

Fix this ordering in both the driver load and unload sequences.

v1: Actually address the driver load/unload ordering issue
v2: Remove the NULL checks since they shouldn't be necessary
    now with the proper ordering

Fixes: 42014f69bb235 ("drm/i915: Hook up GT power management")
Signed-off-by: Stuart Summers <stuart.summers at intel.com>
---
 drivers/gpu/drm/i915/i915_driver.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_driver.c b/drivers/gpu/drm/i915/i915_driver.c
index deb8a8b76965a..ee4dcb85d2060 100644
--- a/drivers/gpu/drm/i915/i915_driver.c
+++ b/drivers/gpu/drm/i915/i915_driver.c
@@ -717,7 +717,6 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
 	struct drm_device *dev = &dev_priv->drm;
 
 	i915_gem_driver_register(dev_priv);
-	i915_pmu_register(dev_priv);
 
 	intel_vgpu_register(dev_priv);
 
@@ -731,11 +730,12 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
 	i915_debugfs_register(dev_priv);
 	i915_setup_sysfs(dev_priv);
 
+	intel_gt_driver_register(to_gt(dev_priv));
+
 	/* Depends on sysfs having been initialized */
+	i915_pmu_register(dev_priv);
 	i915_perf_register(dev_priv);
 
-	intel_gt_driver_register(to_gt(dev_priv));
-
 	intel_display_driver_register(dev_priv);
 
 	intel_power_domains_enable(dev_priv);
@@ -762,11 +762,12 @@ static void i915_driver_unregister(struct drm_i915_private *dev_priv)
 
 	intel_display_driver_unregister(dev_priv);
 
-	intel_gt_driver_unregister(to_gt(dev_priv));
-
 	i915_perf_unregister(dev_priv);
+	/* GT should be available until PMU is gone */
 	i915_pmu_unregister(dev_priv);
 
+	intel_gt_driver_unregister(to_gt(dev_priv));
+
 	i915_teardown_sysfs(dev_priv);
 	drm_dev_unplug(&dev_priv->drm);
 
-- 
2.25.1