drm/i915: Report IOMMU enabled status for GPU hangs

The IOMMU for Intel graphics has historically had many issues resulting
in random GPU hangs. Lets include its status when capturing the GPU hang
error state for post-mortem analysis.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -484,6 +484,7 @@ struct drm_i915_error_state {
 	struct timeval time;
 
 	char error_msg[128];
+	int iommu;
 	u32 reset_count;
 	u32 suspend_count;
 

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -369,6 +369,7 @@ int i915_error_state_to_str(struct drm_i915_error_state_buf *m,
 	err_printf(m, "Reset count: %u\n", error->reset_count);
 	err_printf(m, "Suspend count: %u\n", error->suspend_count);
 	err_printf(m, "PCI ID: 0x%04x\n", dev->pdev->device);
+	err_printf(m, "IOMMU enabled?: %d\n", error->iommu);
 	err_printf(m, "EIR: 0x%08x\n", error->eir);
 	err_printf(m, "IER: 0x%08x\n", error->ier);
 	if (INTEL_INFO(dev)->gen >= 8) {
@@ -1266,6 +1267,10 @@ static void i915_error_capture_msg(struct drm_device *dev,
 static void i915_capture_gen_state(struct drm_i915_private *dev_priv,
 				   struct drm_i915_error_state *error)
 {
+	error->iommu = -1;
+#ifdef CONFIG_INTEL_IOMMU
+	error->iommu = intel_iommu_gfx_mapped;
+#endif
 	error->reset_count = i915_reset_count(&dev_priv->gpu_error);
 	error->suspend_count = dev_priv->suspend_count;
 }