[Intel-gfx] [PATCH] drm/i915: Disable stolen memory when DMAR is active

[Chris Wilson]

We have reports of heavy screen corruption if we try to use the stolen
memory reserved by the BIOS whilst the DMA-Remapper is active. This
quirk may be only specific to a few machines or BIOSes, but first lets
apply the big hammer and always disable use of stolen memory when DMAR
is active.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=68535
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_gem_stolen.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
index 984ada1b0084..13a849afe479 100644
--- a/drivers/gpu/drm/i915/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
@@ -325,11 +325,25 @@ void i915_gem_cleanup_stolen(struct drm_device *dev)
 	drm_mm_takedown(&dev_priv->mm.stolen);
 }
 
+static bool need_dmar_wa(struct drm_device *dev)
+{
+#ifdef CONFIG_INTEL_IOMMU
+	if (INTEL_INFO(dev)->gen >= 6 && intel_iommu_gfx_mapped)
+		return true;
+#endif
+	return false;
+}
+
 int i915_gem_init_stolen(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct resource *r;
 
+	if (need_dmar_wa(dev)) {
+		DRM_INFO("DMAR active, disabling use of stolen memory\n");
+		return 0;
+	}
+
 	if (dev_priv->gtt.stolen_size == 0)
 		return 0;
 
-- 
1.9.0