@@ -2689,17 +2689,51 @@ static inline int fence_number(struct drm_i915_private *dev_priv,
return fence - dev_priv->fence_regs;
}
+struct write_fence {
+ struct drm_device *dev;
+ struct drm_i915_gem_object *obj;
+ int fence;
+};
+
+static void i915_gem_write_fence__ipi(void *data)
+{
+ struct write_fence *args = data;
+
+ wbinvd();
+
+ i915_gem_write_fence(args->dev, args->fence, args->obj);
+}
+
static void i915_gem_object_update_fence(struct drm_i915_gem_object *obj,
struct drm_i915_fence_reg *fence,
bool enable)
{
struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
- int reg = fence_number(dev_priv, fence);
-
- i915_gem_write_fence(obj->base.dev, reg, enable ? obj : NULL);
+ struct write_fence args = {
+ .dev = obj->base.dev,
+ .fence = fence_number(dev_priv, fence),
+ .obj = enable ? obj : NULL,
+ };
+
+ /* In order to fully serialize access to the fenced region and
+ * the update to the fence register we need to take extreme
+ * measures on SNB+, and write the fence from each cpu taking
+ * care to serialise memory accesses on each. The usual mb(),
+ * or even a mb() on each CPU is not enough to ensure that access
+ * to the fenced region is coherent across the change in fence
+ * register.
+ *
+ * As it turns out for IVB, I need slightly heavier bullets and
+ * need to do a wbinvd() per-processor to serialise memory acceses
+ * with the fence update.
+ */
+ if (HAS_LLC(obj->base.dev))
+ on_each_cpu(i915_gem_write_fence__ipi, &args, 1);
+ else
+ i915_gem_write_fence(args.dev, args.fence, args.obj);
if (enable) {
- obj->fence_reg = reg;
+ obj->fence_reg = args.fence;
fence->obj = obj;
list_move_tail(&fence->lru_list, &dev_priv->mm.fence_list);
} else {
In order to fully serialize access to the fenced region and the update to the fence register we need to take extreme measures on SNB+, and write the fence from each cpu taking care to serialise memory accesses on each. The usual mb(), or even a mb() on each CPU is not enough to ensure that access to the fenced region is coherent across the change in fence register. Fixes i-g-t/gem_fence_thrash v2: Bring a bigger gun v3: Switch the bigger gun for heavier bullets (Arjan van de Ven) v4: Remove changes for working generations. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=62191 Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> CC: Jon Bloomfield <jon.bloomfield@intel.com> Cc: stable@vger.kernel.org --- drivers/gpu/drm/i915/i915_gem.c | 42 +++++++++++++++++++++++++++++++++++---- 1 file changed, 38 insertions(+), 4 deletions(-)