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authorChris Wilson <chris@chris-wilson.co.uk>2013-04-04 21:31:03 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-05-11 13:54:01 -0700
commitb578b3a82d830e2170d403b1fb29b649e26a48fb (patch)
tree2d692c72bc3b25268c8b34347a04efb15d510bd1
parent1501dd0e01575bda28dccc92a1b260abf3d29038 (diff)
drm/i915: Workaround incoherence between fences and LLC across multiple CPUs
commit 25ff1195f8a0b3724541ae7bbe331b4296de9c06 upstream. 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 manually flush writes to memory prior to writing the fence register in conjunction with the memory barriers placed around the register write. 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. v5: Reduce to a per-cpu wbinvd() call prior to updating the fences. v6: Rewrite comments to ellide forgotten history. 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> Tested-by: Jon Bloomfield <jon.bloomfield@intel.com> (v2) Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/gpu/drm/i915/i915_gem.c28
1 files changed, 23 insertions, 5 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index de45b60516e6..3b9d18b9e92e 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2662,17 +2662,35 @@ static inline int fence_number(struct drm_i915_private *dev_priv,
return fence - dev_priv->fence_regs;
}
+static void i915_gem_write_fence__ipi(void *data)
+{
+ wbinvd();
+}
+
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 drm_device *dev = obj->base.dev;
+ struct drm_i915_private *dev_priv = dev->dev_private;
+ int fence_reg = fence_number(dev_priv, fence);
+
+ /* 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+. In theory, the write to the fence register
+ * flushes all memory transactions before, and coupled with the
+ * mb() placed around the register write we serialise all memory
+ * operations with respect to the changes in the tiler. Yet, on
+ * SNB+ we need to take a step further and emit an explicit wbinvd()
+ * on each processor in order to manually flush all memory
+ * transactions before updating the fence register.
+ */
+ if (HAS_LLC(obj->base.dev))
+ on_each_cpu(i915_gem_write_fence__ipi, NULL, 1);
+ i915_gem_write_fence(dev, fence_reg, enable ? obj : NULL);
if (enable) {
- obj->fence_reg = reg;
+ obj->fence_reg = fence_reg;
fence->obj = obj;
list_move_tail(&fence->lru_list, &dev_priv->mm.fence_list);
} else {