[Intel-gfx] [PATCH 48/66] drm/i915: Better reset handling for contexts

[Ben Widawsky]

This patch adds to changes for contexts on reset:
Sets last context to default - this will prevent the context switch
happening after a reset. That switch is not possible because the
rings are hung during reset and context switch requires reset. This
behavior will need to be reworked in the future, but this is what we
want for now.

In the future, we'll also want to reset the guilty context to
uninitialized. We should wait for ARB_Robustness related code to land
for that.

This is somewhat for paranoia.  Because we really don't know what the
GPU was doing when it hung, or the state it was in (mid context write,
for example), later restoring the context is a bad idea. By setting the
flag to not initialized, the next load of that context will not restore
the state, and thus on the subsequent switch away from the context will
overwrite the old data.

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_drv.h         |  1 +
 drivers/gpu/drm/i915/i915_gem.c         |  2 ++
 drivers/gpu/drm/i915/i915_gem_context.c | 54 +++++++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 19ae0dc..5beba7a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1890,6 +1890,7 @@ i915_gem_ggtt_pin(struct drm_i915_gem_object *obj,
 /* i915_gem_context.c */
 void i915_gem_context_init(struct drm_device *dev);
 void i915_gem_context_fini(struct drm_device *dev);
+void i915_gem_context_reset(struct drm_device *dev);
 int i915_gem_context_enable(struct drm_i915_private *dev_priv);
 int i915_gem_context_open(struct drm_device *dev, struct drm_file *file);
 void i915_gem_context_close(struct drm_device *dev, struct drm_file *file);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9abc3c8..d440dd5 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2323,6 +2323,8 @@ bool i915_gem_reset(struct drm_device *dev)
 
 	i915_gem_cleanup_ringbuffer(dev);
 
+	i915_gem_context_reset(dev);
+
 	/* Move everything out of the GPU domains to ensure we do any
 	 * necessary invalidation upon reuse.
 	 */
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 3e0413e..e585e5a 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -245,6 +245,60 @@ err_destroy:
 	return ret;
 }
 
+static int context_reset(int id, void *p, void *data)
+{
+#if 0
+	struct i915_hw_context *ctx = p;
+	ctx->is_initialized = false;
+#endif
+	return 0;
+}
+
+void i915_gem_context_reset(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	struct intel_ring_buffer *ring;
+	struct drm_file *file;
+	int i;
+
+	if (dev_priv->hw_contexts_disabled)
+		return;
+
+	/* Prevent the hardware from restoring the last context (which hung) on
+	 * the next switch */
+	for (i = 0; i < I915_NUM_RINGS; i++) {
+		struct i915_hw_context *dctx;
+		if (!(INTEL_INFO(dev)->ring_mask & (1<<i)))
+			continue;
+
+		/* Do a fake switch to the default context */
+		ring = &dev_priv->ring[i];
+		dctx = ring->default_context;
+		if (WARN_ON(!dctx))
+			continue;
+
+		if (!ring->last_context)
+			continue;
+
+		if (ring->last_context == dctx)
+			continue;
+
+		if (i == RCS)
+			WARN_ON(i915_gem_ggtt_pin(dctx->obj, CONTEXT_ALIGN,
+						  false, false));
+
+		i915_gem_context_unreference(ring->last_context);
+		i915_gem_context_reference(dctx);
+		ring->last_context = dctx;
+	}
+
+
+	list_for_each_entry(file, &dev->filelist, lhead) {
+		struct drm_i915_file_private *file_priv = file->driver_priv;
+		idr_for_each(&file_priv->context_idr, context_reset, NULL);
+	}
+}
+
 void i915_gem_context_init(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-- 
1.8.3.1