drm/i915: Prevent user context creation while wedged

Introduce a new ABI method for detecting a wedged driver by reporting
-EIO from DRM_IOCTL_I915_GEM_CONTEXT_CREATE.

This came up in considering how to handle context recovery from
userspace. There we wish to create a new context after the original is
banned (the clients opts into the no recovery after reset strategy) in
order to rebuild the mesa context from scratch. In doing so, if the
device was wedged and not the context banned, we would fall into a loop
of permanently trying to recreate the context and never making forward
progress. This patch would inform the client that we are no longer able
to create a context, and the client would have no choice but to abort
(or at least inform its callers about the lost device for anv).

References: https://lists.freedesktop.org/archives/mesa-dev/2019-February/215469.htmlSigned-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190220225556.28715-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_context.c

@@ -802,18 +802,22 @@ static bool client_is_banned(struct drm_i915_file_private *file_priv)
 int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
 				  struct drm_file *file)
 {
-	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct drm_i915_private *i915 = to_i915(dev);
 	struct drm_i915_gem_context_create *args = data;
 	struct drm_i915_file_private *file_priv = file->driver_priv;
 	struct i915_gem_context *ctx;
 	int ret;
 
-	if (!DRIVER_CAPS(dev_priv)->has_logical_contexts)
+	if (!DRIVER_CAPS(i915)->has_logical_contexts)
 		return -ENODEV;
 
 	if (args->pad != 0)
 		return -EINVAL;
 
+	ret = i915_terminally_wedged(i915);
+	if (ret)
+		return ret;
+
 	if (client_is_banned(file_priv)) {
 		DRM_DEBUG("client %s[%d] banned from creating ctx\n",
 			  current->comm,
@@ -826,7 +830,7 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
 	if (ret)
 		return ret;
 
-	ctx = i915_gem_create_context(dev_priv, file_priv);
+	ctx = i915_gem_create_context(i915, file_priv);
 	mutex_unlock(&dev->struct_mutex);
 	if (IS_ERR(ctx))
 		return PTR_ERR(ctx);