1 files changed, 160 insertions, 43 deletions

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 5a1402544d48..c4f89e4b1665 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -278,6 +278,42 @@ proto_close:
 	return err;
 }
 
+static int proto_context_register_locked(struct drm_i915_file_private *fpriv,
+					 struct i915_gem_proto_context *pc,
+					 u32 *id)
+{
+	int ret;
+	void *old;
+
+	lockdep_assert_held(&fpriv->proto_context_lock);
+
+	ret = xa_alloc(&fpriv->context_xa, id, NULL, xa_limit_32b, GFP_KERNEL);
+	if (ret)
+		return ret;
+
+	old = xa_store(&fpriv->proto_context_xa, *id, pc, GFP_KERNEL);
+	if (xa_is_err(old)) {
+		xa_erase(&fpriv->context_xa, *id);
+		return xa_err(old);
+	}
+	WARN_ON(old);
+
+	return 0;
+}
+
+static int proto_context_register(struct drm_i915_file_private *fpriv,
+				  struct i915_gem_proto_context *pc,
+				  u32 *id)
+{
+	int ret;
+
+	mutex_lock(&fpriv->proto_context_lock);
+	ret = proto_context_register_locked(fpriv, pc, id);
+	mutex_unlock(&fpriv->proto_context_lock);
+
+	return ret;
+}
+
 static int set_proto_ctx_vm(struct drm_i915_file_private *fpriv,
 			    struct i915_gem_proto_context *pc,
 			    const struct drm_i915_gem_context_param *args)
@@ -1448,12 +1484,12 @@ void i915_gem_init__contexts(struct drm_i915_private *i915)
 	init_contexts(&i915->gem.contexts);
 }
 
-static int gem_context_register(struct i915_gem_context *ctx,
-				struct drm_i915_file_private *fpriv,
-				u32 *id)
+static void gem_context_register(struct i915_gem_context *ctx,
+				 struct drm_i915_file_private *fpriv,
+				 u32 id)
 {
 	struct drm_i915_private *i915 = ctx->i915;
-	int ret;
+	void *old;
 
 	ctx->file_priv = fpriv;
 
@@ -1462,19 +1498,12 @@ static int gem_context_register(struct i915_gem_context *ctx,
 		 current->comm, pid_nr(ctx->pid));
 
 	/* And finally expose ourselves to userspace via the idr */
-	ret = xa_alloc(&fpriv->context_xa, id, ctx, xa_limit_32b, GFP_KERNEL);
-	if (ret)
-		goto err_pid;
+	old = xa_store(&fpriv->context_xa, id, ctx, GFP_KERNEL);
+	WARN_ON(old);
 
 	spin_lock(&i915->gem.contexts.lock);
 	list_add_tail(&ctx->link, &i915->gem.contexts.list);
 	spin_unlock(&i915->gem.contexts.lock);
-
-	return 0;
-
-err_pid:
-	put_pid(fetch_and_zero(&ctx->pid));
-	return ret;
 }
 
 int i915_gem_context_open(struct drm_i915_private *i915,
@@ -1484,9 +1513,12 @@ int i915_gem_context_open(struct drm_i915_private *i915,
 	struct i915_gem_proto_context *pc;
 	struct i915_gem_context *ctx;
 	int err;
-	u32 id;
 
-	xa_init_flags(&file_priv->context_xa, XA_FLAGS_ALLOC);
+	mutex_init(&file_priv->proto_context_lock);
+	xa_init_flags(&file_priv->proto_context_xa, XA_FLAGS_ALLOC);
+
+	/* 0 reserved for the default context */
+	xa_init_flags(&file_priv->context_xa, XA_FLAGS_ALLOC1);
 
 	/* 0 reserved for invalid/unassigned ppgtt */
 	xa_init_flags(&file_priv->vm_xa, XA_FLAGS_ALLOC1);
@@ -1504,28 +1536,31 @@ int i915_gem_context_open(struct drm_i915_private *i915,
 		goto err;
 	}
 
-	err = gem_context_register(ctx, file_priv, &id);
-	if (err < 0)
-		goto err_ctx;
+	gem_context_register(ctx, file_priv, 0);
 
-	GEM_BUG_ON(id);
 	return 0;
 
-err_ctx:
-	context_close(ctx);
 err:
 	xa_destroy(&file_priv->vm_xa);
 	xa_destroy(&file_priv->context_xa);
+	xa_destroy(&file_priv->proto_context_xa);
+	mutex_destroy(&file_priv->proto_context_lock);
 	return err;
 }
 
 void i915_gem_context_close(struct drm_file *file)
 {
 	struct drm_i915_file_private *file_priv = file->driver_priv;
+	struct i915_gem_proto_context *pc;
 	struct i915_address_space *vm;
 	struct i915_gem_context *ctx;
 	unsigned long idx;
 
+	xa_for_each(&file_priv->proto_context_xa, idx, pc)
+		proto_context_close(pc);
+	xa_destroy(&file_priv->proto_context_xa);
+	mutex_destroy(&file_priv->proto_context_lock);
+
 	xa_for_each(&file_priv->context_xa, idx, ctx)
 		context_close(ctx);
 	xa_destroy(&file_priv->context_xa);
@@ -2480,12 +2515,73 @@ static bool client_is_banned(struct drm_i915_file_private *file_priv)
 	return atomic_read(&file_priv->ban_score) >= I915_CLIENT_SCORE_BANNED;
 }
 
+static inline struct i915_gem_context *
+__context_lookup(struct drm_i915_file_private *file_priv, u32 id)
+{
+	struct i915_gem_context *ctx;
+
+	rcu_read_lock();
+	ctx = xa_load(&file_priv->context_xa, id);
+	if (ctx && !kref_get_unless_zero(&ctx->ref))
+		ctx = NULL;
+	rcu_read_unlock();
+
+	return ctx;
+}
+
+static struct i915_gem_context *
+finalize_create_context_locked(struct drm_i915_file_private *file_priv,
+			       struct i915_gem_proto_context *pc, u32 id)
+{
+	struct i915_gem_context *ctx;
+	void *old;
+
+	lockdep_assert_held(&file_priv->proto_context_lock);
+
+	ctx = i915_gem_create_context(file_priv->dev_priv, pc);
+	if (IS_ERR(ctx))
+		return ctx;
+
+	gem_context_register(ctx, file_priv, id);
+
+	old = xa_erase(&file_priv->proto_context_xa, id);
+	GEM_BUG_ON(old != pc);
+	proto_context_close(pc);
+
+	/* One for the xarray and one for the caller */
+	return i915_gem_context_get(ctx);
+}
+
+struct i915_gem_context *
+i915_gem_context_lookup(struct drm_i915_file_private *file_priv, u32 id)
+{
+	struct i915_gem_proto_context *pc;
+	struct i915_gem_context *ctx;
+
+	ctx = __context_lookup(file_priv, id);
+	if (ctx)
+		return ctx;
+
+	mutex_lock(&file_priv->proto_context_lock);
+	/* Try one more time under the lock */
+	ctx = __context_lookup(file_priv, id);
+	if (!ctx) {
+		pc = xa_load(&file_priv->proto_context_xa, id);
+		if (!pc)
+			ctx = ERR_PTR(-ENOENT);
+		else
+			ctx = finalize_create_context_locked(file_priv, pc, id);
+	}
+	mutex_unlock(&file_priv->proto_context_lock);
+
+	return ctx;
+}
+
 int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
 				  struct drm_file *file)
 {
 	struct drm_i915_private *i915 = to_i915(dev);
 	struct drm_i915_gem_context_create_ext *args = data;
-	struct i915_gem_context *ctx;
 	struct create_ext ext_data;
 	int ret;
 	u32 id;
@@ -2517,28 +2613,21 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
 					   create_extensions,
 					   ARRAY_SIZE(create_extensions),
 					   &ext_data);
-		if (ret) {
-			proto_context_close(ext_data.pc);
-			return ret;
-		}
+		if (ret)
+			goto err_pc;
 	}
 
-	ctx = i915_gem_create_context(i915, ext_data.pc);
-	proto_context_close(ext_data.pc);
-	if (IS_ERR(ctx))
-		return PTR_ERR(ctx);
-
-	ret = gem_context_register(ctx, ext_data.fpriv, &id);
+	ret = proto_context_register(ext_data.fpriv, ext_data.pc, &id);
 	if (ret < 0)
-		goto err_ctx;
+		goto err_pc;
 
 	args->ctx_id = id;
 	drm_dbg(&i915->drm, "HW context %d created\n", args->ctx_id);
 
 	return 0;
 
-err_ctx:
-	context_close(ctx);
+err_pc:
+	proto_context_close(ext_data.pc);
 	return ret;
 }
 
@@ -2547,6 +2636,7 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
 {
 	struct drm_i915_gem_context_destroy *args = data;
 	struct drm_i915_file_private *file_priv = file->driver_priv;
+	struct i915_gem_proto_context *pc;
 	struct i915_gem_context *ctx;
 
 	if (args->pad != 0)
@@ -2555,11 +2645,24 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
 	if (!args->ctx_id)
 		return -ENOENT;
 
+	/* We need to hold the proto-context lock here to prevent races
+	 * with finalize_create_context_locked().
+	 */
+	mutex_lock(&file_priv->proto_context_lock);
 	ctx = xa_erase(&file_priv->context_xa, args->ctx_id);
-	if (!ctx)
+	pc = xa_erase(&file_priv->proto_context_xa, args->ctx_id);
+	mutex_unlock(&file_priv->proto_context_lock);
+
+	if (!ctx && !pc)
 		return -ENOENT;
+	GEM_WARN_ON(ctx && pc);
+
+	if (pc)
+		proto_context_close(pc);
+
+	if (ctx)
+		context_close(ctx);
 
-	context_close(ctx);
 	return 0;
 }
 
@@ -2692,16 +2795,30 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
 {
 	struct drm_i915_file_private *file_priv = file->driver_priv;
 	struct drm_i915_gem_context_param *args = data;
+	struct i915_gem_proto_context *pc;
 	struct i915_gem_context *ctx;
-	int ret;
+	int ret = 0;
 
-	ctx = i915_gem_context_lookup(file_priv, args->ctx_id);
-	if (IS_ERR(ctx))
-		return PTR_ERR(ctx);
+	mutex_lock(&file_priv->proto_context_lock);
+	ctx = __context_lookup(file_priv, args->ctx_id);
+	if (!ctx) {
+		/* FIXME: We should consider disallowing SET_CONTEXT_PARAM
+		 * for most things on future platforms.  Clients should be
+		 * using CONTEXT_CREATE_EXT_PARAM instead.
+		 */
+		pc = xa_load(&file_priv->proto_context_xa, args->ctx_id);
+		if (pc)
+			ret = set_proto_ctx_param(file_priv, pc, args);
+		else
+			ret = -ENOENT;
+	}
+	mutex_unlock(&file_priv->proto_context_lock);
 
-	ret = ctx_setparam(file_priv, ctx, args);
+	if (ctx) {
+		ret = ctx_setparam(file_priv, ctx, args);
+		i915_gem_context_put(ctx);
+	}
 
-	i915_gem_context_put(ctx);
 	return ret;
 }