add warnings for two experimental features: Google Cloud KMS and IMPO…

…RT INTO SELECT (#16806)

encryption-at-rest.md

@@ -94,6 +94,10 @@ If encryption is enabled (that is, the value of `data-encryption-method` is not
 
 TiKV supports KMS encryption for three platforms: AWS, Google Cloud, and Azure. Depending on the platform where your service is deployed, you can choose one of them to configure KMS encryption.
 
+> **Warning:**
+>
+> Currently, specifying a master key using Google Cloud KMS is experimental. It is not recommended that you use it in production environments. This feature might be changed or removed without prior notice. If you find a bug, you can report an [issue](https://github.com/pingcap/tidb/issues) on GitHub.
+
 <SimpleTab>
 
 <div label="AWS KMS">

sql-statements/sql-statement-import-into.md

@@ -10,6 +10,10 @@ The `IMPORT INTO` statement lets you import data to TiDB via the [Physical Impor
 - `IMPORT INTO ... FROM FILE`: imports data files in formats such as `CSV`, `SQL`, and `PARQUET` into an empty table in TiDB.
 - `IMPORT INTO ... FROM SELECT`: imports the query result of a `SELECT` statement into an empty table in TiDB. You can also use it to import historical data queried with [`AS OF TIMESTAMP`](/as-of-timestamp.md).
 
+> **Warning:**
+>
+> Currently, `IMPORT INTO ... FROM SELECT` is experimental. It is not recommended that you use it in production environments. This feature might be changed or removed without prior notice. If you find a bug, you can report an [issue](https://github.com/pingcap/tidb/issues) on GitHub.
+
 ## Restrictions
 
 - `IMPORT INTO` only supports importing data into existing empty tables in the database.