On Fri, Jul 18, 2025 at 11:37:36PM -0500, Jeremy Linton wrote:

+/*
+ * Unlike put_user_gcs() above, the use of copy_from_user() may provide
+ * an opening for non GCS pages to be used to source data. Therefore this
+ * should only be used in contexts where that is acceptable.
+ */

Even in user space, the GCS pages can be read with normal loads, so
already usable as a data source if one wants to (not that it's of much
use). So not sure the comment here is needed.

+static inline u64 load_user_gcs(unsigned long __user *addr, int *err)

Nitpick: name this get_user_gcs() for symmetry with put_user_gcs().

+{
+	unsigned long ret;
+	u64 load = 0;
+
+	gcsb_dsync();

Might be worth a comment here, see the one in gcs_restore_signal().

+	ret = copy_from_user(&load, addr, sizeof(load));
+	if (ret != 0)
+		*err = ret;
+	return load;
+}

Otherwise the patch looks fine:

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>