Remove that entry from the resctrl_schema_all list when driver
is loaded. Put it back again when driver is unloaded.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 include/linux/resctrl.h                |  4 ++++
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 19 +++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 691805214f41..246644f53bde 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -223,6 +223,8 @@ struct resctrl_fileinfo {
  * @rmdir:	Callback when a resctrl directory is removed.
  * @ctrlfiles:	Array of files to create in ctrlmon directories.
  * @schema:	Driver supplied to manage a line in schemata file.
+ * @schema_override: Name of resource in schemata to override.
+ * @save_schema: List to save overridden schema while driver loaded
  */
 struct resctrl_driver {
 	struct list_head	list;
@@ -232,6 +234,8 @@ struct resctrl_driver {
 	int			(*rmdir)(int oclos, int ormid, int nclos, int nrmid);
 	struct resctrl_fileinfo	*ctrlfiles;
 	struct resctrl_schema	schema;
+	char			*schema_override;
+	struct list_head	save_schema;
 };
 
 int resctrl_register_driver(struct resctrl_driver *d);
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index cc2292a7435b..4fc12ad56843 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2547,6 +2547,19 @@ static void rdtgroup_update_ctrl_dir(struct resctrl_fileinfo *files, bool add)
 	}
 }
 
+static void driver_override(struct resctrl_driver *d)
+{
+	struct resctrl_schema *rs;
+
+	list_for_each_entry(rs, &resctrl_schema_all, list) {
+		if (strncmp(d->schema_override, rs->name, sizeof(rs->name)))
+			continue;
+		INIT_LIST_HEAD(&d->save_schema);
+		list_move(&rs->list, &d->save_schema);
+		break;
+	}
+}
+
 static void driver_up(struct resctrl_driver *d)
 {
 	if (d->mount)
@@ -2575,6 +2588,9 @@ int resctrl_register_driver(struct resctrl_driver *d)
 	if (d->schema.name[0])
 		list_add(&d->schema.list, &resctrl_schema_all);
 
+	if (d->schema_override)
+		driver_override(d);
+
 	if (resctrl_is_mounted)
 		driver_up(d);
 	mutex_unlock(&rdtgroup_mutex);
@@ -2592,6 +2608,9 @@ void resctrl_unregister_driver(struct resctrl_driver *d)
 	if (d->schema.name[0])
 		list_del(&d->schema.list);
 
+	if (d->schema_override && !list_empty(&d->save_schema))
+		list_move(d->save_schema.next, &resctrl_schema_all);
+
 	if (resctrl_is_mounted)
 		driver_down(d);
 	mutex_unlock(&rdtgroup_mutex);
-- 
2.39.2

Hi Tony,

On 4/20/2023 3:06 PM, Tony Luck wrote:
> Remove that entry from the resctrl_schema_all list when driver
> is loaded. Put it back again when driver is unloaded.

This is unexpected. It sounds like the system would advertise
a supported resource with appropriate properties but for some reason this
is not correct, optional in some way, or perhaps resources are 
conflicting? Where would it be decided whether the overriding driver
should be loaded and why can that logic not be in enumeration
within resctrl?

Reinette