[PATCH v6 04/18] fs/resctrl: Introduce kernel mode enum

[Babu Moger]

Kernel mode work can use different allocation and monitoring associations
than the originating user task. On x86, Privilege Level Zero Association
(PLZA) enables the kernel to switch to a different CLOSID and/or RMID when
entering kernel mode.

Architectures need a common way to name kernel modes before resctrl
can report what is active or what the platform supports.

Introduce enum resctrl_kernel_mode:
  - RESCTRL_INHERIT_USER: Kernel mode work inherits allocation and
    monitoring from the user task.
  - RESCTRL_GLOBAL_ENABLE_PER_CPU: Kernel mode work uses allocation and/or
    monitoring associations that differ from the user task.

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v6: changelog update and code comment update.
    Renamed RESCTRL_ASSIGN_GLOBAL_ENABLE_PER_CPU to RESCTRL_GLOBAL_ENABLE_PER_CPU.

v5: Collapse the two global-assign modes into a single
    RESCTRL_ASSIGN_GLOBAL_ENABLE_PER_CPU value. Update the changelog to
    match the enum names and descriptions in the code.

v4: Updated the changelog to be generic as possible.
    Moved the enum resctrl_kernel_mode to include/linux/resctrl.h.
    Updated the code comments to be generic.
    Removed resctrl_kmode_cfg from the code. This definition can be fs
    specific only and architectures dont need to know.
    Changed enum name to resctrl_kernel_mode from resctrl_kernel_modes.

v3: Removed resctrl_kmode definition.
    Changed the kernel mode definitions to enum resctrl_kernel_modes.
    Used BIT() to set/test the features.
    Added details to changelog.

v2: New patch to handle PLZA interfaces with /sys/fs/resctrl/info/ directory.
    https://lore.kernel.org/lkml/2ab556af-095b-422b-9396-f845c6fd0342@xxxxxxxxx/
---
 include/linux/resctrl.h | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 10dfdca7f4bf..f6adff7f4e1f 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -723,6 +723,35 @@ int resctrl_arch_io_alloc_enable(struct rdt_resource *r, bool enable);
  */
 bool resctrl_arch_get_io_alloc_enabled(struct rdt_resource *r);
 
+/**
+ * enum resctrl_kernel_mode - Kernel mode control and monitoring association.
+ *
+ * @RESCTRL_INHERIT_USER:
+ *     Kernel mode inherits both allocation and monitoring associations
+ *     from the user-space task. On x86, the kernel uses the same CLOSID and
+ *     RMID as the user-space task.
+ *
+ * @RESCTRL_GLOBAL_ENABLE_PER_CPU:
+ *     All kernel mode work uses the same allocation and/or monitoring
+ *     association via an assigned CTRL_MON or MON group. The mode can
+ *     be enabled/disabled per-CPU. When the mode is disabled on a CPU
+ *     then the kernel work on that CPU inherits the allocation and
+ *     monitoring association from the user-space task, effectively the
+ *     kernel mode becomes RESCTRL_INHERIT_USER on that CPU.
+ *
+ *     All online CPUs are included by default. A subset may be selected
+ *     through the resctrl group interface, and a CTRL_MON or MON group
+ *     may be assigned to this mode. On x86, CLOSID and RMID are configured
+ *     independently; either or both may differ from the user-space task.
+ */
+enum resctrl_kernel_mode {
+	RESCTRL_INHERIT_USER,
+	RESCTRL_GLOBAL_ENABLE_PER_CPU,
+	RESCTRL_KMODE_LAST = RESCTRL_GLOBAL_ENABLE_PER_CPU
+};
+
+#define RESCTRL_NUM_KERNEL_MODES (RESCTRL_KMODE_LAST + 1)
+
 extern unsigned int resctrl_rmid_realloc_threshold;
 extern unsigned int resctrl_rmid_realloc_limit;
 
-- 
2.43.0