[PATCH v6 06/18] fs/resctrl: Introduce kernel mode states for resctrl

[Babu Moger]

The filesystem tracks supported kernel modes, the active mode, and the
control and monitoring association for the assigned group.

Introduce struct resctrl_kmode_cfg and initialize the default configuration
from the platform's capabilities.

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
v6: Drop ctrl_en/mon_en and use resctrl_arch_alloc_capable() /
    resctrl_arch_mon_capable() directly. Flatten caps/active into
    resctrl_kmode_cfg. Rename resctrl_kcfg to resctrl_kmode, ctrl_mode
    to ctrl, mon_mode to mon, and k_rdtgrp to rdtgrp. Comments describe
    the objects, not a member list. Rewrite changelog.

v5: Replace per-mode registration helpers with a single resctrl_kmode_cfg
    structure. Derive ctrl_en and mon_en from resctrl_arch_alloc_capable()
    and resctrl_arch_mon_capable() during filesystem init. Update code
    comments and changelog.

v4: New patch to initialize supported kernel modes.
    https://lore.kernel.org/lkml/737a4228-52fb-4583-ac64-8efe79c107e6@xxxxxxxxx/
    Changed the kmode_cur to enum resctrl_kernel_mode in resctrl_kmode_cfg.
    Moved the resctrl_kmode_cfg to filesystem code.
---
 fs/resctrl/internal.h | 29 +++++++++++++++++++++++++++++
 fs/resctrl/rdtgroup.c | 25 +++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index e62a277dee85..98f04a2a762b 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -314,6 +314,35 @@ struct mbm_state {
 	u32	prev_bw;
 };
 
+/**
+ * enum kmode_state - Control or monitoring association
+ * @KMODE_INHERIT: Inherit from the user-space task.
+ * @KMODE_ASSIGN: Use the backing group's CLOSID or RMID.
+ */
+enum kmode_state {
+	KMODE_INHERIT,
+	KMODE_ASSIGN
+};
+
+/**
+ * struct resctrl_kmode_cfg - Kernel mode configuration
+ * @kmode_sup:	Bitmap of supported kernel modes.
+ * @kmode_cur:	Currently selected kernel mode.
+ * @ctrl:	Control association for %RESCTRL_GLOBAL_ENABLE_PER_CPU.
+ *		Kept while %RESCTRL_INHERIT_USER is selected.
+ * @mon:	Monitoring association for %RESCTRL_GLOBAL_ENABLE_PER_CPU.
+ *		Kept while %RESCTRL_INHERIT_USER is selected.
+ * @rdtgrp:	Resource group backing %RESCTRL_GLOBAL_ENABLE_PER_CPU.
+ *		%NULL while that mode is not selected.
+ */
+struct resctrl_kmode_cfg {
+	DECLARE_BITMAP(kmode_sup, RESCTRL_NUM_KERNEL_MODES);
+	enum resctrl_kernel_mode	kmode_cur;
+	enum kmode_state		ctrl;
+	enum kmode_state		mon;
+	struct rdtgroup			*rdtgrp;
+};
+
 extern struct mutex rdtgroup_mutex;
 
 static inline const char *rdt_kn_name(const struct kernfs_node *kn)
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 68be9b903ac6..7c39792be1fa 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -76,6 +76,9 @@ static void rdtgroup_destroy_root(void);
 
 struct dentry *debugfs_resctrl;
 
+/* Kernel mode for this system. */
+static struct resctrl_kmode_cfg resctrl_kmode;
+
 /*
  * Memory bandwidth monitoring event to use for the default CTRL_MON group
  * and each new CTRL_MON group created by the user.  Only relevant when
@@ -2297,6 +2300,26 @@ static void io_alloc_init(void)
 	}
 }
 
+/*
+ * Set RESCTRL_INHERIT_USER as the default when the platform supports
+ * allocation or monitoring. Otherwise leave kernel mode unsupported.
+ */
+static void resctrl_kmode_init(void)
+{
+	if (!resctrl_arch_alloc_capable() && !resctrl_arch_mon_capable())
+		return;
+
+	resctrl_kmode.kmode_cur = RESCTRL_INHERIT_USER;
+	__set_bit(RESCTRL_INHERIT_USER, resctrl_kmode.kmode_sup);
+
+	/*
+	 * Defaults used when RESCTRL_GLOBAL_ENABLE_PER_CPU mode is
+	 * activated without new values.
+	 */
+	resctrl_kmode.ctrl = KMODE_ASSIGN;
+	resctrl_kmode.mon = KMODE_ASSIGN;
+}
+
 void resctrl_file_fflags_init(const char *config, unsigned long fflags)
 {
 	struct rftype *rft;
@@ -4814,6 +4837,8 @@ int resctrl_init(void)
 	if (ret)
 		return ret;
 
+	resctrl_kmode_init();
+
 	ret = sysfs_create_mount_point(fs_kobj, "resctrl");
 	if (ret) {
 		resctrl_l3_mon_resource_exit();
-- 
2.43.0