[PATCH 05/23] resctrl: Add nested resource_schemata support for emulated controls
Fenghua Yu
fenghuay at nvidia.com
Thu Jul 16 14:02:55 PDT 2026
Some architectures expose an alternate, hardware-native control that
emulates a legacy control (for example a node-scoped bandwidth control
emulating the L3-shaped MB control). Represent this relationship with a
new resctrl_ctrl::emulated_by pointer stored on the emulated (default)
control, pointing at the control that emulates it, and add a
RESCTRL_CTRL_NAME_NODE control name for the node-scoped variant.
Build the resource_schemata tree accordingly: create the default control
directory first, then nest each emulating control beneath the default
control it emulates, while non-emulated controls remain directly under
resource_schemata. Creating the default directory up front makes the
layout independent of the order controls appear in the list.
Architecture backends set emulated_by during control init; until then the
nesting branch is never taken and all controls remain directly under
resource_schemata.
Factor the per-control directory creation into
resctrl_ctrl_create_subdir() and fix its error and ownership handling so
the newly created directory (not its parent) is validated and gets its
uid/gid applied.
Signed-off-by: Fenghua Yu <fenghuay at nvidia.com>
---
arch/x86/kernel/cpu/resctrl/core.c | 2 +
fs/resctrl/ctrlmondata.c | 1 +
fs/resctrl/rdtgroup.c | 67 ++++++++++++++++++++++++------
include/linux/resctrl.h | 7 +++-
4 files changed, 63 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 07c6ebb7fc43..5575a16caeab 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -214,6 +214,8 @@ static __init bool __temporary_multiple_mba_intel_controls(struct rdt_resource *
case RESCTRL_CTRL_NAME_MAX:
hw_ctrl->msr_update = update_temporary_max;
break;
+ default:
+ break;
}
return true;
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index d95ab8ad36e2..1f832a838115 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -304,6 +304,7 @@ static const char * const resctrl_ctrl_name[] = {
[RESCTRL_CTRL_NAME_DEF] = "",
[RESCTRL_CTRL_NAME_MIN] = "MIN",
[RESCTRL_CTRL_NAME_MAX] = "MAX",
+ [RESCTRL_CTRL_NAME_NODE] = "NODE",
};
const char *resctrl_ctrl_name_str(enum resctrl_ctrl_name name)
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index a3aad9b1ff6e..3bec23728847 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -2781,6 +2781,26 @@ static int resctrl_ctrl_add_files(struct kernfs_node *kn)
return ret;
}
+static int resctrl_ctrl_create_subdir(struct kernfs_node *kn_dir,
+ struct rdt_resource_final *f,
+ struct resctrl_ctrl *ctrl, struct kernfs_node **kn_ctrl)
+{
+ char ctrl_full_name[20];
+ int ret;
+
+ ret = snprintf(ctrl_full_name, sizeof(ctrl_full_name), "%s%s%s",
+ f->name, resctrl_ctrl_is_default(ctrl) ? "" : "_",
+ resctrl_ctrl_is_default(ctrl) ? "" : resctrl_ctrl_name_str(ctrl->name));
+ if (ret >= sizeof(ctrl_full_name))
+ return -ENOSPC;
+
+ *kn_ctrl = kernfs_create_dir(kn_dir, ctrl_full_name, kn_dir->mode, ctrl);
+ if (IS_ERR(*kn_ctrl))
+ return PTR_ERR(*kn_ctrl);
+
+ return rdtgroup_kn_set_ugid(*kn_ctrl);
+}
+
/*
* No need to cleanup on exit - caller calls the recursive kernfs_remove()
* on failure.
@@ -2788,10 +2808,9 @@ static int resctrl_ctrl_add_files(struct kernfs_node *kn)
static int resctrl_mkdir_schemata_dir(struct kernfs_node *kn,
struct rdt_resource_final *f)
{
- struct kernfs_node *kn_subdir, *kn_ctrl;
+ struct kernfs_node *kn_subdir, *kn_ctrl, *kn_ctrl_def = NULL;
+ struct resctrl_ctrl *ctrl, *ctrl_def = NULL;
struct rdt_resource *r = f->res;
- struct resctrl_ctrl *ctrl;
- char ctrl_full_name[20];
int ret;
kn_subdir = kernfs_create_dir(kn, "resource_schemata", kn->mode, f);
@@ -2808,19 +2827,41 @@ static int resctrl_mkdir_schemata_dir(struct kernfs_node *kn,
return ret;
}
+ /*
+ * Create the default control sub-dir first. Emulated controls are
+ * nested underneath it and may be iterated before it, so it has to
+ * exist before the rest of the controls are created.
+ */
for_each_resource_ctrl(ctrl, f->res) {
- ret = snprintf(ctrl_full_name, sizeof(ctrl_full_name), "%s%s%s",
- f->name, resctrl_ctrl_is_default(ctrl) ? "" : "_",
- resctrl_ctrl_is_default(ctrl) ? "" : resctrl_ctrl_name_str(ctrl->name));
- if (ret >= sizeof(ctrl_full_name))
- return -ENOSPC;
+ if (ctrl->name != RESCTRL_CTRL_NAME_DEF)
+ continue;
- kn_ctrl = kernfs_create_dir(kn_subdir, ctrl_full_name, kn_subdir->mode,
- ctrl);
- if (IS_ERR(kn_ctrl))
- return PTR_ERR(kn_ctrl);
+ ret = resctrl_ctrl_create_subdir(kn_subdir, f, ctrl, &kn_ctrl_def);
+ if (ret)
+ return ret;
+ ret = resctrl_add_ctrl_files(kn_ctrl_def, ctrl);
+ if (ret)
+ return ret;
+ ctrl_def = ctrl;
+ break;
+ }
- ret = rdtgroup_kn_set_ugid(kn_ctrl);
+ for_each_resource_ctrl(ctrl, f->res) {
+ if (ctrl->name == RESCTRL_CTRL_NAME_DEF)
+ continue;
+
+ /*
+ * In legacy mode the emulating control is nested under the
+ * default control it emulates (the default control's
+ * emulated_by points at it). In native mode there is no
+ * emulation, so every control sits directly under
+ * resource_schemata.
+ */
+ if (r->mode == RESCTRL_CTRL_LEGACY &&
+ ctrl_def && ctrl_def->emulated_by == ctrl)
+ ret = resctrl_ctrl_create_subdir(kn_ctrl_def, f, ctrl, &kn_ctrl);
+ else
+ ret = resctrl_ctrl_create_subdir(kn_subdir, f, ctrl, &kn_ctrl);
if (ret)
return ret;
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 5d8ea12ae16b..06482e766087 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -362,12 +362,14 @@ struct resctrl_mon {
* has the same name as the resource.
* @RESCTRL_CTRL_NAME_MIN: "MIN"
* @RESCTRL_CTRL_NAME_MAX: "MAX"
+ * @RESCTRL_CTRL_NAME_NODE: "NODE"
*/
enum resctrl_ctrl_name {
RESCTRL_CTRL_NAME_DEF,
RESCTRL_CTRL_NAME_MIN,
RESCTRL_CTRL_NAME_MAX,
- RESCTRL_CTRL_NAME_LAST = RESCTRL_CTRL_NAME_MAX
+ RESCTRL_CTRL_NAME_NODE,
+ RESCTRL_CTRL_NAME_LAST = RESCTRL_CTRL_NAME_NODE
};
/**
@@ -383,6 +385,8 @@ enum resctrl_ctrl_name {
* Specifically, "rdt_resource_final::name"_"resctrl_ctrl::name".
* For example, with resource name "MB" and control name "MAX" the
* schema entry will be "MB_MAX".
+ * @emulated_by: For an emulated control, points at the control that emulates
+ * it; NULL if this control is not emulated.
* @cache: Cache allocation control properties.
* @membw: Bandwidth control properties.
*/
@@ -392,6 +396,7 @@ struct resctrl_ctrl {
struct list_head domains;
enum resctrl_ctrl_type type;
enum resctrl_ctrl_name name;
+ struct resctrl_ctrl *emulated_by;
union {
struct resctrl_cache cache;
struct resctrl_membw membw;
--
2.43.0
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