[RFC PATCH 05/10] fs/resctrl: Prepare for range-format pseudo resources

[Jinjie Ruan]

arm_mpam exposes the MPAM priority, capacity and limit controls as
extra resources that reuse the schema machinery but have no resource
of their own: they share the base resource's class, domains and
components, and only the mpam_config field written differs.

Prepare the resctrl core for them:
- Add RDT_RESOURCE_L{2,3}_{MAX,MIN,PRI} and RDT_RESOURCE_MB_{MIN,PRI,
  HDL,OPT} slots after PERF_PKG. The entries are unconditional; an
  architecture only gets dead slots it never initialises.
- Dispatch rdtgroup_init_alloc(), rdtgroup_size_show() and
  rdtgroup_mode_test_exclusive() on schema_fmt instead of the MBA/SMBA
  rids, so every RESCTRL_SCHEMA_RANGE resource takes the percentage path.
- Skip the pseudo rids in fflags_from_resource() and
  rdtgroup_create_info_dir(): they are only reachable through schemata.
- resctrl_get_default_ctrl() returns the defaults for the pseudo rids.

No behaviour change until an architecture populates the slots.

Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
---
 fs/resctrl/rdtgroup.c   | 15 ++++++++++-----
 include/linux/resctrl.h | 33 +++++++++++++++++++++++++++++++--
 2 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 5dcbb0a964e8..bdc568bb13d6 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1491,7 +1491,8 @@ static bool rdtgroup_mode_test_exclusive(struct rdtgroup *rdtgrp)
 
 	list_for_each_entry(s, &resctrl_schema_all, list) {
 		r = s->res;
-		if (r->rid == RDT_RESOURCE_MBA || r->rid == RDT_RESOURCE_SMBA)
+		/* Only the bitmap resources are caches with CBM semantics */
+		if (r->schema_fmt == RESCTRL_SCHEMA_RANGE)
 			continue;
 		has_cache = true;
 		list_for_each_entry_rcu(d, &r->ctrl_domains, hdr.list, lockdep_is_cpus_held()) {
@@ -1696,8 +1697,7 @@ static int rdtgroup_size_show(struct kernfs_open_file *of,
 					ctrl = resctrl_arch_get_config(r, d,
 								       closid,
 								       type);
-				if (r->rid == RDT_RESOURCE_MBA ||
-				    r->rid == RDT_RESOURCE_SMBA)
+				if (r->schema_fmt == RESCTRL_SCHEMA_RANGE)
 					size = ctrl;
 				else
 					size = rdtgroup_cbm_to_size(r, d, ctrl);
@@ -2497,6 +2497,9 @@ static unsigned long fflags_from_resource(struct rdt_resource *r)
 		return RFTYPE_RES_MB;
 	case RDT_RESOURCE_PERF_PKG:
 		return RFTYPE_RES_PERF_PKG;
+	default:
+		/* The pseudo resources have no info directory of their own */
+		break;
 	}
 
 	return WARN_ON_ONCE(1);
@@ -2522,6 +2525,9 @@ static int rdtgroup_create_info_dir(struct kernfs_node *parent_kn)
 	/* loop over enabled controls, these are all alloc_capable */
 	list_for_each_entry(s, &resctrl_schema_all, list) {
 		r = s->res;
+		/* The pseudo resources are only reachable through schemata */
+		if (r->rid >= RDT_RESOURCE_L3_MAX)
+			continue;
 		fflags = fflags_from_resource(r) | RFTYPE_CTRL_INFO;
 		ret = rdtgroup_mkdir_info_resdir(s, s->name, fflags);
 		if (ret)
@@ -3859,8 +3865,7 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
 
 	list_for_each_entry(s, &resctrl_schema_all, list) {
 		r = s->res;
-		if (r->rid == RDT_RESOURCE_MBA ||
-		    r->rid == RDT_RESOURCE_SMBA) {
+		if (r->schema_fmt == RESCTRL_SCHEMA_RANGE) {
 			rdtgroup_init_mba(r, rdtgrp->closid);
 			if (is_mba_sc(r))
 				continue;
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index dd09c2ce9a0f..33af56f953c0 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -54,7 +54,23 @@ enum resctrl_res_level {
 	RDT_RESOURCE_MBA,
 	RDT_RESOURCE_SMBA,
 	RDT_RESOURCE_PERF_PKG,
-	RDT_RESOURCE_LAST = RDT_RESOURCE_PERF_PKG
+	/*
+	 * Pseudo resources re-using the class picked for the resource above
+	 * to expose the MPAM priority/capacity/limit controls. They have no
+	 * class of their own, share the base resource's domains, and never
+	 * appear in info/.
+	 */
+	RDT_RESOURCE_L3_MAX,
+	RDT_RESOURCE_L2_MAX,
+	RDT_RESOURCE_L3_MIN,
+	RDT_RESOURCE_L2_MIN,
+	RDT_RESOURCE_MB_MIN,
+	RDT_RESOURCE_L3_PRI,
+	RDT_RESOURCE_L2_PRI,
+	RDT_RESOURCE_MB_PRI,
+	RDT_RESOURCE_MB_HDL,
+	RDT_RESOURCE_MB_OPT,
+	RDT_RESOURCE_LAST = RDT_RESOURCE_MB_OPT
 };
 
 #define RDT_NUM_RESOURCES (RDT_RESOURCE_LAST + 1)
@@ -408,7 +424,20 @@ static inline u32 resctrl_get_default_ctrl(struct rdt_resource *r)
 	case RESCTRL_SCHEMA_BITMAP:
 		return BIT_MASK(r->cache.cbm_len) - 1;
 	case RESCTRL_SCHEMA_RANGE:
-		return r->membw.max_bw;
+		switch (r->rid) {
+		case RDT_RESOURCE_L3_MIN:
+		case RDT_RESOURCE_L2_MIN:
+		case RDT_RESOURCE_MB_MIN:
+		case RDT_RESOURCE_L3_PRI:
+		case RDT_RESOURCE_L2_PRI:
+			return 0;
+		case RDT_RESOURCE_MB_PRI:
+			return 3;
+		case RDT_RESOURCE_MB_HDL:
+			return 1;
+		default:
+			return r->membw.max_bw;
+		}
 	}
 
 	return WARN_ON_ONCE(1);
-- 
2.34.1