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Message-ID: <a54bb4c58ee1bf44284af0a9f50ce32dd15383b0.1769029977.git.babu.moger@amd.com>
Date: Wed, 21 Jan 2026 15:12:54 -0600
From: Babu Moger <babu.moger@....com>
To: <corbet@....net>, <tony.luck@...el.com>, <reinette.chatre@...el.com>,
<Dave.Martin@....com>, <james.morse@....com>, <babu.moger@....com>,
<tglx@...nel.org>, <mingo@...hat.com>, <bp@...en8.de>,
<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <peterz@...radead.org>,
<juri.lelli@...hat.com>, <vincent.guittot@...aro.org>,
<dietmar.eggemann@....com>, <rostedt@...dmis.org>, <bsegall@...gle.com>,
<mgorman@...e.de>, <vschneid@...hat.com>, <akpm@...ux-foundation.org>,
<pawan.kumar.gupta@...ux.intel.com>, <pmladek@...e.com>,
<feng.tang@...ux.alibaba.com>, <kees@...nel.org>, <arnd@...db.de>,
<fvdl@...gle.com>, <lirongqing@...du.com>, <bhelgaas@...gle.com>,
<seanjc@...gle.com>, <xin@...or.com>, <manali.shukla@....com>,
<dapeng1.mi@...ux.intel.com>, <chang.seok.bae@...el.com>,
<mario.limonciello@....com>, <naveen@...nel.org>,
<elena.reshetova@...el.com>, <thomas.lendacky@....com>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<kvm@...r.kernel.org>, <peternewman@...gle.com>, <eranian@...gle.com>,
<gautham.shenoy@....com>
Subject: [RFC PATCH 16/19] fs/resctrl: Implement rdtgroup_plza_write() to configure PLZA in a group
Introduce rdtgroup_plza_write() group which enables per group control of
PLZA through the resctrl filesystem and ensure that enabling or disabling
PLZA is propagated consistently across all CPUs belonging to the group.
Enforce the capability checks, exclude default, pseudo-locked and CTRL_MON
groups with sub monitors. Also, ensure that only one group can have PLZA
enabled at a time.
Signed-off-by: Babu Moger <babu.moger@....com>
---
Documentation/filesystems/resctrl.rst | 5 ++
fs/resctrl/rdtgroup.c | 88 ++++++++++++++++++++++++++-
2 files changed, 92 insertions(+), 1 deletion(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 1de55b5cb0e3..8edcc047ffe5 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -626,6 +626,11 @@ When control is enabled all CTRL_MON groups will also contain:
Available only with debug option. The identifier used by hardware
for the control group. On x86 this is the CLOSID.
+"plza":
+ When enabled, CPUs or tasks in the resctrl group follow the group's
+ limits while running at Privilege Level 0 (CPL-0). This can only be
+ enabled for CTRL_MON groups.
+
When monitoring is enabled all MON groups will also contain:
"mon_data":
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index d467b52a0c74..042ae7d63aea 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -896,6 +896,76 @@ static int rdtgroup_plza_show(struct kernfs_open_file *of,
return ret;
}
+static ssize_t rdtgroup_plza_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off)
+{
+ struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
+ struct rdtgroup *rdtgrp, *prgrp;
+ int cpu, ret = 0;
+ bool enable;
+
+ ret = kstrtobool(buf, &enable);
+ if (ret)
+ return ret;
+
+ rdtgrp = rdtgroup_kn_lock_live(of->kn);
+ if (!rdtgrp) {
+ rdtgroup_kn_unlock(of->kn);
+ return -ENOENT;
+ }
+
+ rdt_last_cmd_clear();
+
+ if (!r->plza_capable) {
+ rdt_last_cmd_puts("PLZA is not supported in the system\n");
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ if (rdtgrp == &rdtgroup_default) {
+ rdt_last_cmd_puts("Cannot set PLZA on a default group\n");
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) {
+ rdt_last_cmd_puts("Resource group is pseudo-locked\n");
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ if (!list_empty(&rdtgrp->mon.crdtgrp_list)) {
+ rdt_last_cmd_puts("Cannot change CTRL_MON group with sub monitor groups\n");
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
+ if (prgrp == rdtgrp)
+ continue;
+ if (enable && prgrp->plza) {
+ rdt_last_cmd_puts("PLZA is already configured on another group\n");
+ ret = -EINVAL;
+ goto unlock;
+ }
+ }
+
+ /* Enable or disable PLZA state and update per CPU state if there is a change */
+ if (enable != rdtgrp->plza) {
+ resctrl_arch_plza_setup(r, rdtgrp->closid, rdtgrp->mon.rmid);
+
+ for_each_cpu(cpu, &rdtgrp->cpu_mask)
+ resctrl_arch_set_cpu_plza(cpu, rdtgrp->closid,
+ rdtgrp->mon.rmid, enable);
+ rdtgrp->plza = enable;
+ }
+
+unlock:
+ rdtgroup_kn_unlock(of->kn);
+
+ return ret ?: nbytes;
+}
+
#ifdef CONFIG_PROC_CPU_RESCTRL
/*
* A task can only be part of one resctrl control group and of one monitor
@@ -2171,8 +2241,9 @@ static struct rftype res_common_files[] = {
},
{
.name = "plza",
- .mode = 0444,
+ .mode = 0644,
.kf_ops = &rdtgroup_kf_single_ops,
+ .write = rdtgroup_plza_write,
.seq_show = rdtgroup_plza_show,
},
};
@@ -3126,11 +3197,19 @@ static void free_all_child_rdtgrp(struct rdtgroup *rdtgrp)
static void rmdir_all_sub(void)
{
struct rdtgroup *rdtgrp, *tmp;
+ int cpu;
/* Move all tasks to the default resource group */
rdt_move_group_tasks(NULL, &rdtgroup_default, NULL);
list_for_each_entry_safe(rdtgrp, tmp, &rdt_all_groups, rdtgroup_list) {
+ if (rdtgrp->plza) {
+ for_each_cpu(cpu, &rdtgrp->cpu_mask)
+ resctrl_arch_set_cpu_plza(cpu, rdtgrp->closid,
+ rdtgrp->mon.rmid, false);
+ rdtgrp->plza = 0;
+ }
+
/* Free any child rmids */
free_all_child_rdtgrp(rdtgrp);
@@ -4090,6 +4169,13 @@ static int rdtgroup_rmdir_ctrl(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
u32 closid, rmid;
int cpu;
+ if (rdtgrp->plza) {
+ for_each_cpu(cpu, &rdtgrp->cpu_mask)
+ resctrl_arch_set_cpu_plza(cpu, rdtgrp->closid,
+ rdtgrp->mon.rmid, false);
+ rdtgrp->plza = 0;
+ }
+
/* Give any tasks back to the default group */
rdt_move_group_tasks(rdtgrp, &rdtgroup_default, tmpmask);
--
2.34.1
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