Merge tag 'x86_cache_for_v6.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 resource control updates from Borislav Petkov:
 "Carve out the resctrl filesystem-related code into fs/resctrl/ so that
  multiple architectures can share the fs API for manipulating their
  respective hw resource control implementation.

  This is the second step in the work towards sharing the resctrl
  filesystem interface, the next one being plugging ARM's MPAM into the
  aforementioned fs API"

* tag 'x86_cache_for_v6.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
  MAINTAINERS: Add reviewers for fs/resctrl
  x86,fs/resctrl: Move the resctrl filesystem code to live in /fs/resctrl
  x86/resctrl: Always initialise rid field in rdt_resources_all[]
  x86/resctrl: Relax some asm #includes
  x86/resctrl: Prefer alloc(sizeof(*foo)) idiom in rdt_init_fs_context()
  x86/resctrl: Squelch whitespace anomalies in resctrl core code
  x86/resctrl: Move pseudo lock prototypes to include/linux/resctrl.h
  x86/resctrl: Fix types in resctrl_arch_mon_ctx_{alloc,free}() stubs
  x86/resctrl: Move enum resctrl_event_id to resctrl.h
  x86/resctrl: Move the filesystem bits to headers visible to fs/resctrl
  fs/resctrl: Add boiler plate for external resctrl code
  x86/resctrl: Add 'resctrl' to the title of the resctrl documentation
  x86/resctrl: Split trace.h
  x86/resctrl: Expand the width of domid by replacing mon_data_bits
  x86/resctrl: Add end-marker to the resctrl_event_id enum
  x86/resctrl: Move is_mba_sc() out of core.c
  x86/resctrl: Drop __init/__exit on assorted symbols
  x86/resctrl: Resctrl_exit() teardown resctrl but leave the mount point
  x86/resctrl: Check all domains are offline in resctrl_exit()
  x86/resctrl: Rename resctrl_sched_in() to begin with "resctrl_arch_"
  ...

1 files changed, 661 insertions, 0 deletions

diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
new file mode 100644
index 0000000000000..6ed2dfd4dbbd9
--- /dev/null
+++ b/fs/resctrl/ctrlmondata.c
@@ -0,0 +1,661 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Resource Director Technology(RDT)
+ * - Cache Allocation code.
+ *
+ * Copyright (C) 2016 Intel Corporation
+ *
+ * Authors:
+ *    Fenghua Yu <fenghua.yu@intel.com>
+ *    Tony Luck <tony.luck@intel.com>
+ *
+ * More information about RDT be found in the Intel (R) x86 Architecture
+ * Software Developer Manual June 2016, volume 3, section 17.17.
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/cpu.h>
+#include <linux/kernfs.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/tick.h>
+
+#include "internal.h"
+
+struct rdt_parse_data {
+	struct rdtgroup		*rdtgrp;
+	char			*buf;
+};
+
+typedef int (ctrlval_parser_t)(struct rdt_parse_data *data,
+			       struct resctrl_schema *s,
+			       struct rdt_ctrl_domain *d);
+
+/*
+ * Check whether MBA bandwidth percentage value is correct. The value is
+ * checked against the minimum and max bandwidth values specified by the
+ * hardware. The allocated bandwidth percentage is rounded to the next
+ * control step available on the hardware.
+ */
+static bool bw_validate(char *buf, u32 *data, struct rdt_resource *r)
+{
+	int ret;
+	u32 bw;
+
+	/*
+	 * Only linear delay values is supported for current Intel SKUs.
+	 */
+	if (!r->membw.delay_linear && r->membw.arch_needs_linear) {
+		rdt_last_cmd_puts("No support for non-linear MB domains\n");
+		return false;
+	}
+
+	ret = kstrtou32(buf, 10, &bw);
+	if (ret) {
+		rdt_last_cmd_printf("Invalid MB value %s\n", buf);
+		return false;
+	}
+
+	/* Nothing else to do if software controller is enabled. */
+	if (is_mba_sc(r)) {
+		*data = bw;
+		return true;
+	}
+
+	if (bw < r->membw.min_bw || bw > r->membw.max_bw) {
+		rdt_last_cmd_printf("MB value %u out of range [%d,%d]\n",
+				    bw, r->membw.min_bw, r->membw.max_bw);
+		return false;
+	}
+
+	*data = roundup(bw, (unsigned long)r->membw.bw_gran);
+	return true;
+}
+
+static int parse_bw(struct rdt_parse_data *data, struct resctrl_schema *s,
+		    struct rdt_ctrl_domain *d)
+{
+	struct resctrl_staged_config *cfg;
+	u32 closid = data->rdtgrp->closid;
+	struct rdt_resource *r = s->res;
+	u32 bw_val;
+
+	cfg = &d->staged_config[s->conf_type];
+	if (cfg->have_new_ctrl) {
+		rdt_last_cmd_printf("Duplicate domain %d\n", d->hdr.id);
+		return -EINVAL;
+	}
+
+	if (!bw_validate(data->buf, &bw_val, r))
+		return -EINVAL;
+
+	if (is_mba_sc(r)) {
+		d->mbps_val[closid] = bw_val;
+		return 0;
+	}
+
+	cfg->new_ctrl = bw_val;
+	cfg->have_new_ctrl = true;
+
+	return 0;
+}
+
+/*
+ * Check whether a cache bit mask is valid.
+ * On Intel CPUs, non-contiguous 1s value support is indicated by CPUID:
+ *   - CPUID.0x10.1:ECX[3]: L3 non-contiguous 1s value supported if 1
+ *   - CPUID.0x10.2:ECX[3]: L2 non-contiguous 1s value supported if 1
+ *
+ * Haswell does not support a non-contiguous 1s value and additionally
+ * requires at least two bits set.
+ * AMD allows non-contiguous bitmasks.
+ */
+static bool cbm_validate(char *buf, u32 *data, struct rdt_resource *r)
+{
+	u32 supported_bits = BIT_MASK(r->cache.cbm_len) - 1;
+	unsigned int cbm_len = r->cache.cbm_len;
+	unsigned long first_bit, zero_bit, val;
+	int ret;
+
+	ret = kstrtoul(buf, 16, &val);
+	if (ret) {
+		rdt_last_cmd_printf("Non-hex character in the mask %s\n", buf);
+		return false;
+	}
+
+	if ((r->cache.min_cbm_bits > 0 && val == 0) || val > supported_bits) {
+		rdt_last_cmd_puts("Mask out of range\n");
+		return false;
+	}
+
+	first_bit = find_first_bit(&val, cbm_len);
+	zero_bit = find_next_zero_bit(&val, cbm_len, first_bit);
+
+	/* Are non-contiguous bitmasks allowed? */
+	if (!r->cache.arch_has_sparse_bitmasks &&
+	    (find_next_bit(&val, cbm_len, zero_bit) < cbm_len)) {
+		rdt_last_cmd_printf("The mask %lx has non-consecutive 1-bits\n", val);
+		return false;
+	}
+
+	if ((zero_bit - first_bit) < r->cache.min_cbm_bits) {
+		rdt_last_cmd_printf("Need at least %d bits in the mask\n",
+				    r->cache.min_cbm_bits);
+		return false;
+	}
+
+	*data = val;
+	return true;
+}
+
+/*
+ * Read one cache bit mask (hex). Check that it is valid for the current
+ * resource type.
+ */
+static int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s,
+		     struct rdt_ctrl_domain *d)
+{
+	struct rdtgroup *rdtgrp = data->rdtgrp;
+	struct resctrl_staged_config *cfg;
+	struct rdt_resource *r = s->res;
+	u32 cbm_val;
+
+	cfg = &d->staged_config[s->conf_type];
+	if (cfg->have_new_ctrl) {
+		rdt_last_cmd_printf("Duplicate domain %d\n", d->hdr.id);
+		return -EINVAL;
+	}
+
+	/*
+	 * Cannot set up more than one pseudo-locked region in a cache
+	 * hierarchy.
+	 */
+	if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP &&
+	    rdtgroup_pseudo_locked_in_hierarchy(d)) {
+		rdt_last_cmd_puts("Pseudo-locked region in hierarchy\n");
+		return -EINVAL;
+	}
+
+	if (!cbm_validate(data->buf, &cbm_val, r))
+		return -EINVAL;
+
+	if ((rdtgrp->mode == RDT_MODE_EXCLUSIVE ||
+	     rdtgrp->mode == RDT_MODE_SHAREABLE) &&
+	    rdtgroup_cbm_overlaps_pseudo_locked(d, cbm_val)) {
+		rdt_last_cmd_puts("CBM overlaps with pseudo-locked region\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * The CBM may not overlap with the CBM of another closid if
+	 * either is exclusive.
+	 */
+	if (rdtgroup_cbm_overlaps(s, d, cbm_val, rdtgrp->closid, true)) {
+		rdt_last_cmd_puts("Overlaps with exclusive group\n");
+		return -EINVAL;
+	}
+
+	if (rdtgroup_cbm_overlaps(s, d, cbm_val, rdtgrp->closid, false)) {
+		if (rdtgrp->mode == RDT_MODE_EXCLUSIVE ||
+		    rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
+			rdt_last_cmd_puts("Overlaps with other group\n");
+			return -EINVAL;
+		}
+	}
+
+	cfg->new_ctrl = cbm_val;
+	cfg->have_new_ctrl = true;
+
+	return 0;
+}
+
+/*
+ * For each domain in this resource we expect to find a series of:
+ *	id=mask
+ * separated by ";". The "id" is in decimal, and must match one of
+ * the "id"s for this resource.
+ */
+static int parse_line(char *line, struct resctrl_schema *s,
+		      struct rdtgroup *rdtgrp)
+{
+	enum resctrl_conf_type t = s->conf_type;
+	ctrlval_parser_t *parse_ctrlval = NULL;
+	struct resctrl_staged_config *cfg;
+	struct rdt_resource *r = s->res;
+	struct rdt_parse_data data;
+	struct rdt_ctrl_domain *d;
+	char *dom = NULL, *id;
+	unsigned long dom_id;
+
+	/* Walking r->domains, ensure it can't race with cpuhp */
+	lockdep_assert_cpus_held();
+
+	switch (r->schema_fmt) {
+	case RESCTRL_SCHEMA_BITMAP:
+		parse_ctrlval = &parse_cbm;
+		break;
+	case RESCTRL_SCHEMA_RANGE:
+		parse_ctrlval = &parse_bw;
+		break;
+	}
+
+	if (WARN_ON_ONCE(!parse_ctrlval))
+		return -EINVAL;
+
+	if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP &&
+	    (r->rid == RDT_RESOURCE_MBA || r->rid == RDT_RESOURCE_SMBA)) {
+		rdt_last_cmd_puts("Cannot pseudo-lock MBA resource\n");
+		return -EINVAL;
+	}
+
+next:
+	if (!line || line[0] == '\0')
+		return 0;
+	dom = strsep(&line, ";");
+	id = strsep(&dom, "=");
+	if (!dom || kstrtoul(id, 10, &dom_id)) {
+		rdt_last_cmd_puts("Missing '=' or non-numeric domain\n");
+		return -EINVAL;
+	}
+	dom = strim(dom);
+	list_for_each_entry(d, &r->ctrl_domains, hdr.list) {
+		if (d->hdr.id == dom_id) {
+			data.buf = dom;
+			data.rdtgrp = rdtgrp;
+			if (parse_ctrlval(&data, s, d))
+				return -EINVAL;
+			if (rdtgrp->mode ==  RDT_MODE_PSEUDO_LOCKSETUP) {
+				cfg = &d->staged_config[t];
+				/*
+				 * In pseudo-locking setup mode and just
+				 * parsed a valid CBM that should be
+				 * pseudo-locked. Only one locked region per
+				 * resource group and domain so just do
+				 * the required initialization for single
+				 * region and return.
+				 */
+				rdtgrp->plr->s = s;
+				rdtgrp->plr->d = d;
+				rdtgrp->plr->cbm = cfg->new_ctrl;
+				d->plr = rdtgrp->plr;
+				return 0;
+			}
+			goto next;
+		}
+	}
+	return -EINVAL;
+}
+
+static int rdtgroup_parse_resource(char *resname, char *tok,
+				   struct rdtgroup *rdtgrp)
+{
+	struct resctrl_schema *s;
+
+	list_for_each_entry(s, &resctrl_schema_all, list) {
+		if (!strcmp(resname, s->name) && rdtgrp->closid < s->num_closid)
+			return parse_line(tok, s, rdtgrp);
+	}
+	rdt_last_cmd_printf("Unknown or unsupported resource name '%s'\n", resname);
+	return -EINVAL;
+}
+
+ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
+				char *buf, size_t nbytes, loff_t off)
+{
+	struct resctrl_schema *s;
+	struct rdtgroup *rdtgrp;
+	struct rdt_resource *r;
+	char *tok, *resname;
+	int ret = 0;
+
+	/* Valid input requires a trailing newline */
+	if (nbytes == 0 || buf[nbytes - 1] != '\n')
+		return -EINVAL;
+	buf[nbytes - 1] = '\0';
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (!rdtgrp) {
+		rdtgroup_kn_unlock(of->kn);
+		return -ENOENT;
+	}
+	rdt_last_cmd_clear();
+
+	/*
+	 * No changes to pseudo-locked region allowed. It has to be removed
+	 * and re-created instead.
+	 */
+	if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) {
+		ret = -EINVAL;
+		rdt_last_cmd_puts("Resource group is pseudo-locked\n");
+		goto out;
+	}
+
+	rdt_staged_configs_clear();
+
+	while ((tok = strsep(&buf, "\n")) != NULL) {
+		resname = strim(strsep(&tok, ":"));
+		if (!tok) {
+			rdt_last_cmd_puts("Missing ':'\n");
+			ret = -EINVAL;
+			goto out;
+		}
+		if (tok[0] == '\0') {
+			rdt_last_cmd_printf("Missing '%s' value\n", resname);
+			ret = -EINVAL;
+			goto out;
+		}
+		ret = rdtgroup_parse_resource(resname, tok, rdtgrp);
+		if (ret)
+			goto out;
+	}
+
+	list_for_each_entry(s, &resctrl_schema_all, list) {
+		r = s->res;
+
+		/*
+		 * Writes to mba_sc resources update the software controller,
+		 * not the control MSR.
+		 */
+		if (is_mba_sc(r))
+			continue;
+
+		ret = resctrl_arch_update_domains(r, rdtgrp->closid);
+		if (ret)
+			goto out;
+	}
+
+	if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
+		/*
+		 * If pseudo-locking fails we keep the resource group in
+		 * mode RDT_MODE_PSEUDO_LOCKSETUP with its class of service
+		 * active and updated for just the domain the pseudo-locked
+		 * region was requested for.
+		 */
+		ret = rdtgroup_pseudo_lock_create(rdtgrp);
+	}
+
+out:
+	rdt_staged_configs_clear();
+	rdtgroup_kn_unlock(of->kn);
+	return ret ?: nbytes;
+}
+
+static void show_doms(struct seq_file *s, struct resctrl_schema *schema, int closid)
+{
+	struct rdt_resource *r = schema->res;
+	struct rdt_ctrl_domain *dom;
+	bool sep = false;
+	u32 ctrl_val;
+
+	/* Walking r->domains, ensure it can't race with cpuhp */
+	lockdep_assert_cpus_held();
+
+	seq_printf(s, "%*s:", max_name_width, schema->name);
+	list_for_each_entry(dom, &r->ctrl_domains, hdr.list) {
+		if (sep)
+			seq_puts(s, ";");
+
+		if (is_mba_sc(r))
+			ctrl_val = dom->mbps_val[closid];
+		else
+			ctrl_val = resctrl_arch_get_config(r, dom, closid,
+							   schema->conf_type);
+
+		seq_printf(s, schema->fmt_str, dom->hdr.id, ctrl_val);
+		sep = true;
+	}
+	seq_puts(s, "\n");
+}
+
+int rdtgroup_schemata_show(struct kernfs_open_file *of,
+			   struct seq_file *s, void *v)
+{
+	struct resctrl_schema *schema;
+	struct rdtgroup *rdtgrp;
+	int ret = 0;
+	u32 closid;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (rdtgrp) {
+		if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
+			list_for_each_entry(schema, &resctrl_schema_all, list) {
+				seq_printf(s, "%s:uninitialized\n", schema->name);
+			}
+		} else if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED) {
+			if (!rdtgrp->plr->d) {
+				rdt_last_cmd_clear();
+				rdt_last_cmd_puts("Cache domain offline\n");
+				ret = -ENODEV;
+			} else {
+				seq_printf(s, "%s:%d=%x\n",
+					   rdtgrp->plr->s->res->name,
+					   rdtgrp->plr->d->hdr.id,
+					   rdtgrp->plr->cbm);
+			}
+		} else {
+			closid = rdtgrp->closid;
+			list_for_each_entry(schema, &resctrl_schema_all, list) {
+				if (closid < schema->num_closid)
+					show_doms(s, schema, closid);
+			}
+		}
+	} else {
+		ret = -ENOENT;
+	}
+	rdtgroup_kn_unlock(of->kn);
+	return ret;
+}
+
+static int smp_mon_event_count(void *arg)
+{
+	mon_event_count(arg);
+
+	return 0;
+}
+
+ssize_t rdtgroup_mba_mbps_event_write(struct kernfs_open_file *of,
+				      char *buf, size_t nbytes, loff_t off)
+{
+	struct rdtgroup *rdtgrp;
+	int ret = 0;
+
+	/* Valid input requires a trailing newline */
+	if (nbytes == 0 || buf[nbytes - 1] != '\n')
+		return -EINVAL;
+	buf[nbytes - 1] = '\0';
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (!rdtgrp) {
+		rdtgroup_kn_unlock(of->kn);
+		return -ENOENT;
+	}
+	rdt_last_cmd_clear();
+
+	if (!strcmp(buf, "mbm_local_bytes")) {
+		if (resctrl_arch_is_mbm_local_enabled())
+			rdtgrp->mba_mbps_event = QOS_L3_MBM_LOCAL_EVENT_ID;
+		else
+			ret = -EINVAL;
+	} else if (!strcmp(buf, "mbm_total_bytes")) {
+		if (resctrl_arch_is_mbm_total_enabled())
+			rdtgrp->mba_mbps_event = QOS_L3_MBM_TOTAL_EVENT_ID;
+		else
+			ret = -EINVAL;
+	} else {
+		ret = -EINVAL;
+	}
+
+	if (ret)
+		rdt_last_cmd_printf("Unsupported event id '%s'\n", buf);
+
+	rdtgroup_kn_unlock(of->kn);
+
+	return ret ?: nbytes;
+}
+
+int rdtgroup_mba_mbps_event_show(struct kernfs_open_file *of,
+				 struct seq_file *s, void *v)
+{
+	struct rdtgroup *rdtgrp;
+	int ret = 0;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+
+	if (rdtgrp) {
+		switch (rdtgrp->mba_mbps_event) {
+		case QOS_L3_MBM_LOCAL_EVENT_ID:
+			seq_puts(s, "mbm_local_bytes\n");
+			break;
+		case QOS_L3_MBM_TOTAL_EVENT_ID:
+			seq_puts(s, "mbm_total_bytes\n");
+			break;
+		default:
+			pr_warn_once("Bad event %d\n", rdtgrp->mba_mbps_event);
+			ret = -EINVAL;
+			break;
+		}
+	} else {
+		ret = -ENOENT;
+	}
+
+	rdtgroup_kn_unlock(of->kn);
+
+	return ret;
+}
+
+struct rdt_domain_hdr *resctrl_find_domain(struct list_head *h, int id,
+					   struct list_head **pos)
+{
+	struct rdt_domain_hdr *d;
+	struct list_head *l;
+
+	list_for_each(l, h) {
+		d = list_entry(l, struct rdt_domain_hdr, list);
+		/* When id is found, return its domain. */
+		if (id == d->id)
+			return d;
+		/* Stop searching when finding id's position in sorted list. */
+		if (id < d->id)
+			break;
+	}
+
+	if (pos)
+		*pos = l;
+
+	return NULL;
+}
+
+void mon_event_read(struct rmid_read *rr, struct rdt_resource *r,
+		    struct rdt_mon_domain *d, struct rdtgroup *rdtgrp,
+		    cpumask_t *cpumask, int evtid, int first)
+{
+	int cpu;
+
+	/* When picking a CPU from cpu_mask, ensure it can't race with cpuhp */
+	lockdep_assert_cpus_held();
+
+	/*
+	 * Setup the parameters to pass to mon_event_count() to read the data.
+	 */
+	rr->rgrp = rdtgrp;
+	rr->evtid = evtid;
+	rr->r = r;
+	rr->d = d;
+	rr->first = first;
+	rr->arch_mon_ctx = resctrl_arch_mon_ctx_alloc(r, evtid);
+	if (IS_ERR(rr->arch_mon_ctx)) {
+		rr->err = -EINVAL;
+		return;
+	}
+
+	cpu = cpumask_any_housekeeping(cpumask, RESCTRL_PICK_ANY_CPU);
+
+	/*
+	 * cpumask_any_housekeeping() prefers housekeeping CPUs, but
+	 * are all the CPUs nohz_full? If yes, pick a CPU to IPI.
+	 * MPAM's resctrl_arch_rmid_read() is unable to read the
+	 * counters on some platforms if its called in IRQ context.
+	 */
+	if (tick_nohz_full_cpu(cpu))
+		smp_call_function_any(cpumask, mon_event_count, rr, 1);
+	else
+		smp_call_on_cpu(cpu, smp_mon_event_count, rr, false);
+
+	resctrl_arch_mon_ctx_free(r, evtid, rr->arch_mon_ctx);
+}
+
+int rdtgroup_mondata_show(struct seq_file *m, void *arg)
+{
+	struct kernfs_open_file *of = m->private;
+	enum resctrl_res_level resid;
+	enum resctrl_event_id evtid;
+	struct rdt_domain_hdr *hdr;
+	struct rmid_read rr = {0};
+	struct rdt_mon_domain *d;
+	struct rdtgroup *rdtgrp;
+	struct rdt_resource *r;
+	struct mon_data *md;
+	int domid, ret = 0;
+
+	rdtgrp = rdtgroup_kn_lock_live(of->kn);
+	if (!rdtgrp) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	md = of->kn->priv;
+	if (WARN_ON_ONCE(!md)) {
+		ret = -EIO;
+		goto out;
+	}
+
+	resid = md->rid;
+	domid = md->domid;
+	evtid = md->evtid;
+	r = resctrl_arch_get_resource(resid);
+
+	if (md->sum) {
+		/*
+		 * This file requires summing across all domains that share
+		 * the L3 cache id that was provided in the "domid" field of the
+		 * struct mon_data. Search all domains in the resource for
+		 * one that matches this cache id.
+		 */
+		list_for_each_entry(d, &r->mon_domains, hdr.list) {
+			if (d->ci->id == domid) {
+				rr.ci = d->ci;
+				mon_event_read(&rr, r, NULL, rdtgrp,
+					       &d->ci->shared_cpu_map, evtid, false);
+				goto checkresult;
+			}
+		}
+		ret = -ENOENT;
+		goto out;
+	} else {
+		/*
+		 * This file provides data from a single domain. Search
+		 * the resource to find the domain with "domid".
+		 */
+		hdr = resctrl_find_domain(&r->mon_domains, domid, NULL);
+		if (!hdr || WARN_ON_ONCE(hdr->type != RESCTRL_MON_DOMAIN)) {
+			ret = -ENOENT;
+			goto out;
+		}
+		d = container_of(hdr, struct rdt_mon_domain, hdr);
+		mon_event_read(&rr, r, d, rdtgrp, &d->hdr.cpu_mask, evtid, false);
+	}
+
+checkresult:
+
+	if (rr.err == -EIO)
+		seq_puts(m, "Error\n");
+	else if (rr.err == -EINVAL)
+		seq_puts(m, "Unavailable\n");
+	else
+		seq_printf(m, "%llu\n", rr.val);
+
+out:
+	rdtgroup_kn_unlock(of->kn);
+	return ret;
+}