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Message-ID: <3a6d3d9dace1a2dec3418eb00150418e9ef7ac98.1761090860.git.babu.moger@amd.com>
Date: Tue, 21 Oct 2025 18:54:52 -0500
From: Babu Moger <babu.moger@....com>
To: <tony.luck@...el.com>, <reinette.chatre@...el.com>, <tglx@...utronix.de>,
<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <corbet@....net>, <Dave.Martin@....com>, <james.morse@....com>,
<babu.moger@....com>, <x86@...nel.org>, <hpa@...or.com>,
<akpm@...ux-foundation.org>, <paulmck@...nel.org>, <rdunlap@...radead.org>,
<pmladek@...e.com>, <kees@...nel.org>, <arnd@...db.de>, <fvdl@...gle.com>,
<seanjc@...gle.com>, <pawan.kumar.gupta@...ux.intel.com>, <xin@...or.com>,
<thomas.lendacky@....com>, <sohil.mehta@...el.com>, <jarkko@...nel.org>,
<chang.seok.bae@...el.com>, <ebiggers@...gle.com>,
<elena.reshetova@...el.com>, <ak@...ux.intel.com>,
<mario.limonciello@....com>, <perry.yuan@....com>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<peternewman@...gle.com>
Subject: [PATCH v10 09/10] fs/resctrl: Introduce interface to modify io_alloc capacity bitmasks
The io_alloc feature in resctrl enables system software to configure the
portion of the cache allocated for I/O traffic. When supported, the
io_alloc_cbm file in resctrl provides access to capacity bitmasks (CBMs)
allocated for I/O devices.
Enable users to modify io_alloc CBMs by writing to the io_alloc_cbm resctrl
file when the io_alloc feature is enabled.
Mirror the CBMs between CDP_CODE and CDP_DATA when CDP is enabled to present
consistent I/O allocation information to user space.
Signed-off-by: Babu Moger <babu.moger@....com>
---
v10: Updated the changelog.
Updated the return code to EINVAL when feature is not enabled.
Minor code comment update.
v9: Rewrote the changelog.
Removed duplicated rdt_last_cmd_clear().
Corrected rdt_staged_configs_clear() placement.
Added one more example to update the schemata with multiple domains.
Copied staged_config from peer when CDP is enabled.
v8: Updated changelog.
Moved resctrl_io_alloc_parse_line() and resctrl_io_alloc_cbm_write() to
fs/resctrl/ctrlmondata.c.
Added resctrl_arch_get_cdp_enabled() check inside resctrl_io_alloc_parse_line().
Made parse_cbm() static again as everything moved to ctrlmondata.c.
v7: Updated changelog.
Updated CBMs for both CDP_DATA and CDP_CODE when CDP is enabled.
v6: Updated the user doc restctr.doc for minor texts.
Changed the subject to fs/resctrl.
v5: Changes due to FS/ARCH code restructure. The files monitor.c/rdtgroup.c
have been split between FS and ARCH directories.
Changed the code to access the CBMs via either L3CODE or L3DATA resources.
v4: Removed resctrl_io_alloc_parse_cbm and called parse_cbm() directly.
v3: Minor changes due to changes in resctrl_arch_get_io_alloc_enabled()
and resctrl_io_alloc_closid_get().
Taken care of handling the CBM update when CDP is enabled.
Updated the commit log to make it generic.
v2: Added more generic text in documentation.
---
Documentation/filesystems/resctrl.rst | 12 ++++
fs/resctrl/ctrlmondata.c | 93 +++++++++++++++++++++++++++
fs/resctrl/internal.h | 3 +
fs/resctrl/rdtgroup.c | 3 +-
4 files changed, 110 insertions(+), 1 deletion(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 1826120ab5d5..dab4b430d3a3 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -189,6 +189,18 @@ related to allocation:
# cat /sys/fs/resctrl/info/L3/io_alloc_cbm
0=ffff;1=ffff
+ CBMs can be configured by writing to the interface.
+
+ Example::
+
+ # echo 1=ff > /sys/fs/resctrl/info/L3/io_alloc_cbm
+ # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
+ 0=ffff;1=00ff
+
+ # echo "0=ff;1=f" > /sys/fs/resctrl/info/L3/io_alloc_cbm
+ # cat /sys/fs/resctrl/info/L3/io_alloc_cbm
+ 0=00ff;1=000f
+
When CDP is enabled "io_alloc_cbm" associated with the CDP_DATA and CDP_CODE
resources may reflect the same values. For example, values read from and
written to /sys/fs/resctrl/info/L3DATA/io_alloc_cbm may be reflected by
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index 813e298c48d8..a15479dd74a9 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -860,3 +860,96 @@ int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, struct seq_file *seq,
cpus_read_unlock();
return ret;
}
+
+static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
+ struct resctrl_schema *s, u32 closid)
+{
+ enum resctrl_conf_type peer_type;
+ struct rdt_parse_data data;
+ struct rdt_ctrl_domain *d;
+ char *dom = NULL, *id;
+ unsigned long dom_id;
+
+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.mode = RDT_MODE_SHAREABLE;
+ data.closid = closid;
+ if (parse_cbm(&data, s, d))
+ return -EINVAL;
+ /*
+ * Keep io_alloc CLOSID's CBM of CDP_CODE and CDP_DATA
+ * in sync.
+ */
+ if (resctrl_arch_get_cdp_enabled(r->rid)) {
+ peer_type = resctrl_peer_type(s->conf_type);
+ memcpy(&d->staged_config[peer_type],
+ &d->staged_config[s->conf_type],
+ sizeof(d->staged_config[0]));
+ }
+ goto next;
+ }
+ }
+
+ return -EINVAL;
+}
+
+ssize_t resctrl_io_alloc_cbm_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off)
+{
+ struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
+ struct rdt_resource *r = s->res;
+ u32 io_alloc_closid;
+ int ret = 0;
+
+ /* Valid input requires a trailing newline */
+ if (nbytes == 0 || buf[nbytes - 1] != '\n')
+ return -EINVAL;
+
+ buf[nbytes - 1] = '\0';
+
+ cpus_read_lock();
+ mutex_lock(&rdtgroup_mutex);
+ rdt_last_cmd_clear();
+
+ if (!r->cache.io_alloc_capable) {
+ rdt_last_cmd_printf("io_alloc is not supported on %s\n", s->name);
+ ret = -ENODEV;
+ goto out_unlock;
+ }
+
+ if (!resctrl_arch_get_io_alloc_enabled(r)) {
+ rdt_last_cmd_printf("io_alloc is not enabled on %s\n", s->name);
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ io_alloc_closid = resctrl_io_alloc_closid(r);
+
+ rdt_staged_configs_clear();
+ ret = resctrl_io_alloc_parse_line(buf, r, s, io_alloc_closid);
+ if (ret)
+ goto out_clear_configs;
+
+ ret = resctrl_arch_update_domains(r, io_alloc_closid);
+
+out_clear_configs:
+ rdt_staged_configs_clear();
+out_unlock:
+ mutex_unlock(&rdtgroup_mutex);
+ cpus_read_unlock();
+
+ return ret ?: nbytes;
+}
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index a28cc2541475..bab9d9716783 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -440,6 +440,9 @@ ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf,
int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, struct seq_file *seq,
void *v);
+ssize_t resctrl_io_alloc_cbm_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off);
+
const char *rdtgroup_name_by_closid(int closid);
#ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 8f40c4a078dd..236b6e49761a 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1973,9 +1973,10 @@ static struct rftype res_common_files[] = {
},
{
.name = "io_alloc_cbm",
- .mode = 0444,
+ .mode = 0644,
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = resctrl_io_alloc_cbm_show,
+ .write = resctrl_io_alloc_cbm_write,
},
{
.name = "max_threshold_occupancy",
--
2.34.1
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