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Message-ID: <176382651370.498.7261884444268596925.tip-bot2@tip-bot2>
Date: Sat, 22 Nov 2025 15:48:20 -0000
From: "tip-bot2 for Babu Moger" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Babu Moger <babu.moger@....com>, "Borislav Petkov (AMD)" <bp@...en8.de>,
Reinette Chatre <reinette.chatre@...el.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/cache] fs/resctrl: Introduce interface to modify io_alloc
capacity bitmasks
The following commit has been merged into the x86/cache branch of tip:
Commit-ID: 28fa2cce7a8388f09e457f1e24241ca6d5e985d8
Gitweb: https://git.kernel.org/tip/28fa2cce7a8388f09e457f1e24241ca6d5e985d8
Author: Babu Moger <babu.moger@....com>
AuthorDate: Wed, 12 Nov 2025 18:57:35 -06:00
Committer: Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Sat, 22 Nov 2025 14:28:31 +01:00
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>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
Link: https://patch.msgid.link/67609641b03ccfba18a8ee0bf9dbd1f3dcbecda3.1762995456.git.babu.moger@amd.com
---
Documentation/filesystems/resctrl.rst | 12 +++-
fs/resctrl/ctrlmondata.c | 93 ++++++++++++++++++++++++++-
fs/resctrl/internal.h | 2 +-
fs/resctrl/rdtgroup.c | 3 +-
4 files changed, 109 insertions(+), 1 deletion(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index e799453..bbc4b6c 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -196,6 +196,18 @@ 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 c43bede..332918f 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -864,3 +864,96 @@ out_unlock:
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 779a575..e1eda74 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -440,6 +440,8 @@ ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf,
const char *rdtgroup_name_by_closid(u32 closid);
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);
#ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index ac326db..3614974 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",
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