From 28fa2cce7a8388f09e457f1e24241ca6d5e985d8 Mon Sep 17 00:00:00 2001 From: Babu Moger Date: Wed, 12 Nov 2025 18:57:35 -0600 Subject: [PATCH] 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 Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Reinette Chatre 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 e7994538e0cef..bbc4b6cbb71dc 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 c43bedea70d7a..332918fc961a3 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 779a575e08282..e1eda74881a9a 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 ac326db9b5ba0..361497489d875 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", -- 2.47.3