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Message-ID: <82045638-2b26-4682-9374-1c3e400a580a@intel.com>
Date: Mon, 21 Jul 2025 20:32:55 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
<Dave.Martin@....com>, <james.morse@....com>, <tglx@...utronix.de>,
<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <akpm@...ux-foundation.org>,
<paulmck@...nel.org>, <rostedt@...dmis.org>, <Neeraj.Upadhyay@....com>,
<david@...hat.com>, <arnd@...db.de>, <fvdl@...gle.com>, <seanjc@...gle.com>,
<thomas.lendacky@....com>, <pawan.kumar.gupta@...ux.intel.com>,
<yosry.ahmed@...ux.dev>, <sohil.mehta@...el.com>, <xin@...or.com>,
<kai.huang@...el.com>, <xiaoyao.li@...el.com>, <peterz@...radead.org>,
<me@...aill.net>, <mario.limonciello@....com>, <xin3.li@...el.com>,
<ebiggers@...gle.com>, <ak@...ux.intel.com>, <chang.seok.bae@...el.com>,
<andrew.cooper3@...rix.com>, <perry.yuan@....com>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 10/10] fs/resctrl: Introduce interface to modify
io_alloc Capacity Bit Masks
Hi Babu,
On 7/10/25 10:16 AM, Babu Moger wrote:
> "io_alloc" feature enables direct insertion of data from I/O devices into
> the cache. By directly caching data from I/O devices rather than first
> storing the I/O data in DRAM, it reduces the demands on DRAM bandwidth and
> reduces latency to the processor consuming the I/O data.
>
> Provide the interface to modify io_alloc CBMs (Capacity Bit Mask) when
"Provide the interface to modify io_alloc CBMs (Capacity Bit Mask) when feature is
enabled." ->
"Enable users to modify io_alloc CBMs (Capacity Bit Masks) via the io_alloc_cbm
resctrl file when io_alloc is enabled."?
> feature is enabled. Update the CBMs for both CDP_DATA and CDP_CODE when CDP
> is enabled.
>
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
...
> ---
> Documentation/filesystems/resctrl.rst | 8 ++
> fs/resctrl/ctrlmondata.c | 4 +-
> fs/resctrl/internal.h | 2 +
> fs/resctrl/rdtgroup.c | 112 +++++++++++++++++++++++++-
> 4 files changed, 123 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index c22a9dd667cd..b9c3ffdec27f 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -189,6 +189,14 @@ 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
> +
> When CDP is enabled "io_alloc_cbm" associated with the DATA and 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 5c16557fb7a8..23c72a5ac043 100644
> --- a/fs/resctrl/ctrlmondata.c
> +++ b/fs/resctrl/ctrlmondata.c
> @@ -148,8 +148,8 @@ static bool cbm_validate(char *buf, u32 *data, struct rdt_resource *r)
> * 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)
> +int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s,
> + struct rdt_ctrl_domain *d)
This can remain static by moving caller to ctrlmondata.c
> {
> enum rdtgrp_mode mode = data->mode;
> struct resctrl_staged_config *cfg;
> diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
> index ab76a1e2e679..011564e69ed5 100644
> --- a/fs/resctrl/internal.h
> +++ b/fs/resctrl/internal.h
> @@ -382,6 +382,8 @@ bool closid_allocated(unsigned int closid);
> int resctrl_find_cleanest_closid(void);
> void show_doms(struct seq_file *s, struct resctrl_schema *schema,
> char *name, int closid);
> +int parse_cbm(struct rdt_parse_data *data, struct resctrl_schema *s,
> + struct rdt_ctrl_domain *d);
>
> #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 008657e43656..1093ec5e385b 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -2036,6 +2036,115 @@ static int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of,
> return ret;
> }
>
> +static int resctrl_io_alloc_parse_line(char *line, struct rdt_resource *r,
> + struct resctrl_schema *s, u32 closid)
Please move to ctrlmondata.c
> +{
> + 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;
> + goto next;
> + }
> + }
> + return -EINVAL;
> +}
> +
> +static ssize_t resctrl_io_alloc_cbm_write(struct kernfs_open_file *of,
> + char *buf, size_t nbytes, loff_t off)
Please move to ctrlmondata.c
> +{
> + struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
> + enum resctrl_conf_type peer_type;
> + struct rdt_resource *r = s->res;
> + struct resctrl_schema *peer_s;
> + u32 io_alloc_closid;
> + char *peer_buf;
> + 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);
> +
> + if (!r->cache.io_alloc_capable) {
> + rdt_last_cmd_printf("io_alloc is not supported on %s\n", s->name);
rdt_last_cmd_clear() is required before any write to the buffer.
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> + rdt_last_cmd_clear();
> + rdt_staged_configs_clear();
> +
> + if (!resctrl_arch_get_io_alloc_enabled(r)) {
> + rdt_last_cmd_printf("io_alloc is not enabled on %s\n", s->name);
> + ret = -EINVAL;
Inconsistent error codes when io_alloc is not enabled. resctrl_io_alloc_write()
and resctrl_io_alloc_cbm_show() returns -ENODEV.
> + goto out_unlock;
> + }
> +
> + io_alloc_closid = resctrl_io_alloc_closid(r);
> +
> + /*
> + * When CDP is enabled, update the schema for both CDP_DATA and CDP_CODE.
> + * Since the buffer is altered during parsing, create a copy to handle
> + * peer schemata separately.
> + */
> + if (resctrl_arch_get_cdp_enabled(r->rid)) {
> + peer_type = resctrl_peer_type(s->conf_type);
> + peer_s = resctrl_get_schema(peer_type);
> + peer_buf = kmalloc(nbytes, GFP_KERNEL);
> + if (!peer_buf) {
> + rdt_last_cmd_puts("Out of Memory - io_alloc update failed\n");
> + ret = -ENOMEM;
> + goto out_unlock;
> + }
> +
> + memcpy(peer_buf, buf, nbytes);
> +
> + if (peer_s)
> + ret = resctrl_io_alloc_parse_line(peer_buf, r, peer_s, io_alloc_closid);
Similar to resctrl_io_alloc_write() this looks unnecessary. I think this can be simplified
by moving the CDP check to resctrl_io_alloc_parse_line() where the provided CBM can be parsed
*once* and the staged config of a CDP type just copied to the staged config of its peer type.
> +
> + kfree(peer_buf);
> + }
> +
> + if (!ret)
> + ret = resctrl_io_alloc_parse_line(buf, r, s, io_alloc_closid);
> +
> + if (ret)
> + goto out_unlock;
> +
> + ret = resctrl_arch_update_domains(r, io_alloc_closid);
> +
> +out_unlock:
> + rdt_staged_configs_clear();
> + mutex_unlock(&rdtgroup_mutex);
> + cpus_read_unlock();
> +
> + return ret ?: nbytes;
> +}
> +
> /* rdtgroup information files for one cache resource. */
> static struct rftype res_common_files[] = {
> {
> @@ -2135,9 +2244,10 @@ 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",
Reinette
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