Message-ID: <ecf340f9-a7d0-4ac7-ab1b-4ce4a17a9d20@amd.com>
Date: Mon, 4 Aug 2025 16:01:31 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.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 Reinette,

On 7/21/25 22:32, Reinette Chatre wrote:
> 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."?

Sure.

> 
>> 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

Yes.

> 
>>  {
>>  	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

Yes.

> 
>> +{
>> +	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

Yes.

> 
>> +{
>> +	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.

Added now.

> 
>> +		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.

Changed it to -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.

Yes. Changed it now.

> 
>> +
>> +		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
> 

-- 
Thanks
Babu Moger

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