"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
feature is enabled. Update the CBMs for both CDP_DATA and CDP_CODE when CDP
is enabled.

Signed-off-by: Babu Moger <babu.moger@amd.com>
---
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 |   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)
 {
 	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)
+{
+	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)
+{
+	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);
+		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;
+		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);
+
+		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",
-- 
2.34.1

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@amd.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

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@amd.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