Re: [PATCH v9 26/26] x86/resctrl: Introduce interface to modify assignment states of the groups

[Reinette Chatre <reinette.chatre@intel.com>]

Hi Babu,

On 10/29/24 4:21 PM, Babu Moger wrote:
> Introduce the interface to assign MBM events in mbm_cntr_assign mode.
> 
> Events can be enabled or disabled by writing to file
> /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> 
> Format is similar to the list format with addition of opcode for the
> assignment operation.
>  "<CTRL_MON group>/<MON group>/<domain_id><opcode><flags>"
> 
> Format for specific type of groups:
> 
>  * Default CTRL_MON group:
>          "//<domain_id><opcode><flags>"
> 
>  * Non-default CTRL_MON group:
>          "<CTRL_MON group>//<domain_id><opcode><flags>"
> 
>  * Child MON group of default CTRL_MON group:
>          "/<MON group>/<domain_id><opcode><flags>"
> 
>  * Child MON group of non-default CTRL_MON group:
>          "<CTRL_MON group>/<MON group>/<domain_id><opcode><flags>"
> 
> Domain_id '*' will apply the flags on all the domains.
> 
> Opcode can be one of the following:
> 
>  = Update the assignment to match the flags
>  + Assign a new MBM event without impacting existing assignments.
>  - Unassign a MBM event from currently assigned events.
> 
> Assignment flags can be one of the following:
>  t  MBM total event
>  l  MBM local event
>  tl Both total and local MBM events
>  _  None of the MBM events. Valid only with '=' opcode. This flag cannot
>     be combined with other flags.
> 
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
> v9: Fixed handling special case '//0=' and '//".
>     Removed extra strstr() call.
>     Added generic failure text when assignment operation fails.
>     Corrected user documentation format texts.
> 
> v8: Moved unassign as the first action during the assign modification.
>     Assign none "_" takes priority. Cannot be mixed with other flags.
>     Updated the documentation and .rst file format. htmldoc looks ok.
> 
> v7: Simplified the parsing (strsep(&token, "//") in rdtgroup_mbm_assign_control_write().
>     Added mutex lock in rdtgroup_mbm_assign_control_write() while processing.
>     Renamed rdtgroup_find_grp to rdtgroup_find_grp_by_name.
>     Fixed rdtgroup_str_to_mon_state to return error for invalid flags.
>     Simplified the calls rdtgroup_assign_cntr by merging few functions earlier.
>     Removed ABMC reference in FS code.
>     Reinette commented about handling the combination of flags like 'lt_' and '_lt'.
>     Not sure if we need to change the behaviour here. Processed them sequencially right now.
>     Users have the liberty to pass the flags. Restricting it might be a problem later.
> 
> v6: Added support assign all if domain id is '*'
>     Fixed the allocation of counter id if it not assigned already.
> 
> v5: Interface name changed from mbm_assign_control to mbm_control.
>     Fixed opcode and flags combination.
>     '=_" is valid.
>     "-_" amd "+_" is not valid.
>     Minor message update.
>     Renamed the function with prefix - rdtgroup_.
>     Corrected few documentation mistakes.
>     Rebase related changes after SNC support.
> 
> v4: Added domain specific assignments. Fixed the opcode parsing.
> 
> v3: New patch.
>     Addresses the feedback to provide the global assignment interface.
>     https://lore.kernel.org/lkml/c73f444b-83a1-4e9a-95d3-54c5165ee782@intel.com/
> ---
>  Documentation/arch/x86/resctrl.rst     | 116 +++++++++++-
>  arch/x86/kernel/cpu/resctrl/internal.h |  10 ++
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 236 ++++++++++++++++++++++++-
>  3 files changed, 360 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index 590727bec44b..d0a107d251ec 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -347,7 +347,8 @@ with the following files:
>  	 t  MBM total event is assigned.
>  	 l  MBM local event is assigned.
>  	 tl Both MBM total and local events are assigned.
> -	 _  None of the MBM events are assigned.
> +	 _  None of the MBM events are assigned. Only works with opcode '=' for write
> +	    and cannot be combined with other flags.
>  
>  	Examples:
>  	::
> @@ -365,6 +366,119 @@ with the following files:
>  	There are four resctrl groups. All the groups have total and local MBM events
>  	assigned on domain 0 and 1.
>  
> +	Assignment state can be updated by writing to the interface.

This is already a bit far from original definition so it may help to be specific what is
meant with "the interface". For example,

	Assignment state can be updated by writing to "mbm_assign_control".

> +
> +	Format is similar to the list format with addition of opcode for the
> +	assignment operation.
> +
> +		"<CTRL_MON group>/<MON group>/<domain_id><opcode><flags>"
> +
> +	Format for each type of groups:

"Format for each type of group"  or "Format of each type of group"?

> +
> +        * Default CTRL_MON group:
> +                "//<domain_id><opcode><flags>"
> +
> +        * Non-default CTRL_MON group:
> +                "<CTRL_MON group>//<domain_id><opcode><flags>"
> +
> +        * Child MON group of default CTRL_MON group:
> +                "/<MON group>/<domain_id><opcode><flags>"
> +
> +        * Child MON group of non-default CTRL_MON group:
> +                "<CTRL_MON group>/<MON group>/<domain_id><opcode><flags>"
> +
> +	Domain_id '*' will apply the flags on all the domains.

"apply the flags on all the domains" -> "apply the flags to all the domains"?

> +
> +	Opcode can be one of the following:
> +	::
> +
> +	 = Update the assignment to match the MBM event.
> +	 + Assign a new MBM event without impacting existing assignments.
> +	 - Unassign a MBM event from currently assigned events.
> +
> +	Examples:
> +	Initial group status:
> +	::
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +	  non_default_ctrl_mon_grp//0=tl;1=tl;
> +	  non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=tl;
> +	  //0=tl;1=tl;
> +	  /child_default_mon_grp/0=tl;1=tl;
> +
> +	To update the default group to assign only total MBM event on domain 0:
> +	::
> +
> +	  # echo "//0=t" > /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +
> +	Assignment status after the update:
> +	::
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +	  non_default_ctrl_mon_grp//0=tl;1=tl;
> +	  non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=tl;
> +	  //0=t;1=tl;
> +	  /child_default_mon_grp/0=tl;1=tl;
> +
> +	To update the MON group child_default_mon_grp to remove total MBM event on domain 1:
> +	::
> +
> +	  # echo "/child_default_mon_grp/1-t" > /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +
> +	Assignment status after the update:
> +	::
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +	  non_default_ctrl_mon_grp//0=tl;1=tl;
> +	  non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=tl;
> +	  //0=t;1=tl;
> +	  /child_default_mon_grp/0=tl;1=l;
> +
> +	To update the MON group non_default_ctrl_mon_grp/child_non_default_mon_grp to unassign
> +	both local and total MBM events on domain 1:
> +	::
> +
> +	  # echo "non_default_ctrl_mon_grp/child_non_default_mon_grp/1=_" >
> +			/sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +
> +	Assignment status after the update:
> +	::
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +	  non_default_ctrl_mon_grp//0=tl;1=tl;
> +	  non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=_;
> +	  //0=t;1=tl;
> +	  /child_default_mon_grp/0=tl;1=l;
> +
> +	To update the default group to add a local MBM event domain 0.

"." -> ":"

> +	::
> +
> +	  # echo "//0+l" > /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +
> +	Assignment status after the update:
> +	::
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +	  non_default_ctrl_mon_grp//0=tl;1=tl;
> +	  non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=_;
> +	  //0=tl;1=tl;
> +	  /child_default_mon_grp/0=tl;1=l;
> +
> +	To update the non default CTRL_MON group non_default_ctrl_mon_grp to unassign all the
> +	MBM events on all the domains.

"." -> ":"

> +	::
> +
> +	  # echo "non_default_ctrl_mon_grp//*=_" > /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +
> +	Assignment status after the update:
> +	::
> +
> +	  # cat /sys/fs/resctrl/info/L3_MON/mbm_assign_control
> +	  non_default_ctrl_mon_grp//0=_;1=_;
> +	  non_default_ctrl_mon_grp/child_non_default_mon_grp/0=tl;1=_;
> +	  //0=tl;1=tl;
> +	  /child_default_mon_grp/0=tl;1=l;
> +
>  "max_threshold_occupancy":
>  		Read/write file provides the largest value (in
>  		bytes) at which a previously used LLC_occupancy
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index b90d8c90b4b6..3ccaea6a2803 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -74,6 +74,16 @@
>   */
>  #define MBM_EVENT_ARRAY_INDEX(_event) ((_event) - 2)
>  
> +/*
> + * Assignment flags for mbm_cntr_assign feature
> + */

"mbm_cntr_assign feature" -> "mbm_cntr_assign mode"?

> +enum {
> +	ASSIGN_NONE	= 0,
> +	ASSIGN_TOTAL	= BIT(QOS_L3_MBM_TOTAL_EVENT_ID),
> +	ASSIGN_LOCAL	= BIT(QOS_L3_MBM_LOCAL_EVENT_ID),
> +	ASSIGN_INVALID,
> +};
> +
>  /**
>   * cpumask_any_housekeeping() - Choose any CPU in @mask, preferring those that
>   *			        aren't marked nohz_full
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 5cc40eacbe85..9fe419d0c536 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1082,6 +1082,239 @@ static int rdtgroup_mbm_assign_control_show(struct kernfs_open_file *of,
>  	return 0;
>  }
>  
> +static int rdtgroup_str_to_mon_state(char *flag)

It seems strange to me that a variable used to contain flag bits
is of type int. Why is it not unsigned?

> +{
> +	int i, mon_state = ASSIGN_NONE;
> +
> +	if (!strlen(flag))
> +		return ASSIGN_INVALID;
> +
> +	for (i = 0; i < strlen(flag); i++) {
> +		switch (*(flag + i)) {
> +		case 't':
> +			mon_state |= ASSIGN_TOTAL;
> +			break;
> +		case 'l':
> +			mon_state |= ASSIGN_LOCAL;
> +			break;
> +		case '_':
> +			return ASSIGN_NONE;
> +		default:
> +			return ASSIGN_INVALID;
> +		}
> +	}
> +
> +	return mon_state;
> +}
> +
> +static struct rdtgroup *rdtgroup_find_grp_by_name(enum rdt_group_type rtype,
> +						  char *p_grp, char *c_grp)
> +{
> +	struct rdtgroup *rdtg, *crg;
> +
> +	if (rtype == RDTCTRL_GROUP && *p_grp == '\0') {
> +		return &rdtgroup_default;
> +	} else if (rtype == RDTCTRL_GROUP) {
> +		list_for_each_entry(rdtg, &rdt_all_groups, rdtgroup_list)
> +			if (!strcmp(p_grp, rdtg->kn->name))
> +				return rdtg;
> +	} else if (rtype == RDTMON_GROUP) {
> +		list_for_each_entry(rdtg, &rdt_all_groups, rdtgroup_list) {
> +			if (!strcmp(p_grp, rdtg->kn->name)) {
> +				list_for_each_entry(crg, &rdtg->mon.crdtgrp_list,
> +						    mon.crdtgrp_list) {
> +					if (!strcmp(c_grp, crg->kn->name))
> +						return crg;
> +				}
> +			}
> +		}
> +	}
> +
> +	return NULL;
> +}
> +
> +static int rdtgroup_process_flags(struct rdt_resource *r,
> +				  enum rdt_group_type rtype,
> +				  char *p_grp, char *c_grp, char *tok)
> +{
> +	int op, mon_state, assign_state, unassign_state;

Same comment about type ... these *_state variables are used to contain
bits representing the flags of the various states. An unsigned variable
seems more appropriate.

> +	char *dom_str, *id_str, *op_str;
> +	struct rdt_mon_domain *d;
> +	struct rdtgroup *rdtgrp;
> +	unsigned long dom_id;
> +	int ret, found = 0;

Could found be boolean?

> +
> +	rdtgrp = rdtgroup_find_grp_by_name(rtype, p_grp, c_grp);
> +
> +	if (!rdtgrp) {
> +		rdt_last_cmd_puts("Not a valid resctrl group\n");
> +		return -EINVAL;
> +	}
> +
> +next:
> +	if (!tok || tok[0] == '\0')
> +		return 0;
> +
> +	/* Start processing the strings for each domain */
> +	dom_str = strim(strsep(&tok, ";"));
> +
> +	op_str = strpbrk(dom_str, "=+-");
> +
> +	if (op_str) {
> +		op = *op_str;
> +	} else {
> +		rdt_last_cmd_puts("Missing operation =, +, - character\n");
> +		return -EINVAL;
> +	}
> +
> +	id_str = strsep(&dom_str, "=+-");
> +
> +	/* Check for domain id '*' which means all domains */
> +	if (id_str && *id_str == '*') {
> +		d = NULL;
> +		goto check_state;
> +	} else if (!id_str || kstrtoul(id_str, 10, &dom_id)) {
> +		rdt_last_cmd_puts("Missing domain id\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Verify if the dom_id is valid */
> +	list_for_each_entry(d, &r->mon_domains, hdr.list) {
> +		if (d->hdr.id == dom_id) {
> +			found = 1;
> +			break;
> +		}
> +	}
> +
> +	if (!found) {
> +		rdt_last_cmd_printf("Invalid domain id %ld\n", dom_id);
> +		return -EINVAL;
> +	}

I am missing how "found" is handled on second iteration. If an invalid domain
follows a valid domain it seems like "found" remains set from previous iteration?

> +
> +check_state:
> +	mon_state = rdtgroup_str_to_mon_state(dom_str);
> +
> +	if (mon_state == ASSIGN_INVALID) {
> +		rdt_last_cmd_puts("Invalid assign flag\n");
> +		goto out_fail;
> +	}
> +
> +	assign_state = 0;
> +	unassign_state = 0;
> +
> +	switch (op) {
> +	case '+':
> +		if (mon_state == ASSIGN_NONE) {
> +			rdt_last_cmd_puts("Invalid assign opcode\n");
> +			goto out_fail;
> +		}
> +		assign_state = mon_state;
> +		break;
> +	case '-':
> +		if (mon_state == ASSIGN_NONE) {
> +			rdt_last_cmd_puts("Invalid assign opcode\n");
> +			goto out_fail;
> +		}
> +		unassign_state = mon_state;
> +		break;
> +	case '=':
> +		assign_state = mon_state;
> +		unassign_state = (ASSIGN_TOTAL | ASSIGN_LOCAL) & ~assign_state;
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	if (unassign_state & ASSIGN_TOTAL) {
> +		ret = rdtgroup_unassign_cntr_event(r, rdtgrp, d, QOS_L3_MBM_TOTAL_EVENT_ID);
> +		if (ret)
> +			goto out_fail;
> +	}
> +
> +	if (unassign_state & ASSIGN_LOCAL) {
> +		ret = rdtgroup_unassign_cntr_event(r, rdtgrp, d, QOS_L3_MBM_LOCAL_EVENT_ID);
> +		if (ret)
> +			goto out_fail;
> +	}
> +
> +	if (assign_state & ASSIGN_TOTAL) {
> +		ret = rdtgroup_assign_cntr_event(r, rdtgrp, d, QOS_L3_MBM_TOTAL_EVENT_ID);
> +		if (ret)
> +			goto out_fail;
> +	}
> +
> +	if (assign_state & ASSIGN_LOCAL) {
> +		ret = rdtgroup_assign_cntr_event(r, rdtgrp, d, QOS_L3_MBM_LOCAL_EVENT_ID);
> +		if (ret)
> +			goto out_fail;
> +	}
> +
> +	goto next;
> +
> +out_fail:
> +	rdt_last_cmd_printf("Assign operation '%c%s' failed on the group %s/%s/\n",
> +			    op, dom_str, p_grp, c_grp);
> +

Can the domain id be printed also? This seems only piece missing to understand what failed.

> +	return -EINVAL;
> +}
> +
> +static ssize_t rdtgroup_mbm_assign_control_write(struct kernfs_open_file *of,
> +						 char *buf, size_t nbytes, loff_t off)
> +{
> +	struct rdt_resource *r = of->kn->parent->priv;
> +	char *token, *cmon_grp, *mon_grp;
> +	enum rdt_group_type rtype;
> +	int ret;
> +
> +	/* 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 (!resctrl_arch_mbm_cntr_assign_enabled(r)) {
> +		rdt_last_cmd_puts("mbm_cntr_assign mode is not enabled\n");
> +		mutex_unlock(&rdtgroup_mutex);
> +		cpus_read_unlock();
> +		return -EINVAL;
> +	}
> +
> +	while ((token = strsep(&buf, "\n")) != NULL) {
> +		/*
> +		 * The write command follows the following format:
> +		 * “<CTRL_MON group>/<MON group>/<domain_id><opcode><flags>”
> +		 * Extract the CTRL_MON group.
> +		 */
> +		cmon_grp = strsep(&token, "/");
> +
> +		/*
> +		 * Extract the MON_GROUP.
> +		 * strsep returns empty string for contiguous delimiters.
> +		 * Empty mon_grp here means it is a RDTCTRL_GROUP.
> +		 */
> +		mon_grp = strsep(&token, "/");
> +
> +		if (*mon_grp == '\0')
> +			rtype = RDTCTRL_GROUP;
> +		else
> +			rtype = RDTMON_GROUP;
> +
> +		ret = rdtgroup_process_flags(r, rtype, cmon_grp, mon_grp, token);
> +		if (ret)
> +			break;
> +	}
> +
> +	mutex_unlock(&rdtgroup_mutex);
> +	cpus_read_unlock();
> +
> +	return ret ?: nbytes;
> +}
> +
>  #ifdef CONFIG_PROC_CPU_RESCTRL
>  
>  /*
> @@ -2383,9 +2616,10 @@ static struct rftype res_common_files[] = {
>  	},
>  	{
>  		.name		= "mbm_assign_control",
> -		.mode		= 0444,
> +		.mode		= 0644,
>  		.kf_ops		= &rdtgroup_kf_single_ops,
>  		.seq_show	= rdtgroup_mbm_assign_control_show,
> +		.write		= rdtgroup_mbm_assign_control_write,
>  	},
>  	{
>  		.name		= "mbm_assign_mode",

Reinette