Message-ID: <d4873add-ac24-47dd-be45-28af3698c334@intel.com>
Date: Fri, 16 Aug 2024 15:33:35 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <fenghua.yu@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
	<rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
	<yanjiewtw@...il.com>, <kim.phillips@....com>, <lukas.bulwahn@...il.com>,
	<seanjc@...gle.com>, <jmattson@...gle.com>, <leitao@...ian.org>,
	<jpoimboe@...nel.org>, <rick.p.edgecombe@...el.com>,
	<kirill.shutemov@...ux.intel.com>, <jithu.joseph@...el.com>,
	<kai.huang@...el.com>, <kan.liang@...ux.intel.com>,
	<daniel.sneddon@...ux.intel.com>, <pbonzini@...hat.com>,
	<sandipan.das@....com>, <ilpo.jarvinen@...ux.intel.com>,
	<peternewman@...gle.com>, <maciej.wieczor-retman@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>, <james.morse@....com>
Subject: Re: [PATCH v6 22/22] x86/resctrl: Introduce interface to modify
 assignment states of the groups

Hi Babu,

On 8/6/24 3:00 PM, Babu Moger wrote:
> Introduce the interface to assign MBM events in ABMC mode.
> 
> Events can be enabled or disabled by writing to file
> /sys/fs/resctrl/info/L3_MON/mbm_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 MBM event
>   - unassign a MBM event
> 
> 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.

(please note comments in this area of cover letter)

> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
> 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     |  94 +++++++-
>   arch/x86/kernel/cpu/resctrl/internal.h |   7 +
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 315 ++++++++++++++++++++++++-
>   3 files changed, 414 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index 113c22ba6db3..ae3b17b7cefe 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -346,7 +346,7 @@ with the following files:
>   	 t  MBM total event is enabled.
>   	 l  MBM local event is enabled.
>   	 tl Both total and local MBM events are enabled.
> -	 _  None of the MBM events are enabled.
> +	 _  None of the MBM events are enabled. Only works with opcode '=' for write.
>   
>   	Examples:
>   	::
> @@ -365,6 +365,98 @@ with the following files:
>   	 enabled on domain 0 and 1.
>   
>   
> +	Assignment state can be updated by writing to the interface.
> +
> +	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:
> +
> +        * 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 '*' wil apply the flags on all the domains.
> +
> +	Opcode can be one of the following:
> +	::
> +
> +	 = Update the assignment to match the MBM event.
> +	 + Assign a MBM event.

"Assign a new MBM event without impacting existing assignments."?

> +	 - Unassign a MBM event.

(similar)

> +
> +	Examples:
> +	::
> +
> +	  Initial group status:
> +	  # cat /sys/fs/resctrl/info/L3_MON/mbm_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_control
> +
> +	  Assignment status after the update:
> +	  # cat /sys/fs/resctrl/info/L3_MON/mbm_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_control
> +
> +	  Assignment status after the update:
> +	  $ cat /sys/fs/resctrl/info/L3_MON/mbm_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_control
> +
> +	  Assignment status after the update:
> +	  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_control
> +
> +	  Assignment status after the update:
> +	  # cat /sys/fs/resctrl/info/L3_MON/mbm_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_control
> +
> +	  Assignment status after the update:
> +	  #cat /sys/fs/resctrl/info/L3_MON/mbm_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 ba3012f8f940..5af225b4a497 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -46,6 +46,13 @@
>   
>   #define MON_CNTR_UNSET			U32_MAX
>   
> +/*
> + * Assignment flags for ABMC feature

(this is resctrl fs code)

> + */
> +#define ASSIGN_NONE			0
> +#define ASSIGN_TOTAL			BIT(QOS_L3_MBM_TOTAL_EVENT_ID)
> +#define ASSIGN_LOCAL			BIT(QOS_L3_MBM_LOCAL_EVENT_ID)
> +
>   /**
>    * 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 d7aadca5e4ab..8567fb3a6274 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1034,6 +1034,318 @@ static int rdtgroup_mbm_control_show(struct kernfs_open_file *of,
>   	return 0;
>   }
>   
> +/*
> + * Update the assign states for the domain.
> + *
> + * If this is a new assignment for the group then allocate a counter and update
> + * the assignment else just update the assign state
> + */
> +static int rdtgroup_assign_update(struct rdtgroup *rdtgrp, enum resctrl_event_id evtid,
> +				  struct rdt_mon_domain *d)
> +{
> +	int ret, index;
> +
> +	index = mon_event_config_index_get(evtid);
> +	if (index == INVALID_CONFIG_INDEX)
> +                return -EINVAL;

(wrong spacing ... see checkpatch.pl)

> +
> +	if (rdtgrp->mon.cntr_id[index] == MON_CNTR_UNSET) {
> +		ret = rdtgroup_alloc_cntr(rdtgrp, index);
> +		if (ret < 0)
> +			goto out_done;
> +	}
> +
> +	/* Update the state on all domains if d == NULL */
> +	if (d == NULL) {

if (!d) ... (checkpatch)

> +		ret = rdtgroup_assign_cntr(rdtgrp, evtid);
> +	} else {
> +		ret = resctrl_arch_assign_cntr(d, evtid, rdtgrp->mon.rmid,
> +					       rdtgrp->mon.cntr_id[index],
> +					       rdtgrp->closid, 1);
> +		if (!ret)
> +			set_bit(rdtgrp->mon.cntr_id[index], d->mbm_cntr_map);
> +	}
> +
> +out_done:
> +	return ret;
> +}

Please merge this with almost identical rdtgroup_assign_cntr()

> +
> +/*
> + * Update the unassign state for the domain.
> + *
> + * Free the counter if it is unassigned on all the domains else just
> + * update the unassign state
> + */
> +static int rdtgroup_unassign_update(struct rdtgroup *rdtgrp, enum resctrl_event_id evtid,
> +				    struct rdt_mon_domain *d)
> +{
> +	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> +	int ret = 0, index;
> +
> +	index = mon_event_config_index_get(evtid);
> +	if (index == INVALID_CONFIG_INDEX)
> +                return -EINVAL;

(wrong spacing ... see checkpatch.pl)

> +
> +	if (rdtgrp->mon.cntr_id[index] == MON_CNTR_UNSET)
> +		goto out_done;
> +
> +	if (d == NULL) {

if (!d)

> +		ret = rdtgroup_unassign_cntr(rdtgrp, evtid);
> +	} else {
> +		ret = resctrl_arch_assign_cntr(d, evtid, rdtgrp->mon.rmid,
> +					       rdtgrp->mon.cntr_id[index],
> +					       rdtgrp->closid, 0);
> +		if (!ret) {
> +			clear_bit(rdtgrp->mon.cntr_id[index], d->mbm_cntr_map);
> +			rdtgroup_free_cntr(r, rdtgrp, index);
> +		}
> +	}
> +
> +out_done:
> +	return ret;
> +}

Please merge this with almost identical rdtgroup_unassign_cntr()

> +
> +static int rdtgroup_str_to_mon_state(char *flag)
> +{
> +	int i, mon_state = 0;
> +
> +	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 '_':
> +			mon_state = ASSIGN_NONE;
> +			break;

It looks like this supports flags like "_lt", treating it as assigning
both local and total. I expect this should remove all flags instead?

> +		default:
> +			break;
> +		}
> +	}
> +
> +	return mon_state;
> +}

hmmm ... so you removed assigning mon_state to ASSIGN_NONE from default,
but that did not change what this function returns since ASSIGN_NONE is 0
and mon_state is initialized to 0. Unknown flags should cause error so
that it is possible to add flags in the future. Above prevents us from
ever adding new flags.

> +
> +static struct rdtgroup *rdtgroup_find_grp(enum rdt_group_type rtype, char *p_grp, char *c_grp)

rdtgroup_find_grp() -> rdtgroup_find_grp_by_name()?

> +{
> +	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;
> +	char *dom_str, *id_str, *op_str;
> +	struct rdt_mon_domain *d;
> +	struct rdtgroup *rdtgrp;
> +	unsigned long dom_id;
> +	int ret, found = 0;
> +
> +	rdtgrp = rdtgroup_find_grp(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;
> +	}
> +
> +check_state:
> +	mon_state = rdtgroup_str_to_mon_state(dom_str);

Function should return error and exit here.

> +
> +	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 (assign_state & ASSIGN_TOTAL) {
> +		ret = rdtgroup_assign_update(rdtgrp, QOS_L3_MBM_TOTAL_EVENT_ID, d);
> +		if (ret)
> +			goto out_fail;
> +	}

Should unassign occur before assign so that unassign can make counters available for
assign that follows?

> +
> +	if (assign_state & ASSIGN_LOCAL) {
> +		ret = rdtgroup_assign_update(rdtgrp, QOS_L3_MBM_LOCAL_EVENT_ID, d);
> +		if (ret)
> +			goto out_fail;
> +	}
> +
> +	if (unassign_state & ASSIGN_TOTAL) {
> +		ret = rdtgroup_unassign_update(rdtgrp, QOS_L3_MBM_TOTAL_EVENT_ID, d);
> +		if (ret)
> +			goto out_fail;
> +	}
> +
> +	if (unassign_state & ASSIGN_LOCAL) {
> +		ret = rdtgroup_unassign_update(rdtgrp, QOS_L3_MBM_LOCAL_EVENT_ID, d);
> +		if (ret)
> +			goto out_fail;
> +	}
> +
> +	goto next;
> +
> +out_fail:
> +
> +	return -EINVAL;
> +}
> +
> +static ssize_t rdtgroup_mbm_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;
> +	int ret;
> +
> +	if (!resctrl_arch_get_abmc_enabled())
> +		return -EINVAL;

This needs to be protected by mutex.

> +
> +	/* 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();
> +
> +	while ((token = strsep(&buf, "\n")) != NULL) {
> +		if (strstr(token, "//")) {
> +			/*
> +			 * The CTRL_MON group processing:
> +			 * default CTRL_MON group: "//<flags>"
> +			 * non-default CTRL_MON group: "<CTRL_MON group>//flags"
> +			 * The CTRL_MON group will be empty string if it is a
> +			 * default group.
> +			 */
> +			cmon_grp = strsep(&token, "//");
> +
> +			/*
> +			 * strsep returns empty string for contiguous delimiters.
> +			 * Make sure check for two consecutive delimiters and
> +			 * advance the token.
> +			 */
> +			mon_grp = strsep(&token, "//");
> +			if (*mon_grp != '\0') {
> +				rdt_last_cmd_printf("Invalid CTRL_MON group format %s\n", token);
> +				ret = -EINVAL;
> +				break;
> +			}
> +
> +			ret = rdtgroup_process_flags(r, RDTCTRL_GROUP, cmon_grp, mon_grp, token);
> +			if (ret)
> +				break;
> +		} else if (strstr(token, "/")) {
> +			/*
> +			 * MON group processing:
> +			 * MON_GROUP inside default CTRL_MON group: "/<MON group>/<flags>"
> +			 * MON_GROUP within CTRL_MON group: "<CTRL_MON group>/<MON group>/<flags>"
> +			 */
> +			cmon_grp = strsep(&token, "/");

Isn't strsep(&token, "//") the same as strsep(&token, "/")? It looks like these two big branches
can be merged.

> +
> +			/* Extract the MON_GROUP. It cannot be empty string */
> +			mon_grp = strsep(&token, "/");
> +			if (*mon_grp == '\0') {
> +				rdt_last_cmd_printf("Invalid MON_GROUP format %s\n", token);
> +				ret = -EINVAL;
> +				break;
> +			}
> +
> +			ret = rdtgroup_process_flags(r, RDTMON_GROUP, cmon_grp, mon_grp, token);
> +			if (ret)
> +				break;
> +		}
> +	}
> +
> +	mutex_unlock(&rdtgroup_mutex);
> +	cpus_read_unlock();
> +
> +	return ret ?: nbytes;
> +}
> +
>   #ifdef CONFIG_PROC_CPU_RESCTRL
>   
>   /*
> @@ -2277,9 +2589,10 @@ static struct rftype res_common_files[] = {
>   	},
>   	{
>   		.name		= "mbm_control",
> -		.mode		= 0444,
> +		.mode		= 0644,
>   		.kf_ops		= &rdtgroup_kf_single_ops,
>   		.seq_show	= rdtgroup_mbm_control_show,
> +		.write		= rdtgroup_mbm_control_write,
>   	},
>   	{
>   		.name		= "cpus_list",

Reinette

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