Re: [PATCH v5 20/20] x86/resctrl: Introduce interface to modify assignment states of the groups

[Reinette Chatre]

Hi Babu,

On 7/3/24 2:48 PM, Babu Moger wrote:
> Introduce the interface to enable events in ABMC mode.

As mentioned in cover letter, please take care with terms. This
interface does not "enable events" - note that events can be
"enabled" even in legacy mode. This is the interface to
assign counters.

> 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 op-code for the
> assignment operation.
>   "<CTRL_MON group>/<MON group>/<op-code><flags>"

Missing a "domain_id".

> Format for specific type of groups:
>
>   * Default CTRL_MON group:
>           "//<domain_id><op-code><flags>"
>
>   * Non-default CTRL_MON group:
>           "<CTRL_MON group>//<domain_id><op-code><flags>"
>
>   * Child MON group of default CTRL_MON group:
>           "/<MON group>/<domain_id><op-code><flags>"
>
>   * Child MON group of non-default CTRL_MON group:
>           "<CTRL_MON group>/<MON group>/<domain_id><op-code><flags>"
>
> Op-code can be one of the following:
>
>   = Update the assignment to match the flags
>   + enable a new state
>   - disable a new state

(note comment in cover letter about consistent terms)

> Assignment flags can be one of the following:
>   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. Valid only with '=" opcode.
>
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> ---
> 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@xxxxxxxxx/
> ---
>   Documentation/arch/x86/resctrl.rst     |  81 +++++++-
>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 250 ++++++++++++++++++++++++-
>   2 files changed, 329 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
> index 05fee779e109..5a621235eb2b 100644
> --- a/Documentation/arch/x86/resctrl.rst
> +++ b/Documentation/arch/x86/resctrl.rst
> @@ -331,7 +331,7 @@ 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:
>   	::
> @@ -358,6 +358,85 @@ with the following files:
>   
>   	 /child_default_mon_grp/ - This is a child monitor group of default CTRL_MON group.
>   
> +	Assignment state can be updated by writing to the interface.
> +
> +	Format is similar to the list format with addition of op-code for the
> +	assignment operation.
> +
> +		"<CTRL_MON group>/<MON group>/<op-code><flags>"

Missing domain_id

> +
> +	Format for each type of groups:
> +
> +        * Default CTRL_MON group:
> +                "//<domain_id><op-code><flags>"
> +
> +        * Non-default CTRL_MON group:
> +                "<CTRL_MON group>//<domain_id><op-code><flags>"
> +
> +        * Child MON group of default CTRL_MON group:
> +                "/<MON group>/<domain_id><op-code><flags>"
> +
> +        * Child MON group of non-default CTRL_MON group:
> +                "<CTRL_MON group>/<MON group>/<domain_id><op-code><flags>"
> +
> +	Op-code can be one of the following:
> +	::
> +
> +	 = Update the assignment to match the flags.
> +	 + Add a new state.
> +	 - delete a new state.
> +
> +	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 enable only total 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 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
> +	  remove both local and total 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 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;
> +
>   "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/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 0de9f23d5389..84c0874d7872 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1068,6 +1068,253 @@ static int rdtgroup_mbm_control_show(struct kernfs_open_file *of,
>   	return 0;
>   }
>   
> +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;
> +		default:
> +			mon_state = ASSIGN_NONE;
> +			break;
> +		}
> +	}
> +

No. As I mentioned before this makes all this work for nothing
by preventing us from ever adding another flag. Please do not
have a default catchall that unassigns all flags.

> +	return mon_state;
> +}
> +
> +static struct rdtgroup *rdtgroup_find_grp(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(enum rdt_group_type rtype, char *p_grp, char *c_grp, char *tok)
> +{
> +	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> +	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, "=+-");
> +
> +	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;
> +	}
> +
> +	mon_state = rdtgroup_str_to_mon_state(dom_str);
> +
> +	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;
> +	}
> +

this flow is not clear to me ... I see how an existing counter is
configured but I do not see any counter being freed/allocated, where is that
done?

> +	if (assign_state & ASSIGN_TOTAL)
> +		ret = resctrl_arch_assign_cntr(d, QOS_L3_MBM_TOTAL_EVENT_ID,
> +					       rdtgrp->mon.rmid,
> +					       rdtgrp->mon.cntr_id[0],
> +					       rdtgrp->closid, 1);
> +	if (ret)
> +		goto out_fail;
> +
> +	if (assign_state & ASSIGN_LOCAL)
> +		ret = resctrl_arch_assign_cntr(d, QOS_L3_MBM_LOCAL_EVENT_ID,
> +					       rdtgrp->mon.rmid,
> +					       rdtgrp->mon.cntr_id[1],
> +					       rdtgrp->closid, 1);
> +
> +	if (ret)
> +		goto out_fail;
> +
> +	if (unassign_state & ASSIGN_TOTAL)
> +		ret = resctrl_arch_assign_cntr(d, QOS_L3_MBM_TOTAL_EVENT_ID,
> +					       rdtgrp->mon.rmid,
> +					       rdtgrp->mon.cntr_id[0],
> +					       rdtgrp->closid, 0);
> +
> +	if (ret)
> +		goto out_fail;
> +
> +	if (unassign_state & ASSIGN_LOCAL)
> +		ret = resctrl_arch_assign_cntr(d, QOS_L3_MBM_LOCAL_EVENT_ID,
> +					       rdtgrp->mon.rmid,
> +					       rdtgrp->mon.cntr_id[1],
> +					       rdtgrp->closid, 0);
> +	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;
> +	struct rdt_hw_resource *hw_res;
> +	int ret;
> +
> +	hw_res = resctrl_to_arch_res(r);
> +	if (!hw_res->abmc_enabled)
> +		return -EINVAL;
> +
> +	/* Valid input requires a trailing newline */
> +	if (nbytes == 0 || buf[nbytes - 1] != '\n')
> +		return -EINVAL;
> +
> +	buf[nbytes - 1] = '\0';
> +	rdt_last_cmd_clear();

rdt_last_cmd_clear() should be called with mutex held

> +
> +	cpus_read_lock();
> +	mutex_lock(&rdtgroup_mutex);
> +
> +	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 consicutive delimiters and

consicutive -> consecutive

> +			 * 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(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, "/");
> +
> +			/* 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(RDTMON_GROUP, cmon_grp, mon_grp, token);
> +			if (ret)
> +				break;
> +		}

can these two blocks not be merged? strsep(&token, "//") and strsep(&token, "/") do the same
thing, no?

> +	}
> +
> +	mutex_unlock(&rdtgroup_mutex);
> +	cpus_read_unlock();
> +
> +	return ret ?: nbytes;
> +}
> +
>   #ifdef CONFIG_PROC_CPU_RESCTRL
>   
>   /*
> @@ -2282,9 +2529,10 @@ 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