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Message-ID: <45384d5f-a6e7-4a82-974d-84e189381b36@intel.com>
Date: Mon, 18 Nov 2024 13:51:36 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tglx@...utronix.de>,
<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <fenghua.yu@...el.com>, <x86@...nel.org>, <hpa@...or.com>,
<thuth@...hat.com>, <paulmck@...nel.org>, <rostedt@...dmis.org>,
<akpm@...ux-foundation.org>, <xiongwei.song@...driver.com>,
<pawan.kumar.gupta@...ux.intel.com>, <daniel.sneddon@...ux.intel.com>,
<perry.yuan@....com>, <sandipan.das@....com>, <kai.huang@...el.com>,
<xiaoyao.li@...el.com>, <seanjc@...gle.com>, <jithu.joseph@...el.com>,
<brijesh.singh@....com>, <xin3.li@...el.com>, <ebiggers@...gle.com>,
<andrew.cooper3@...rix.com>, <mario.limonciello@....com>,
<james.morse@....com>, <tan.shaopeng@...itsu.com>, <tony.luck@...el.com>,
<vikas.shivappa@...ux.intel.com>, <linux-doc@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <peternewman@...gle.com>,
<maciej.wieczor-retman@...el.com>, <eranian@...gle.com>,
<jpoimboe@...nel.org>, <thomas.lendacky@....com>
Subject: Re: [PATCH v9 26/26] x86/resctrl: Introduce interface to modify
assignment states of the groups
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@....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
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