Message-ID: <32348c71-06f5-435e-88b8-14267a20571e@amd.com>
Date: Wed, 17 Jul 2024 11:22:50 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.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 v5 20/20] x86/resctrl: Introduce interface to modify
 assignment states of the groups

Hi Reinette,

On 7/12/24 17:17, Reinette Chatre wrote:
> 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".

Yea. Will fix it.

> 
>>
>> 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)

Sure.
> 
>>
>> 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@....com>
>> ---
>> 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     |  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

Sure.

> 
>> +
>> +    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.

Will remove default ASSIGN_NONE.

> 
>> +    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?

My bad. There is a bug here. The following code updates the assignment
states if the group has the counter assigned already.
I need to add the check to allocated/free the counters based on
assign/unassign state requested. Good catch.



> 
>> +    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

Sure.
> 
>> +
>> +    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

Sure.

> 
>> +             * 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?

Sure. Will check.

> 
>> +    }
>> +
>> +    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
> 

-- 
Thanks
Babu Moger

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