Message-ID: <343960a8-b364-44b1-aebf-ebb7fe0a1466@amd.com>
Date: Thu, 20 Jun 2024 09:46:04 -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 v4 16/19] x86/resctrl: Enable ABMC by default on resctrl
 mount

Hi Reinette,

On 6/13/24 20:50, Reinette Chatre wrote:
> Hi Babu,
> 
> On 5/24/24 5:23 AM, Babu Moger wrote:
>> Enable ABMC by default when feature is supported.
> 
> Why enable/disable it on every mount/unmount cycle though? Why not just
> enable it at the beginning and only change if requested by user?

I think we can do that. This needs to be done at __init
rdt_get_mon_l3_config(). Will let you if i see any issues with that.

> 
>>
>> Counters are assigned automatically on group creation. If the counters
>> are exhausted, report the warnings and continue. It is not required to
>> fail group creation for assignment failures. Users will have the option
>> to modify the assignments.
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>> v4: Few name changes based on the upstream discussion.
>>      Commit message update.
>>
>> v3: This is a new patch. Patch addresses the upstream comment to enable
>>      ABMC feature by default if the feature is available.
>> ---
>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 69 ++++++++++++++++++++++++++
>>   1 file changed, 69 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 5ea1e58c7201..f452b6d9bb99 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -2756,6 +2756,7 @@ static void rdt_disable_ctx(void)
>>   {
>>       resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L3, false);
>>       resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L2, false);
>> +    resctrl_abmc_disable(RDT_RESOURCE_L3);
>>       set_mba_sc(false);
>>         resctrl_debug = false;
>> @@ -2786,6 +2787,8 @@ static int rdt_enable_ctx(struct rdt_fs_context *ctx)
>>       if (ctx->enable_debug)
>>           resctrl_debug = true;
>>   +    resctrl_abmc_enable(RDT_RESOURCE_L3);
>> +
>>       return 0;
>>     out_cdpl3:
>> @@ -2882,6 +2885,41 @@ static void schemata_list_destroy(void)
>>       }
>>   }
>>   +static int resctrl_assign_events(struct rdtgroup *rdtgrp)
>> +{
>> +    struct rdt_resource *r =
>> &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
>> +    struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>> +    int ret = 0;
>> +
>> +    if (!hw_res->abmc_enabled)
>> +        return 0;
> 
> resctrl fs should not be peeking in arch structure

Sure.

> 
>> +
>> +    if (is_mbm_total_enabled())
>> +        ret = resctrl_grp_assign(rdtgrp, QOS_L3_MBM_TOTAL_EVENT_ID);
>> +
>> +    if (!ret && is_mbm_local_enabled())
>> +        ret = resctrl_grp_assign(rdtgrp, QOS_L3_MBM_LOCAL_EVENT_ID);
>> +
> 
> This function needs a comment about why it is ok to return with error and
> partial changes.

Sure.

> 
>> +    return ret;
>> +}
>> +
>> +static int resctrl_unassign_events(struct rdtgroup *rdtgrp)
>> +{
>> +    struct rdt_resource *r =
>> &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
>> +    struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>> +    int ret = 0;
>> +
>> +    if (!hw_res->abmc_enabled)
>> +        return 0;
>> +
>> +    if (is_mbm_total_enabled())
>> +        ret = resctrl_grp_unassign(rdtgrp, QOS_L3_MBM_TOTAL_EVENT_ID);
>> +
>> +    if (!ret && is_mbm_local_enabled())
>> +        ret = resctrl_grp_unassign(rdtgrp, QOS_L3_MBM_LOCAL_EVENT_ID);
>> +    return ret;
>> +}
>> +
>>   static int rdt_get_tree(struct fs_context *fc)
>>   {
>>       struct rdt_fs_context *ctx = rdt_fc2context(fc);
>> @@ -2941,6 +2979,14 @@ static int rdt_get_tree(struct fs_context *fc)
>>           if (ret < 0)
>>               goto out_mongrp;
>>           rdtgroup_default.mon.mon_data_kn = kn_mondata;
>> +
>> +        /*
>> +         * Assign the monitor counters if it is available. If it fails,
>> +         * report the warnings and continue. It is not nessaccery to
>> +         * fail here.
>> +         */
> 
> nessaccery -> necessary

Sure.
> 
> Please elaborate why it is not necessary to fail.

Sure.

> 
> 
>> +        if (resctrl_assign_events(&rdtgroup_default) < 0)
>> +            rdt_last_cmd_puts("Monitor assignment failed\n");
> 
> How will user know that there is a warning? This does not return an error
> so nothing will prompt user to check the status file. Perhaps add a comment
> in the docs to help users at least know that this exists. Another helpful

Sure. Will add text about this in the documentation.

> thing will be to have the counter return "Unassigned" if it has not been
> assigned
> since users familiar with old interface may see "Unavailable" without
> knowing that user action is required to get a working event.

Not so sure about interpreting hardware reported error.

> 
>>       }
>>         ret = rdt_pseudo_lock_init();
>> @@ -3214,6 +3260,8 @@ static void rdt_kill_sb(struct super_block *sb)
>>       cpus_read_lock();
>>       mutex_lock(&rdtgroup_mutex);
>>   +    resctrl_unassign_events(&rdtgroup_default);
>> +
>>       rdt_disable_ctx();
>>         /*Put everything back to default values. */
>> @@ -3752,6 +3800,14 @@ static int rdtgroup_mkdir_mon(struct kernfs_node
>> *parent_kn,
>>           goto out_unlock;
>>       }
>>   +    /*
>> +     * Assign the monitor counters if it is available. If it fails,
>> +     * report the warnings and continue. It is not nessaccery to
>> +     * fail here.
>> +     */
> 
> Fix copy&paste here and below.

Sure.

> 
>> +    if (resctrl_assign_events(rdtgrp) < 0)
>> +        rdt_last_cmd_puts("Monitor assignment failed\n");
>> +
>>       kernfs_activate(rdtgrp->kn);
>>         /*
>> @@ -3796,6 +3852,14 @@ static int rdtgroup_mkdir_ctrl_mon(struct
>> kernfs_node *parent_kn,
>>       if (ret)
>>           goto out_closid_free;
>>   +    /*
>> +     * Assign the monitor counters if it is available. If it fails,
>> +     * report the warnings and continue. It is not nessaccery to
>> +     * fail here.
>> +     */
>> +    if (resctrl_assign_events(rdtgrp) < 0)
>> +        rdt_last_cmd_puts("Monitor assignment failed\n");
>> +
>>       kernfs_activate(rdtgrp->kn);
>>         ret = rdtgroup_init_alloc(rdtgrp);
>> @@ -3891,6 +3955,9 @@ static int rdtgroup_rmdir_mon(struct rdtgroup
>> *rdtgrp, cpumask_var_t tmpmask)
>>       update_closid_rmid(tmpmask, NULL);
>>         rdtgrp->flags = RDT_DELETED;
>> +
>> +    resctrl_unassign_events(rdtgrp);
>> +
>>       free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
>>         /*
>> @@ -3937,6 +4004,8 @@ static int rdtgroup_rmdir_ctrl(struct rdtgroup
>> *rdtgrp, cpumask_var_t tmpmask)
>>       cpumask_or(tmpmask, tmpmask, &rdtgrp->cpu_mask);
>>       update_closid_rmid(tmpmask, NULL);
>>   +    resctrl_unassign_events(rdtgrp);
>> +
>>       free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
>>       closid_free(rdtgrp->closid);
>>   
> 
> Reinette
> 

-- 
Thanks
Babu Moger

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