Message-ID: <2c3e2a70-7a78-4b80-a2fd-eaf609c2afea@amd.com>
Date: Tue, 16 Jul 2024 15:45:19 -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 13/20] x86/resctrl: Add the interface to assign
 hardware counter

Hi Reinette,

On 7/12/24 17:09, Reinette Chatre wrote:
> Hi Babu,
> 
> On 7/3/24 2:48 PM, Babu Moger wrote:
>> The ABMC feature provides an option to the user to assign a hardware
>> counter to an RMID and monitor the bandwidth as long as it is assigned.
>> The assigned RMID will be tracked by the hardware until the user unassigns
>> it manually.
>>
>> Individual counters are configured by writing to L3_QOS_ABMC_CFG MSR
>> and specifying the counter id, bandwidth source, and bandwidth types.
>>
>> Provide the interface to assign the counter ids to RMID.
>>
> 
> Again this is a mix of a couple of layers where this single patch
> introduces fs code (mbm_cntr_alloc() and rdtgroup_assign_cntr()) as well
> as architecture specific code (resctrl_arch_assign_cntr() and
> rdtgroup_abmc_cfg()).
> Lumping this all together without any guidance to reader makes this very
> difficult
> to navigate. This work needs to be split into fs and arch parts with
> clear descriptions of how the layers interact.

Agree. We need to separate it. Will do.

> 
>> The feature details are documented in the APM listed below [1].
>> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
>>      Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable
>> Bandwidth
>>      Monitoring (ABMC).
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
>> ---
>> v5: Few name changes to match cntr_id.
>>      Changed the function names to
>>      rdtgroup_assign_cntr
>>      resctr_arch_assign_cntr
>>      More comments on commit log.
>>      Added function summary.
>>
>> v4: Commit message update.
>>      User bitmap APIs where applicable.
>>      Changed the interfaces considering MPAM(arm).
>>      Added domain specific assignment.
>>
>> v3: Removed the static from the prototype of rdtgroup_assign_abmc.
>>      The function is not called directly from user anymore. These
>>      changes are related to global assignment interface.
>>
>> v2: Minor text changes in commit message.
>> ---
>>   arch/x86/kernel/cpu/resctrl/internal.h |  3 +
>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 96 ++++++++++++++++++++++++++
>>   2 files changed, 99 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h
>> b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 6925c947682d..66460375056c 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -708,6 +708,9 @@ void __init resctrl_file_fflags_init(const char
>> *config,
>>                        unsigned long fflags);
>>   void resctrl_arch_mbm_evt_config(struct rdt_hw_mon_domain *hw_dom);
>>   unsigned int mon_event_config_index_get(u32 evtid);
>> +int resctrl_arch_assign_cntr(struct rdt_mon_domain *d, u32 evtid, u32
>> rmid,
>> +                 u32 cntr_id, u32 closid, bool enable);
>> +int rdtgroup_assign_cntr(struct rdtgroup *rdtgrp, u32 evtid);
>>   void rdt_staged_configs_clear(void);
>>   bool closid_allocated(unsigned int closid);
>>   int resctrl_find_cleanest_closid(void);
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index d2663f1345b7..44f6eff42c30 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -202,6 +202,19 @@ static void mbm_cntrs_init(void)
>>       mbm_cntrs_free_map_len = r->mon.num_mbm_cntrs;
>>   }
>>   +static int mbm_cntr_alloc(void)
>> +{
>> +    u32 cntr_id = find_first_bit(&mbm_cntrs_free_map,
>> +                     mbm_cntrs_free_map_len);
>> +
>> +    if (cntr_id >= mbm_cntrs_free_map_len)
>> +        return -ENOSPC;
>> +
>> +    __clear_bit(cntr_id, &mbm_cntrs_free_map);
>> +
>> +    return cntr_id;
>> +}
>> +
>>   /**
>>    * rdtgroup_mode_by_closid - Return mode of resource group with closid
>>    * @closid: closid if the resource group
>> @@ -1860,6 +1873,89 @@ static ssize_t
>> mbm_local_bytes_config_write(struct kernfs_open_file *of,
>>       return ret ?: nbytes;
>>   }
>>   +static void rdtgroup_abmc_cfg(void *info)
>> +{
>> +    u64 *msrval = info;
>> +
>> +    wrmsrl(MSR_IA32_L3_QOS_ABMC_CFG, *msrval);
>> +}
>> +
>> +/*
>> + * Send an IPI to the domain to assign the counter id to RMID.
>> + */
>> +int resctrl_arch_assign_cntr(struct rdt_mon_domain *d, u32 evtid, u32
>> rmid,
> 
> u32 evtid -> enum resctrl_event_id evtid

Sure.

> 
>> +                 u32 cntr_id, u32 closid, bool enable)
>> +{
>> +    struct rdt_hw_mon_domain *hw_dom = resctrl_to_arch_mon_dom(d);
>> +    union l3_qos_abmc_cfg abmc_cfg = { 0 };
>> +    struct arch_mbm_state *arch_mbm;
>> +
>> +    abmc_cfg.split.cfg_en = 1;
>> +    abmc_cfg.split.cntr_en = enable ? 1 : 0;
>> +    abmc_cfg.split.cntr_id = cntr_id;
>> +    abmc_cfg.split.bw_src = rmid;
>> +
>> +    /* Update the event configuration from the domain */
>> +    if (evtid == QOS_L3_MBM_TOTAL_EVENT_ID) {
>> +        abmc_cfg.split.bw_type = hw_dom->mbm_total_cfg;
>> +        arch_mbm = &hw_dom->arch_mbm_total[rmid];
>> +    } else {
>> +        abmc_cfg.split.bw_type = hw_dom->mbm_local_cfg;
>> +        arch_mbm = &hw_dom->arch_mbm_local[rmid];
>> +    }
>> +
>> +    smp_call_function_any(&d->hdr.cpu_mask, rdtgroup_abmc_cfg,
>> &abmc_cfg, 1);
>> +
>> +    /*
>> +     * Reset the architectural state so that reading of hardware
>> +     * counter is not considered as an overflow in next update.
>> +     */
>> +    if (arch_mbm)
>> +        memset(arch_mbm, 0, sizeof(struct arch_mbm_state));
>> +
>> +    return 0;
>> +}
>> +
>> +/*
>> + * Assign a hardware counter id to the group. Allocate a new counter id
>> + * if the event is unassigned.
>> + */
>> +int rdtgroup_assign_cntr(struct rdtgroup *rdtgrp, u32 evtid)
> 
> u32 evtid -> enum resctrl_event_id evtid

Sure.

> 
>> +{
>> +    struct rdt_resource *r =
>> &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
>> +    int cntr_id = 0, index;
>> +    struct rdt_mon_domain *d;
> 
> reverse fir

Sure.

> 
>> +
>> +    index = mon_event_config_index_get(evtid);
>> +    if (index == INVALID_CONFIG_INDEX) {
>> +        rdt_last_cmd_puts("Invalid event id\n");
> 
> This is a kernel bug and can be a WARN (once) instead. No need to message
> user space.

Sure.

> 
>> +        return -EINVAL;
>> +    }
>> +
>> +    /* Nothing to do if event has been assigned already */
>> +    if (rdtgrp->mon.cntr_id[index] != MON_CNTR_UNSET) {
>> +        rdt_last_cmd_puts("ABMC counter is assigned already\n");
>> +        return 0;
>> +    }
>> +
>> +    /*
>> +     * Allocate a new counter id and update domains
>> +     */
>> +    cntr_id = mbm_cntr_alloc();
>> +    if (cntr_id < 0) {
>> +        rdt_last_cmd_puts("Out of ABMC counters\n");
>> +        return -ENOSPC;
>> +    }
>> +
>> +    rdtgrp->mon.cntr_id[index] = cntr_id;
>> +
>> +    list_for_each_entry(d, &r->mon_domains, hdr.list)
>> +        resctrl_arch_assign_cntr(d, evtid, rdtgrp->mon.rmid,
>> +                     cntr_id, rdtgrp->closid, 1);
>> +
>> +    return 0;
>> +}
>> +
>>   /* rdtgroup information files for one cache resource. */
>>   static struct rftype res_common_files[] = {
>>       {
> 
> Reinette
> 

-- 
Thanks
Babu Moger

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