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Date: Wed, 19 Jun 2024 17:38:19 -0500
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>,
Babu Moger <babu.moger@....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 14/19] x86/resctrl: Add the interface to assign ABMC
counter
Hi Reinette,
On 6/13/2024 8:48 PM, Reinette Chatre wrote:
> Hi Babu,
>
> On 5/24/24 5:23 AM, Babu Moger wrote:
>> ABMC feature requires to users to assign a hardware counter to an RMID
>
> "requires to users" -> "requires users"?
Sure.
>
>> to monitor the events. Provide the interfaces to assign a counter.
>>
>> Individual counters are configured by writing to L3_QOS_ABMC_CFG MSR
>> and specifying the counter id, bandwidth source, and bandwidth types.
>
> Where is discription of what this patch does and why?
>
> This and following patches seem to introduce building blocks that
> are only used later in series. These building blocks are introduced
> without any information about what they do and why and that makes it
> difficult to understand how this work will fall into place.
Ok. Will elaborate this.
>
>>
>> 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
>> ---
>> 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 | 101 +++++++++++++++++++++++++
>> 2 files changed, 104 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h
>> b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 45ed33f4f0ff..a88c8fc5e4df 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -657,6 +657,9 @@ void rdt_domain_reconfigure_cdp(struct
>> rdt_resource *r);
>> void __init resctrl_file_fflags_init(const char *config,
>> unsigned long fflags);
>> void arch_domain_mbm_evt_config(struct rdt_hw_domain *hw_dom);
>> +int resctrl_arch_assign(struct rdt_domain *d, u32 evtid, u32 rmid,
>> + u32 ctr_id, u32 closid, bool enable);
>> +int resctrl_grp_assign(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 0e425c91fa46..48df76499a04 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -203,6 +203,19 @@ static void num_cntrs_init(void)
>> num_cntrs_free_map_len = r->mon.num_cntrs;
>> }
>> +static int assign_cntrs_alloc(void)
>
> Only one counter is allocated and "assign" is unexpected since it
> seems to imply how this counter will be used.
> It can just be "mon_cntr_alloc()"?
Sure.
>
>> +{
>> + u32 ctr_id = find_first_bit(&num_cntrs_free_map,
>> + num_cntrs_free_map_len);
>> +
>> + if (ctr_id >= num_cntrs_free_map_len)
>> + return -ENOSPC;
>> +
>> + __clear_bit(ctr_id, &num_cntrs_free_map);
>> +
>> + return ctr_id;
>> +}
>> +
>> /**
>> * rdtgroup_mode_by_closid - Return mode of resource group with closid
>> * @closid: closid if the resource group
>> @@ -1830,6 +1843,94 @@ 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);
>> +}
>> +
>
> Please add comments to these functions to summarize what
> they do.
Sure.
>
>> +int resctrl_arch_assign(struct rdt_domain *d, u32 evtid, u32 rmid,
>> + u32 ctr_id, u32 closid, bool enable)
>> +{
>> + struct rdt_hw_domain *hw_dom = resctrl_to_arch_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.ctr_en = enable ? 1 : 0;
>> + abmc_cfg.split.ctr_id = ctr_id;
>> + abmc_cfg.split.bw_src = rmid;
>> +
>> + /*
>> + * Read the event configuration from the domain and pass it as
>> + * bw_type.
>> + */
>> + 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->cpu_mask, rdtgroup_abmc_cfg, &abmc_cfg,
>> 1);
>> +
>> + /* Reset the internal counters */
>
> "internal counters"? This needs a definition ... but since this is not
> a new data structure the comment can be more specific about what is done
> and why.
How about?
/* Reset internal mbm event counters. */
>
>> + if (arch_mbm)
>> + memset(arch_mbm, 0, sizeof(struct arch_mbm_state));
>> +
>> + return 0;
>
> If this function always succeeds then it can just be void?
Sure. We can do that.
>
>> +}
>> +
>> +int resctrl_grp_assign(struct rdtgroup *rdtgrp, u32 evtid)
>
> Please use consistent naming. Note how the filename is "rdtgroup.c" and
> this
> function operates on "struct rdtgroup" and if you take a closer look at
> the functions in this file and the header where you add this function you
> will notice a distinct pattern of "rdtgroup_" used as prefix. There really
> is no reason to start a new namespace for this.
Sure.
>
>> +{
>> + struct rdt_resource *r =
>> &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
>> + int ctr_id = 0, index;
>> + struct rdt_domain *d;
>> + u32 mon_state;
>> +
>> + index = mon_event_config_index_get(evtid);
>> + if (index == INVALID_CONFIG_INDEX) {
>> + rdt_last_cmd_puts("Invalid event id\n");
>> + return -EINVAL;
>> + }
>> +
>> + if (evtid == QOS_L3_MBM_TOTAL_EVENT_ID) {
>> + mon_state = ASSIGN_TOTAL;
>> + } else if (evtid == QOS_L3_MBM_LOCAL_EVENT_ID) {
>> + mon_state = ASSIGN_LOCAL;
>> + } else {
>> + rdt_last_cmd_puts("Invalid event id\n");
>> + return -EINVAL;
>> + }
>> +
>> + /* Nothing to do if event has been assigned already */
>> + if (rdtgrp->mon.mon_state & mon_state) {
>
> Why is this mon_state needed? Is it not redundant when considering that
> struct mongroup has an array of counter IDs that can already be used
> to see if a counter is assigned or not?
> What if there is a new:
> #define MON_CNTR_UNSET U32_MAX
>
> When cntr_id[index] == MON_CNTR_UNSET then it is not assigned.
Yes. That can be done. That case mon_state is not required. We just need
the index. Also, we need to initialize the ctrl_id when the group is
created. Hope that should work.
>
>> + rdt_last_cmd_puts("ABMC counter is assigned already\n");
>> + return 0;
>> + }
>> +
>> + /*
>> + * Allocate a new counter and update domains
>> + */
>> + ctr_id = assign_cntrs_alloc();
>> + if (ctr_id < 0) {
>> + rdt_last_cmd_puts("Out of ABMC counters\n");
>> + return -ENOSPC;
>> + }
>> +
>> + rdtgrp->mon.ctr_id[index] = ctr_id;
>> +
>> + list_for_each_entry(d, &r->domains, list)
>> + resctrl_arch_assign(d, evtid, rdtgrp->mon.rmid, ctr_id,
>> + rdtgrp->closid, 1);
>> +
>> + rdtgrp->mon.mon_state |= mon_state;
>> +
>> + return 0;
>> +}
>> +
>> /* rdtgroup information files for one cache resource. */
>> static struct rftype res_common_files[] = {
>> {
>
> Reinette
>
--
- Babu Moger
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