linux-kernel - Re: [PATCH v8 16/25] x86/resctrl: Implement resctrl_arch_config

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Message-ID: <73308f34-cdfb-cf6b-a53a-2f22847757a6@amd.com>
Date: Thu, 17 Oct 2024 17:44:44 -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 v8 16/25] x86/resctrl: Implement
 resctrl_arch_config_cntr() to assign a counter with ABMC

Hi Reinette,

On 10/15/2024 10:23 PM, Reinette Chatre wrote:
> Hi Babu,
> 
> On 10/9/24 10:39 AM, Babu Moger wrote:
>> The ABMC feature provides an option to the user to assign a hardware
>> counter to an RMID, event pair 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.
>>
>> 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.
>>
>> 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).
>>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
> 
> ...
> 
>> ---
>>   arch/x86/kernel/cpu/resctrl/internal.h |  3 ++
>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 45 ++++++++++++++++++++++++++
>>   2 files changed, 48 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 58298db9034f..6d4df0490186 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -705,6 +705,9 @@ int mbm_cntr_alloc(struct rdt_resource *r);
>>   void mbm_cntr_free(struct rdt_resource *r, u32 cntr_id);
>>   void arch_mbm_evt_config_init(struct rdt_hw_mon_domain *hw_dom);
>>   unsigned int mon_event_config_index_get(u32 evtid);
>> +int resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
>> +			     enum resctrl_event_id evtid, u32 rmid, u32 closid,
>> +			     u32 cntr_id, bool assign);
>>   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 03b670b95c49..4ab1a18010c9 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -1853,6 +1853,51 @@ static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
>>   	return ret ?: nbytes;
>>   }
>>   
>> +static void resctrl_abmc_config_one_amd(void *info)
>> +{
>> +	u64 *msrval = info;
>> +
>> +	wrmsrl(MSR_IA32_L3_QOS_ABMC_CFG, *msrval);
>> +}
>> +
>> +/*
>> + * Send an IPI to the domain to assign the counter to RMID, event pair.
>> + */
>> +int resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
>> +			     enum resctrl_event_id evtid, u32 rmid, u32 closid,
>> +			     u32 cntr_id, bool assign)
>> +{
>> +	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 = assign ? 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, resctrl_abmc_config_one_amd,
>> +			      &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));
>> +
> 
> More on this later, but I do believe later code can be simplified if
> reset of architectural state is done by caller. This function should
> focus on just configuring the counter.

Yes. It can be done by the caller. Need to introduce arch handler to do 
this as it accesses the arch state.

> 
>> +	return 0;
>> +}
>> +
>>   /* rdtgroup information files for one cache resource. */
>>   static struct rftype res_common_files[] = {
>>   	{
> 
> Reinette
> 

-- 
- Babu Moger