linux-kernel - Re: [RFC PATCH v3 11/17] x86/resctrl: Introduce mbm_total_cfg and mbm_local

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Message-ID: <5c612f5c-7709-49db-b998-a676b61245e1@intel.com>
Date: Fri, 3 May 2024 16:33:02 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: 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: [RFC PATCH v3 11/17] x86/resctrl: Introduce mbm_total_cfg and
 mbm_local_cfg

Hi Babu,

On 3/28/2024 6:06 PM, Babu Moger wrote:
> If the BMEC (Bandwidth Monitoring Event Configuration) feature is
> supported, the bandwidth events can be configured to track specific events.
> The event configuration is domain specific. ABMC (Assignable Bandwidth
> Monitoring Counters) feature needs event configuration information to
> assign RMID to the hardware counter. Currently, this information is not
> available.

hmmm ... "Currently, this information is not available." does not sound
accurate. Perhaps it can be made more specific with something like:
"Event configurations are not stored in resctrl but instead always
read from or written to hardware directly when prompted by user space."
(feel free to improve)

> 
> Save the event configuration information in the rdt_hw_domain, so it can
> be used while for RMID assignment.

"be used while for RMID assignment" -> "be used for RMID assignment"?

> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> 
> ---
> v3: Minor changes related to rebase in mbm_config_write_domain.
> 
> v2: No changes.
> ---
>  arch/x86/kernel/cpu/resctrl/core.c     |  2 ++
>  arch/x86/kernel/cpu/resctrl/internal.h |  3 +++
>  arch/x86/kernel/cpu/resctrl/monitor.c  | 11 +++++++++++
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 16 +++++++++++++++-
>  4 files changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 50e9ec5e547b..ed4f6d49d737 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -555,6 +555,8 @@ static void domain_add_cpu(int cpu, struct rdt_resource *r)
>  		return;
>  	}
>  
> +	arch_domain_mbm_evt_config(hw_dom);
> +
>  	list_add_tail_rcu(&d->list, add_pos);
>  
>  	err = resctrl_online_domain(r, d);
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 41b06d46ea74..88453c86474b 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -385,6 +385,8 @@ struct rdt_hw_domain {
>  	u32				*ctrl_val;
>  	struct arch_mbm_state		*arch_mbm_total;
>  	struct arch_mbm_state		*arch_mbm_local;
> +	u32				mbm_total_cfg;
> +	u32                             mbm_local_cfg;

(please fix tabs/spaces)

>  };
>  
>  static inline struct rdt_hw_domain *resctrl_to_arch_dom(struct rdt_domain *r)
> @@ -648,6 +650,7 @@ void __check_limbo(struct rdt_domain *d, bool force_free);
>  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);
>  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/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 56dc49021540..8677dbf6de43 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -1090,3 +1090,14 @@ void __init intel_rdt_mbm_apply_quirk(void)
>  	mbm_cf_rmidthreshold = mbm_cf_table[cf_index].rmidthreshold;
>  	mbm_cf = mbm_cf_table[cf_index].cf;
>  }
> +
> +void arch_domain_mbm_evt_config(struct rdt_hw_domain *hw_dom)
> +{
> +	if (mbm_total_event.configurable)
> +		hw_dom->mbm_total_cfg = MAX_EVT_CONFIG_BITS;
> +
> +	if (mbm_local_event.configurable)
> +		hw_dom->mbm_local_cfg = READS_TO_LOCAL_MEM |
> +					NON_TEMP_WRITE_TO_LOCAL_MEM |
> +					READS_TO_LOCAL_S_MEM;
> +}

Shouldn't the defaults be discovered from hardware?

Reinette