linux-kernel - Re: [PATCH v5 04/20] x86/resctrl: Detect Assignable Bandwidth Monitoring feature details

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Message-ID: <1d0af059-4768-48ce-87ba-7a9a213a3fca@intel.com>
Date: Fri, 12 Jul 2024 15:04:18 -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: [PATCH v5 04/20] x86/resctrl: Detect Assignable Bandwidth
 Monitoring feature details

Hi Babu,

On 7/3/24 2:48 PM, Babu Moger wrote:
> ABMC feature details are reported via CPUID Fn8000_0020_EBX_x5.
> Bits Description
> 15:0 MAX_ABMC Maximum Supported Assignable Bandwidth
>       Monitoring Counter ID + 1
> 
> The feature details are documented in 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).

<insert snippet about what the patch does>

> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
> v5: Name change num_cntrs to num_mbm_cntrs.
>      Moved abmc_capable to resctrl_mon.
> 
> v4: Removed resctrl_arch_has_abmc(). Added all the code inline. We dont
>      need to separate this as arch code.
> 
> v3: Removed changes related to mon_features.
>      Moved rdt_cpu_has to core.c and added new function resctrl_arch_has_abmc.
>      Also moved the fields mbm_assign_capable and mbm_assign_cntrs to
>      rdt_resource. (James)
> 
> v2: Changed the field name to mbm_assign_capable from abmc_capable.
> ---
>   arch/x86/kernel/cpu/resctrl/monitor.c | 12 ++++++++++++
>   include/linux/resctrl.h               |  4 ++++
>   2 files changed, 16 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 795fe91a8feb..87d40f149ebc 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -1229,6 +1229,18 @@ int __init rdt_get_mon_l3_config(struct rdt_resource *r)
>   			mbm_local_event.configurable = true;
>   			mbm_config_rftype_init("mbm_local_bytes_config");
>   		}
> +
> +		if (rdt_cpu_has(X86_FEATURE_ABMC)) {
> +			r->mon.abmc_capable = true;
> +			/*
> +			 * Query CPUID_Fn80000020_EBX_x05 for number of
> +			 * ABMC counters
> +			 */
> +			cpuid_count(0x80000020, 5, &eax, &ebx, &ecx, &edx);
> +			r->mon.num_mbm_cntrs = (ebx & 0xFFFF) + 1;
> +			if (WARN_ON(r->mon.num_mbm_cntrs > 64))
> +				r->mon.num_mbm_cntrs = 64;
> +		}
>   	}
>   
>   	l3_mon_evt_init(r);
> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index e43fc5bb5a3a..62f0f002ef41 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -185,10 +185,14 @@ enum resctrl_scope {
>   /**
>    * struct resctrl_mon - Monitoring related data
>    * @num_rmid:		Number of RMIDs available
> + * @num_mbm_cntrs:	Number of monitoring counters
> + * @abmc_capable:	Is system capable of supporting monitor assignment?
>    * @evt_list:		List of monitoring events
>    */
>   struct resctrl_mon {
>   	int			num_rmid;
> +	int			num_mbm_cntrs;
> +	bool			abmc_capable;
>   	struct list_head	evt_list;
>   };
>   

How about renaming "abmc_capable" to "mbm_cntr_capable? That would,
(a) connect the capability to the "num_mbm_cntrs" property, and (b)
remove the AMD marketing name from the resctrl filesystem code that
will be shared by all architectures.

Reinette