linux-kernel - Re: [PATCH v6 13/22] x86/resctrl: Add data structures and definitions for ABMC assignment

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Message-ID: <498fead6-8b03-4a68-8fb5-15c239e9b63e@intel.com>
Date: Fri, 16 Aug 2024 14:38:31 -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 v6 13/22] x86/resctrl: Add data structures and definitions
 for ABMC assignment

Hi Babu,

This patch now only introduces one data structure so the subject could
be made more specific.

On 8/6/24 3:00 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 the counter
> is assigned. The bandwidth events will be tracked by the hardware until
> the user changes the configuration. Each resctrl group can configure
> maximum two counters, one for total event and one for local event.
> 
> 

(extra empty line)

> The ABMC feature implements a pair of MSRs, L3_QOS_ABMC_CFG (C000_03FDh)
> and L3_QOS_ABMC_DSC (C000_3FEh). The counters are configured by writing
> to MSR L3_QOS_ABMC_CFG. Configuration is done by setting the counter id,
> bandwidth source (RMID) and bandwidth configuration supported by BMEC
> (Bandwidth Monitoring Event Configuration).
> 
> L3_QOS_ABMC_DSC is a read-only MSR. Reading L3_QOS_ABMC_DSC returns the
> configuration of the counter id specified in L3_QOS_ABMC_CFG.cntr_id
> with rmid(bw_src) and event configuration(bw_type).
> 
> Attempts to read or write these MSRs when ABMC is not enabled will result
> in a #GP(0) exception.
> 
> Introduce data structures and definitions for ABMC MSRs.
> 
> MSR L3_QOS_ABMC_CFG (0xC000_03FDh) and L3_QOS_ABMC_DSC (0xC000_03FEh)
> details.

The changelog and patch introduce L3_QOS_ABMC_DSC but I cannot see that it is
used in this series.

> =========================================================================
> Bits 	Mnemonic	Description			Access Reset
> 							Type   Value
> =========================================================================
> 63 	CfgEn 		Configuration Enable 		R/W 	0
> 
> 62 	CtrEn 		Enable/disable Tracking		R/W 	0
> 
> 61:53 	– 		Reserved 			MBZ 	0
> 
> 52:48 	CtrID 		Counter Identifier		R/W	0
> 
> 47 	IsCOS		BwSrc field is a CLOSID		R/W	0
> 			(not an RMID)
> 
> 46:44 	–		Reserved			MBZ	0
> 
> 43:32	BwSrc		Bandwidth Source		R/W	0
> 			(RMID or CLOSID)
> 
> 31:0	BwType		Bandwidth configuration		R/W	0
> 			to track for this counter
> ==========================================================================
> 
> Configuration and tracking:
> CfgEn=1,CtrEn=0 : Configure CtrID and but no tracking the events yet.
> CfgEn=1,CtrEn=1 : Configure CtrID and start tracking events.

Could you please add the above snippet noting field combinations to the
kernel-doc of the union?

> 
> 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>
> ---
> v6: Removed all the fs related changes.
>      Added note on CfgEn,CtrEn.
>      Removed the definitions which are not used.
>      Removed cntr_id initialization.
> 
> v5: Moved assignment flags here (path 10/19 of v4).
>      Added MON_CNTR_UNSET definition to initialize cntr_id's.
>      More details in commit log.
>      Renamed few fields in l3_qos_abmc_cfg for readability.
> 
> v4: Added more descriptions.
>      Changed the name abmc_ctr_id to ctr_id.
>      Added L3_QOS_ABMC_DSC. Used for reading the configuration.
> 
> v3: No changes.
> 
> v2: No changes.
> ---
>   arch/x86/include/asm/msr-index.h       |  2 ++
>   arch/x86/kernel/cpu/resctrl/internal.h | 26 ++++++++++++++++++++++++++
>   2 files changed, 28 insertions(+)
> 
> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
> index d86469bf5d41..5b3931a59d5a 100644
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -1183,6 +1183,8 @@
>   #define MSR_IA32_SMBA_BW_BASE		0xc0000280
>   #define MSR_IA32_EVT_CFG_BASE		0xc0000400
>   #define MSR_IA32_L3_QOS_EXT_CFG		0xc00003ff
> +#define MSR_IA32_L3_QOS_ABMC_CFG	0xc00003fd
> +#define MSR_IA32_L3_QOS_ABMC_DSC	0xc00003fe
>   
>   /* MSR_IA32_VMX_MISC bits */
>   #define MSR_IA32_VMX_MISC_INTEL_PT                 (1ULL << 14)
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 1021227d8c7e..af3efa35a62e 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -589,6 +589,32 @@ union cpuid_0x10_x_edx {
>   	unsigned int full;
>   };
>   
> +/*
> + * ABMC counters can be configured by writing to L3_QOS_ABMC_CFG.
> + * @bw_type		: Bandwidth configuration(supported by BMEC)
> + *			  tracked by the @cntr_id.
> + * @bw_src		: Bandwidth source (RMID or CLOSID).
> + * @reserved1		: Reserved.
> + * @is_clos		: @bw_src field is a CLOSID (not an RMID).
> + * @cntr_id		: Counter identifier.
> + * @reserved		: Reserved.
> + * @cntr_en		: Tracking enable bit.
> + * @cfg_en		: Configuration enable bit.
> + */
> +union l3_qos_abmc_cfg {
> +	struct {
> +		unsigned long	bw_type	:32,
> +				bw_src	:12,
> +				reserved1: 3,
> +				is_clos	: 1,
> +				cntr_id	: 5,
> +				reserved : 9,
> +				cntr_en	: 1,
> +				cfg_en	: 1;
> +	} split;
> +	unsigned long full;
> +};
> +

This data structure still uses tabs that seem to have goal of aligning members
but the tabs are used inconsistently and members are not lining up either.

>   void rdt_last_cmd_clear(void);
>   void rdt_last_cmd_puts(const char *s);
>   __printf(1, 2)

Reinette