linux-kernel - Re: [PATCH v9 03/13] x86/cpufeatures: Add Bandwidth Monitoring Event Configuration feature flag

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Message-ID: <b5c6c0c2-6ec7-a01e-75cb-113324298324@intel.com>
Date:   Thu, 15 Dec 2022 09:11:27 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Babu Moger <babu.moger@....com>, <corbet@....net>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>
CC:     <fenghua.yu@...el.com>, <dave.hansen@...ux.intel.com>,
        <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
        <akpm@...ux-foundation.org>, <quic_neeraju@...cinc.com>,
        <rdunlap@...radead.org>, <damien.lemoal@...nsource.wdc.com>,
        <songmuchun@...edance.com>, <peterz@...radead.org>,
        <jpoimboe@...nel.org>, <pbonzini@...hat.com>,
        <chang.seok.bae@...el.com>, <pawan.kumar.gupta@...ux.intel.com>,
        <jmattson@...gle.com>, <daniel.sneddon@...ux.intel.com>,
        <sandipan.das@....com>, <tony.luck@...el.com>,
        <james.morse@....com>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <bagasdotme@...il.com>,
        <eranian@...gle.com>, <christophe.leroy@...roup.eu>,
        <jarkko@...nel.org>, <adrian.hunter@...el.com>,
        <quic_jiles@...cinc.com>, <peternewman@...gle.com>
Subject: Re: [PATCH v9 03/13] x86/cpufeatures: Add Bandwidth Monitoring Event
 Configuration feature flag

Hi Babu,

On 12/1/2022 7:36 AM, Babu Moger wrote:
> Newer AMD processors support the new feature Bandwidth Monitoring Event
> Configuration (BMEC).
> 
> The feature support is identified via CPUID Fn8000_0020_EBX_x0 (ECX=0).
> Bits    Field Name    Description
> 3       EVT_CFG       Bandwidth Monitoring Event Configuration (BMEC)
> 
> Currently, the bandwidth monitoring events mbm_total_bytes and

Please drop "Currently,".

> mbm_local_bytes are set to count all the total and local reads/writes
> respectively. With the introduction of slow memory, the two counters
> are not enough to count all the different types of memory events. With
> the feature BMEC, the users have the option to configure
> mbm_total_bytes and mbm_local_bytes to count the specific type of
> events.
> 
> Each BMEC event has a configuration MSR, which contains one field for
> each bandwidth type that can be used to configure the bandwidth event
> to track any combination of supported bandwidth types. The event will
> count requests from every bandwidth type bit that is set in the
> corresponding configuration register.
> 
> Following are the types of events supported:
> 
> ====    ========================================================
> Bits    Description
> ====    ========================================================
> 6       Dirty Victims from the QOS domain to all types of memory
> 5       Reads to slow memory in the non-local NUMA domain
> 4       Reads to slow memory in the local NUMA domain
> 3       Non-temporal writes to non-local NUMA domain
> 2       Non-temporal writes to local NUMA domain
> 1       Reads to memory in the non-local NUMA domain
> 0       Reads to memory in the local NUMA domain
> ====    ========================================================
> 
> By default, the mbm_total_bytes configuration is set to 0x7F to count
> all the event types and the mbm_local_bytes configuration is set to
> 0x15 to count all the local memory events.
> 
> Feature description is available in the specification, "AMD64
> Technology Platform Quality of Service Extensions, Revision: 1.03
> Publication

Missing end quote above.

> 
> Link: https://www.amd.com/en/support/tech-docs/amd64-technology-platform-quality-service-extensions
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
> Signed-off-by: Babu Moger <babu.moger@....com>

Same comment about "Link:" ordering as for patch 1.

> ---
>  arch/x86/include/asm/cpufeatures.h |    1 +
>  arch/x86/kernel/cpu/cpuid-deps.c   |    2 ++
>  arch/x86/kernel/cpu/scattered.c    |    1 +
>  3 files changed, 4 insertions(+)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index b6a45e56cd0c..415796d7b309 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -308,6 +308,7 @@
>  #define X86_FEATURE_CALL_DEPTH		(11*32+19) /* "" Call depth tracking for RSB stuffing */
>  #define X86_FEATURE_MSR_TSX_CTRL	(11*32+20) /* "" MSR IA32_TSX_CTRL (Intel) implemented */
>  #define X86_FEATURE_SMBA		(11*32+21) /* Slow Memory Bandwidth Allocation */
> +#define X86_FEATURE_BMEC		(11*32+22) /* Bandwidth Monitoring Event Configuration */
>  
>  /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
>  #define X86_FEATURE_AVX_VNNI		(12*32+ 4) /* AVX VNNI instructions */
> diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
> index d95221117129..f6748c8bd647 100644
> --- a/arch/x86/kernel/cpu/cpuid-deps.c
> +++ b/arch/x86/kernel/cpu/cpuid-deps.c
> @@ -68,6 +68,8 @@ static const struct cpuid_dep cpuid_deps[] = {
>  	{ X86_FEATURE_CQM_OCCUP_LLC,		X86_FEATURE_CQM_LLC   },
>  	{ X86_FEATURE_CQM_MBM_TOTAL,		X86_FEATURE_CQM_LLC   },
>  	{ X86_FEATURE_CQM_MBM_LOCAL,		X86_FEATURE_CQM_LLC   },
> +	{ X86_FEATURE_BMEC,			X86_FEATURE_CQM_MBM_TOTAL   },
> +	{ X86_FEATURE_BMEC,			X86_FEATURE_CQM_MBM_LOCAL   },
>  	{ X86_FEATURE_AVX512_BF16,		X86_FEATURE_AVX512VL  },
>  	{ X86_FEATURE_AVX512_FP16,		X86_FEATURE_AVX512BW  },
>  	{ X86_FEATURE_ENQCMD,			X86_FEATURE_XSAVES    },
> diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
> index d925753084fb..0dad49a09b7a 100644
> --- a/arch/x86/kernel/cpu/scattered.c
> +++ b/arch/x86/kernel/cpu/scattered.c
> @@ -46,6 +46,7 @@ static const struct cpuid_bit cpuid_bits[] = {
>  	{ X86_FEATURE_PROC_FEEDBACK,    CPUID_EDX, 11, 0x80000007, 0 },
>  	{ X86_FEATURE_MBA,		CPUID_EBX,  6, 0x80000008, 0 },
>  	{ X86_FEATURE_SMBA,		CPUID_EBX,  2, 0x80000020, 0 },
> +	{ X86_FEATURE_BMEC,		CPUID_EBX,  3, 0x80000020, 0 },
>  	{ X86_FEATURE_PERFMON_V2,	CPUID_EAX,  0, 0x80000022, 0 },
>  	{ X86_FEATURE_AMD_LBR_V2,	CPUID_EAX,  1, 0x80000022, 0 },
>  	{ 0, 0, 0, 0, 0 }
> 
> 

With changelog comments addressed:

Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette