linux-kernel - RE: [PATCH v8 01/13] x86/cpufeatures: Add Slow Memory Bandwidth Allocation feature flag

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Message-ID: <MW3PR12MB45530573696D249A74B674B1950C9@MW3PR12MB4553.namprd12.prod.outlook.com>
Date:   Wed, 23 Nov 2022 23:09:51 +0000
From:   "Moger, Babu" <Babu.Moger@....com>
To:     "Yu, Fenghua" <fenghua.yu@...el.com>,
        "corbet@....net" <corbet@....net>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>
CC:     "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "paulmck@...nel.org" <paulmck@...nel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "quic_neeraju@...cinc.com" <quic_neeraju@...cinc.com>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "damien.lemoal@...nsource.wdc.com" <damien.lemoal@...nsource.wdc.com>,
        "songmuchun@...edance.com" <songmuchun@...edance.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "jpoimboe@...nel.org" <jpoimboe@...nel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Bae, Chang Seok" <chang.seok.bae@...el.com>,
        "pawan.kumar.gupta@...ux.intel.com" 
        <pawan.kumar.gupta@...ux.intel.com>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "daniel.sneddon@...ux.intel.com" <daniel.sneddon@...ux.intel.com>,
        "Das1, Sandipan" <Sandipan.Das@....com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "james.morse@....com" <james.morse@....com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "Eranian, Stephane" <eranian@...gle.com>
Subject: RE: [PATCH v8 01/13] x86/cpufeatures: Add Slow Memory Bandwidth
 Allocation feature flag

[AMD Official Use Only - General]

Hi Fenghua,

> -----Original Message-----
> From: Yu, Fenghua <fenghua.yu@...el.com>
> Sent: Wednesday, November 23, 2022 12:22 PM
> To: Moger, Babu <Babu.Moger@....com>; corbet@....net; Chatre, Reinette
> <reinette.chatre@...el.com>; tglx@...utronix.de; mingo@...hat.com;
> bp@...en8.de
> Cc: 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; Bae, Chang Seok <chang.seok.bae@...el.com>;
> pawan.kumar.gupta@...ux.intel.com; jmattson@...gle.com;
> daniel.sneddon@...ux.intel.com; Das1, Sandipan <Sandipan.Das@....com>;
> Luck, Tony <tony.luck@...el.com>; james.morse@....com; linux-
> doc@...r.kernel.org; linux-kernel@...r.kernel.org; bagasdotme@...il.com;
> Eranian, Stephane <eranian@...gle.com>
> Subject: RE: [PATCH v8 01/13] x86/cpufeatures: Add Slow Memory Bandwidth
> Allocation feature flag
> 
> Hi, Babu,
> 
> > diff --git a/arch/x86/include/asm/cpufeatures.h
> > b/arch/x86/include/asm/cpufeatures.h
> > index aefd0816a333..d68b4c9c181d 100644
> > --- a/arch/x86/include/asm/cpufeatures.h
> > +++ b/arch/x86/include/asm/cpufeatures.h
> > @@ -305,6 +305,7 @@
> >  #define X86_FEATURE_USE_IBPB_FW		(11*32+16) /* "" Use IBPB
> > during runtime firmware calls */
> >  #define X86_FEATURE_RSB_VMEXIT_LITE	(11*32+17) /* "" Fill RSB on
> VM
> > exit when EIBRS is enabled */
> >  #define X86_FEATURE_CALL_DEPTH		(11*32+18) /* "" Call depth
> > tracking for RSB stuffing */
> > +#define X86_FEATURE_SMBA		(11*32+19) /* Slow Memory
> > Bandwidth Allocation */
> >
> >  /* 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/scattered.c
> > b/arch/x86/kernel/cpu/scattered.c index fc01f81f6e2a..5a5f17ed69a2
> > 100644
> > --- a/arch/x86/kernel/cpu/scattered.c
> > +++ b/arch/x86/kernel/cpu/scattered.c
> > @@ -44,6 +44,7 @@ static const struct cpuid_bit cpuid_bits[] = {
> >  	{ X86_FEATURE_CPB,		CPUID_EDX,  9, 0x80000007, 0 },
> >  	{ 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_PERFMON_V2,	CPUID_EAX,  0, 0x80000022, 0 },
> >  	{ X86_FEATURE_AMD_LBR_V2,	CPUID_EAX,  1, 0x80000022, 0 },
> >  	{ 0, 0, 0, 0, 0 }
> >
> 
> Shouldn't X86_FEATURE_SMBA depend on X86_FEATURE_MBA? Need to add
> the dependency in cpuid-deps.c

I won't consider them as dependents. They both have separate CPUID bits and MSRs.
Thanks
Babu

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