linux-kernel - RE: [patch v2 4/8] KVM: x86: add Intel processor trace cpuid emulataion

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Date:   Tue, 14 Nov 2017 02:56:59 +0000
From:   "Kang, Luwei" <luwei.kang@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
CC:     "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Chao Peng <chao.p.peng@...ux.intel.com>
Subject: RE: [patch v2 4/8] KVM: x86: add Intel processor trace cpuid
 emulataion

> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index
> > 0099e10..ef19a11 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -70,6 +70,7 @@ u64 kvm_supported_xcr0(void)
> >  /* These are scattered features in cpufeatures.h. */
> >  #define KVM_CPUID_BIT_AVX512_4VNNIW     2
> >  #define KVM_CPUID_BIT_AVX512_4FMAPS     3
> > +#define KVM_CPUID_BIT_INTEL_PT		25
> 
> This is not necessary, because there is no need to place processor tracing in scattered features.  Can you replace this hunk, and the KF usage below, with the following patch?
> 

Yes, this looks good to me. will fix in next version. 

Thanks,
Luwei Kang

> ------------ 8< -------------
> From: Paolo Bonzini <pbonzini@...hat.com>
> Subject: [PATCH] x86: cpufeature: move processor tracing out of scattered features
> 
> Processor tracing is already enumerated in word 9 (CPUID[7,0].EBX), so do not duplicate it in the scattered features word.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  arch/x86/include/asm/cpufeatures.h | 3 ++-
>  arch/x86/kernel/cpu/scattered.c    | 1 -
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 2519c6c801c9..839781e78763 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -199,7 +199,7 @@
>  #define X86_FEATURE_SME		( 7*32+10) /* AMD Secure Memory Encryption */
> 
>  #define X86_FEATURE_INTEL_PPIN	( 7*32+14) /* Intel Processor Inventory Number */
> -#define X86_FEATURE_INTEL_PT	( 7*32+15) /* Intel Processor Trace */
> +
>  #define X86_FEATURE_AVX512_4VNNIW (7*32+16) /* AVX-512 Neural Network Instructions */  #define
> X86_FEATURE_AVX512_4FMAPS (7*32+17) /* AVX-512 Multiply Accumulation Single precision */
> 
> @@ -238,6 +238,7 @@
>  #define X86_FEATURE_AVX512IFMA  ( 9*32+21) /* AVX-512 Integer Fused Multiply-Add instructions */
>  #define X86_FEATURE_CLFLUSHOPT	( 9*32+23) /* CLFLUSHOPT instruction */
>  #define X86_FEATURE_CLWB	( 9*32+24) /* CLWB instruction */
> +#define X86_FEATURE_INTEL_PT	( 9*32+25) /* Intel Processor Trace */
>  #define X86_FEATURE_AVX512PF	( 9*32+26) /* AVX-512 Prefetch */
>  #define X86_FEATURE_AVX512ER	( 9*32+27) /* AVX-512 Exponential and Reciprocal */
>  #define X86_FEATURE_AVX512CD	( 9*32+28) /* AVX-512 Conflict Detection */
> diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c index 05459ad3db46..d0e69769abfd 100644
> --- a/arch/x86/kernel/cpu/scattered.c
> +++ b/arch/x86/kernel/cpu/scattered.c
> @@ -21,7 +21,6 @@ struct cpuid_bit {
>  static const struct cpuid_bit cpuid_bits[] = {
>  	{ X86_FEATURE_APERFMPERF,       CPUID_ECX,  0, 0x00000006, 0 },
>  	{ X86_FEATURE_EPB,		CPUID_ECX,  3, 0x00000006, 0 },
> -	{ X86_FEATURE_INTEL_PT,		CPUID_EBX, 25, 0x00000007, 0 },
>  	{ X86_FEATURE_AVX512_4VNNIW,    CPUID_EDX,  2, 0x00000007, 0 },
>  	{ X86_FEATURE_AVX512_4FMAPS,    CPUID_EDX,  3, 0x00000007, 0 },
>  	{ X86_FEATURE_CAT_L3,		CPUID_EBX,  1, 0x00000010, 0 },
> 
> >  #define KF(x) bit(KVM_CPUID_BIT_##x)
> >
> >  int kvm_update_cpuid(struct kvm_vcpu *vcpu) @@ -327,6 +328,7 @@
> > static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
> >  	unsigned f_invpcid = kvm_x86_ops->invpcid_supported() ? F(INVPCID) : 0;
> >  	unsigned f_mpx = kvm_mpx_supported() ? F(MPX) : 0;
> >  	unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0;
> > +	unsigned f_intel_pt = kvm_x86_ops->pt_supported() ? KF(INTEL_PT) :
> > +0;
> >
> >  	/* cpuid 1.edx */
> >  	const u32 kvm_cpuid_1_edx_x86_features =