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

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Date:   Mon, 13 Nov 2017 16:36:19 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Luwei Kang <luwei.kang@...el.com>, kvm@...r.kernel.org
Cc:     rkrcmar@...hat.com, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, x86@...nel.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

On 30/10/2017 23:05, Luwei Kang wrote:
> 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?

Thanks,

Paolo

------------ 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 =