linux-kernel - Re: [PATCH v5 03/11] perf/x86/intel/pt: Introduce a new function to get the capability of Intel PT

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Date:   Mon, 19 Mar 2018 10:04:36 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Kang, Luwei" <luwei.kang@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Cc:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "joro@...tes.org" <joro@...tes.org>
Subject: Re: [PATCH v5 03/11] perf/x86/intel/pt: Introduce a new function to
 get the capability of Intel PT

On 19/03/2018 08:17, Kang, Luwei wrote:
>>> +u32 pt_cap_get_ex(u32 *caps, enum pt_capabilities cap) {
>>> +	struct pt_cap_desc *cd = &pt_caps[cap];
>>> +	u32 c = caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
>>> +	unsigned int shift = __ffs(cd->mask);
>>> +
>>> +	return (c & cd->mask) >> shift;
>>> +}
>>> +EXPORT_SYMBOL_GPL(pt_cap_get_ex);
>>> +
>>
>> You should change pt_cap_get to use this function.  Also, "_ex" is not a very common suffix, so perhaps you can call it
>> __pt_cap_get.
>>
>> I don't have any other comments on patches 1-3, so when you resend we can ask the x86 maintainers for approval.
>>
> 
> Hi Paolo,
>     Is that like this?

Yes, thanks.

Paolo

> --- a/arch/x86/events/intel/pt.c
> +++ b/arch/x86/events/intel/pt.c
> @@ -76,14 +76,20 @@
>         PT_CAP(psb_periods,             1, CPUID_EBX, 0xffff0000),
>  };
> 
> -u32 pt_cap_get(enum pt_capabilities cap)
> +u32 __pt_cap_get(u32 *caps, enum pt_capabilities cap)
>  {
>         struct pt_cap_desc *cd = &pt_caps[cap];
> -       u32 c = pt_pmu.caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
> +       u32 c = caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
>         unsigned int shift = __ffs(cd->mask);
> 
>         return (c & cd->mask) >> shift;
>  }
> +EXPORT_SYMBOL_GPL(__pt_cap_get);
> +
> +u32 pt_cap_get(enum pt_capabilities cap)
> +{
> +       return __pt_cap_get(pt_pmu.caps, cap);
> +}
>  EXPORT_SYMBOL_GPL(pt_cap_get);
> 
>  static ssize_t pt_cap_show(struct device *cdev,
> diff --git a/arch/x86/include/asm/intel_pt.h b/arch/x86/include/asm/intel_pt.h
> index 2de4db0..3a4f524 100644
> --- a/arch/x86/include/asm/intel_pt.h
> +++ b/arch/x86/include/asm/intel_pt.h
> @@ -27,9 +27,11 @@ enum pt_capabilities {
>  #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)
>  void cpu_emergency_stop_pt(void);
>  extern u32 pt_cap_get(enum pt_capabilities cap);
> +extern u32 __pt_cap_get(u32 *caps, enum pt_capabilities cap);
>  #else
>  static inline void cpu_emergency_stop_pt(void) {}
>  static inline u32 pt_cap_get(enum pt_capabilities cap) { return 0; }
> +static u32 __pt_cap_get(u32 *caps, enum pt_capabilities cap) { return 0; }
> 
> 
> Thanks,
> Luwei Kang
>