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 07:17:07 +0000
From:   "Kang, Luwei" <luwei.kang@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.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

> > +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?

--- 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