linux-kernel - 答复: [PATCH] [RFC] kvm: x86: emulate APERF/MPERF registers

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Message-ID: <4fecc02b00f6469e81ffc40de4f7188c@baidu.com>
Date:   Sun, 26 Apr 2020 08:30:26 +0000
From:   "Li,Rongqing" <lirongqing@...du.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "joro@...tes.org" <joro@...tes.org>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>
Subject: 答复: [PATCH] [RFC] kvm: x86: emulate APERF/MPERF registers

> 
> But then here you only emulate it for VMX, which then results in SVM guests
> going wobbly.
> 
> Also, on Intel, the moment you advertise APERFMPERF, we'll try and read
> MSR_PLATFORM_INFO / MSR_TURBO_RATIO_LIMIT*, I don't suppose you're
> passing those through as well?
> 

init_freq_invariance(void) is trying read MSR_PLATFORM_INFO / MSR_TURBO_RATIO_LIMIT*,
should we add a check of turbo status in init_freq_invariance, to avoid the reading?

It is unnecessary to call intel_set_max_freq_ratio  If turbo is disabled

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index fe3ab9632f3b..54fb88323293 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -2009,6 +2009,9 @@ static void init_freq_invariance(void)
        if (smp_processor_id() != 0 || !boot_cpu_has(X86_FEATURE_APERFMPERF))
                return;
 
+       if (turbo_disabled())
+               return;
+
        if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
                ret = intel_set_max_freq_ratio();

-Li