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Wed, 29 Apr 2020 03:21:26 -0700 (PDT) Received: from [192.168.10.150] ([93.56.170.5]) by smtp.gmail.com with ESMTPSA id 36sm30729577wrc.35.2020.04.29.03.21.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Apr 2020 03:21:26 -0700 (PDT) Subject: Re: [PATCH][v2] kvm: x86: emulate APERF/MPERF registers To: Peter Zijlstra , Li RongQing Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, hpa@zytor.com, bp@alien8.de, mingo@redhat.com, tglx@linutronix.de, joro@8bytes.org, jmattson@google.com, wanpengli@tencent.com, vkuznets@redhat.com, sean.j.christopherson@intel.com References: <1588139196-23802-1-git-send-email-lirongqing@baidu.com> <20200429085440.GG13592@hirez.programming.kicks-ass.net> From: Paolo Bonzini Message-ID: <201824a4-6b0f-9061-ec21-26d71fa11bc4@redhat.com> Date: Wed, 29 Apr 2020 12:21:25 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200429085440.GG13592@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 29/04/20 10:54, Peter Zijlstra wrote: > On Wed, Apr 29, 2020 at 01:46:36PM +0800, Li RongQing wrote: >> Guest kernel reports a fixed cpu frequency in /proc/cpuinfo, >> this is confused to user when turbo is enable, and aperf/mperf >> can be used to show current cpu frequency after 7d5905dc14a >> "(x86 / CPU: Always show current CPU frequency in /proc/cpuinfo)" >> so we should emulate aperf mperf to achieve it >> >> the period of aperf/mperf in guest mode are accumulated as >> emulated value, and add per-VM knod to enable emulate mperfaperf >> >> diff v1: >> 1. support AMD >> 2. support per-vm capability to enable > Would it make sense to provide a pass-through APERF/MPERF for > KVM_HINTS_REALTIME ? Because that hint guarantees we have a 1:1 vCPU:CPU > binding and guaranteed no over-commit. > Yes but that's up to userspace. Paolo