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AJvYcCWzLOQIidUW2Zbrkj6JfNT2S1fB7n9ItSINlhFdsC9p9F7oEDXAsOMNlJscXMSMJwhSWLmbqhXbtuFMs9g/CpvX2b8AGU5AKuCi1iDK X-Gm-Message-State: AOJu0Yw0jv4/KAo4xLMK76/fLolBaYZ6xqCphjwiGWeogl8nIBfMsMMW UcVl50UwZfGBqRQ5b7oiuqDFzEQ4hWjr3mD+Cql6/TO7BkbSpf5SM2gxkn0GvjGDExddl2dY/bX Ofw== X-Google-Smtp-Source: AGHT+IGH2cSIpCjJg5VVgi0MM3UOWFBb+tltx0R/3kd58Fx7yV5e38NRCJBGLw8haD00EsMwrzrM9fVPYi8= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:90b:50b:b0:2a5:366a:30fa with SMTP id r11-20020a17090b050b00b002a5366a30famr2077pjz.3.1712870501701; Thu, 11 Apr 2024 14:21:41 -0700 (PDT) Date: Thu, 11 Apr 2024 14:21:40 -0700 In-Reply-To: <20240126085444.324918-16-xiong.y.zhang@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240126085444.324918-1-xiong.y.zhang@linux.intel.com> <20240126085444.324918-16-xiong.y.zhang@linux.intel.com> Message-ID: Subject: Re: [RFC PATCH 15/41] KVM: x86/pmu: Manage MSR interception for IA32_PERF_GLOBAL_CTRL From: Sean Christopherson To: Xiong Zhang Cc: pbonzini@redhat.com, peterz@infradead.org, mizhang@google.com, kan.liang@intel.com, zhenyuw@linux.intel.com, dapeng1.mi@linux.intel.com, jmattson@google.com, kvm@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, zhiyuan.lv@intel.com, eranian@google.com, irogers@google.com, samantha.alt@intel.com, like.xu.linux@gmail.com, chao.gao@intel.com, Xiong Zhang Content-Type: text/plain; charset="us-ascii" On Fri, Jan 26, 2024, Xiong Zhang wrote: > + if (is_passthrough_pmu_enabled(&vmx->vcpu)) { > + /* > + * Setup auto restore guest PERF_GLOBAL_CTRL MSR at vm entry. > + */ > + if (vmentry_ctrl & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL) > + vmcs_write64(GUEST_IA32_PERF_GLOBAL_CTRL, 0); > + else { > + i = vmx_find_loadstore_msr_slot(&vmx->msr_autoload.guest, > + MSR_CORE_PERF_GLOBAL_CTRL); > + if (i < 0) { > + i = vmx->msr_autoload.guest.nr++; > + vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, > + vmx->msr_autoload.guest.nr); > + } > + vmx->msr_autoload.guest.val[i].index = MSR_CORE_PERF_GLOBAL_CTRL; > + vmx->msr_autoload.guest.val[i].value = 0; Eww, no. Just make cpu_has_load_perf_global_ctrl() and VM_EXIT_SAVE_IA32_PERF_GLOBAL_CTRL hard requirements for enabling passthrough mode. And then have clear_atomic_switch_msr() yell if KVM tries to disable loading MSR_CORE_PERF_GLOBAL_CTRL.