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Message-ID: <82D7661F83C1A047AF7DC287873BF1E167E504FC@SHSMSX101.ccr.corp.intel.com> Date: Mon, 4 Dec 2017 01:21:20 +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>, Chao Peng <chao.p.peng@...ux.intel.com> Subject: RE: [PATCH v3 7/9] KVM: x86: Implement Intel Processor Trace MSRs read/write > >>> + case MSR_IA32_RTIT_ADDR0_A ... MSR_IA32_RTIT_ADDR3_B: { > >>> + u32 eax, ebx, ecx, edx; > >>> + > >>> + cpuid_count(0x14, 1, &eax, &ebx, &ecx, &edx); > >> > >> Please cache the cpuid_count result, or do the cpuid_count after testing > >> vmx_pt_supported() (which you can use instead of going through kvm_x86_ops). > > > > Hi Paolo, > > Thanks for your reply. I have cache EAX in "struct pt_desc" and will initialize in vmx_vcpu_setup(). > > +struct pt_desc { > > + unsigned int addr_num; > > + struct pt_ctx host; > > + struct pt_ctx guest; > > +}; > > But kvm_init_msr_list() is invoked too early, I have to read from hardware. So, what about change like this. > > > > - cpuid_count(0x14, 1, &eax, &ebx, &ecx, &edx); > > - if (!kvm_x86_ops->pt_supported() || msrs_to_save[i] - > > - MSR_IA32_RTIT_ADDR0_A >= (eax & 0x7)) > > + if (!kvm_x86_ops->pt_supported()) > > continue; > > + cpuid_count(0x14, 1, &eax, &ebx, &ecx, &edx); > > + if (msrs_to_save[i] - > > + MSR_IA32_RTIT_ADDR0_A >= (eax & 0x7)) > > + continue; > > For kvm_init_msr_list it's okay. But can you please add a > pt_msr_count() function? > Of course, I will fix in next version. Thanks! Luwei Kang > >> > >>> + if (!kvm_x86_ops->pt_supported() || msrs_to_save[i] - > >>> + MSR_IA32_RTIT_ADDR0_A >= (eax & 0x7)) > >>> + continue; > >>> + break; > >
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