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[209.132.180.67]) by mx.google.com with ESMTP id a64si3860002pla.432.2019.06.17.20.05.04; Mon, 17 Jun 2019 20:05:19 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727159AbfFRDE7 (ORCPT + 99 others); Mon, 17 Jun 2019 23:04:59 -0400 Received: from mga07.intel.com ([134.134.136.100]:60266 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725829AbfFRDE7 (ORCPT ); Mon, 17 Jun 2019 23:04:59 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Jun 2019 20:04:58 -0700 X-ExtLoop1: 1 Received: from txu2-mobl.ccr.corp.intel.com (HELO [10.239.196.224]) ([10.239.196.224]) by orsmga003.jf.intel.com with ESMTP; 17 Jun 2019 20:04:55 -0700 Subject: Re: [PATCH RESEND v3 2/3] KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL To: Xiaoyao Li , pbonzini@redhat.com, rkrcmar@redhat.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, sean.j.christopherson@intel.com, fenghua.yu@intel.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, jingqi.liu@intel.com References: <20190616095555.20978-1-tao3.xu@intel.com> <20190616095555.20978-3-tao3.xu@intel.com> From: Tao Xu Message-ID: <3468075c-9289-b2b5-8310-e1f39524a8e9@intel.com> Date: Tue, 18 Jun 2019 11:04:54 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/17/2019 11:32 AM, Xiaoyao Li wrote: > > > On 6/16/2019 5:55 PM, Tao Xu wrote: >> UMWAIT and TPAUSE instructions use IA32_UMWAIT_CONTROL at MSR index E1H >> to determines the maximum time in TSC-quanta that the processor can >> reside >> in either C0.1 or C0.2. >> >> This patch emulates MSR IA32_UMWAIT_CONTROL in guest and differentiate >> IA32_UMWAIT_CONTROL between host and guest. The variable >> mwait_control_cached in arch/x86/power/umwait.c caches the MSR value, so >> this patch uses it to avoid frequently rdmsr of IA32_UMWAIT_CONTROL. >> >> Co-developed-by: Jingqi Liu >> Signed-off-by: Jingqi Liu >> Signed-off-by: Tao Xu >> --- >>   arch/x86/kvm/vmx/vmx.c  | 36 ++++++++++++++++++++++++++++++++++++ >>   arch/x86/kvm/vmx/vmx.h  |  3 +++ >>   arch/x86/power/umwait.c |  3 ++- >>   3 files changed, 41 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >> index b35bfac30a34..f33a25e82cb8 100644 >> --- a/arch/x86/kvm/vmx/vmx.c >> +++ b/arch/x86/kvm/vmx/vmx.c >> @@ -1679,6 +1679,12 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, >> struct msr_data *msr_info) >>   #endif >>       case MSR_EFER: >>           return kvm_get_msr_common(vcpu, msr_info); >> +    case MSR_IA32_UMWAIT_CONTROL: >> +        if (!vmx_waitpkg_supported()) >> +            return 1; >> + >> +        msr_info->data = vmx->msr_ia32_umwait_control; >> +        break; >>       case MSR_IA32_SPEC_CTRL: >>           if (!msr_info->host_initiated && >>               !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL)) >> @@ -1841,6 +1847,15 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, >> struct msr_data *msr_info) >>               return 1; >>           vmcs_write64(GUEST_BNDCFGS, data); >>           break; >> +    case MSR_IA32_UMWAIT_CONTROL: >> +        if (!vmx_waitpkg_supported()) >> +            return 1; >> + >> +        if (!data) >> +            break; >> + > > Why cannot clear it to zero? > After read the kernel code of umwait again and test it again, host can set it to 0, when we set sys max_time to 0. So I am wondering to remove the "if (!data)" and set the value of msr value to 0x186a0(maxtime = 100000) when KVM initialization. And considering we use "-overcommit cpu-pm=on" to use umwait in QEMU side. It means guest can over-commit the host CPU, so set to 0 make sense. >> +        vmx->msr_ia32_umwait_control = data; >> +        break; >>       case MSR_IA32_SPEC_CTRL: >>           if (!msr_info->host_initiated && >>               !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL)) >> @@ -4126,6 +4141,8 @@ static void vmx_vcpu_reset(struct kvm_vcpu >> *vcpu, bool init_event) >>       vmx->rmode.vm86_active = 0; >>       vmx->spec_ctrl = 0; >> +    vmx->msr_ia32_umwait_control = 0; >> + >>       vcpu->arch.microcode_version = 0x100000000ULL; >>       vmx->vcpu.arch.regs[VCPU_REGS_RDX] = get_rdx_init_val(); >>       kvm_set_cr8(vcpu, 0); >> @@ -6339,6 +6356,23 @@ static void atomic_switch_perf_msrs(struct >> vcpu_vmx *vmx) >>                       msrs[i].host, false); >>   } >> +static void atomic_switch_ia32_umwait_control(struct vcpu_vmx *vmx) >> +{ >> +    u64 host_umwait_control; >> + >> +    if (!vmx_waitpkg_supported()) >> +        return; >> + >> +    host_umwait_control = umwait_control_cached; >> + > > It's redundant to define host_umwait_control and this line, we can just > use umwait_control_cached. Thanks for reminding. > >> +    if (vmx->msr_ia32_umwait_control != host_umwait_control) >> +        add_atomic_switch_msr(vmx, MSR_IA32_UMWAIT_CONTROL, >> +                      vmx->msr_ia32_umwait_control, >> +                      host_umwait_control, false); > > The bit 1 is reserved, at least, we need to do below to ensure not > modifying the reserved bit: > >     guest_val = (vmx->msr_ia32_umwait_control & ~BIT_ULL(1)) | >             (host_val & BIT_ULL(1)) > >> +    else >> +        clear_atomic_switch_msr(vmx, MSR_IA32_UMWAIT_CONTROL); >> +} >> + >>   static void vmx_arm_hv_timer(struct vcpu_vmx *vmx, u32 val) >>   { >>       vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, val); >> @@ -6447,6 +6481,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) >>       atomic_switch_perf_msrs(vmx); >> +    atomic_switch_ia32_umwait_control(vmx); >> + >>       vmx_update_hv_timer(vcpu); >>       /* >> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h >> index 61128b48c503..8485bec7c38a 100644 >> --- a/arch/x86/kvm/vmx/vmx.h >> +++ b/arch/x86/kvm/vmx/vmx.h >> @@ -14,6 +14,8 @@ >>   extern const u32 vmx_msr_index[]; >>   extern u64 host_efer; >> +extern u32 umwait_control_cached; >> + >>   #define MSR_TYPE_R    1 >>   #define MSR_TYPE_W    2 >>   #define MSR_TYPE_RW    3 >> @@ -194,6 +196,7 @@ struct vcpu_vmx { >>   #endif >>       u64              spec_ctrl; >> +    u64              msr_ia32_umwait_control; >>       u32 vm_entry_controls_shadow; >>       u32 vm_exit_controls_shadow; >> diff --git a/arch/x86/power/umwait.c b/arch/x86/power/umwait.c >> index 7fa381e3fd4e..2e6ce4cbccb3 100644 >> --- a/arch/x86/power/umwait.c >> +++ b/arch/x86/power/umwait.c >> @@ -9,7 +9,8 @@ >>    * MSR value. By default, umwait max time is 100000 in TSC-quanta >> and C0.2 >>    * is enabled >>    */ >> -static u32 umwait_control_cached = 100000; >> +u32 umwait_control_cached = 100000; >> +EXPORT_SYMBOL_GPL(umwait_control_cached); >>   /* >>    * Serialize access to umwait_control_cached and IA32_UMWAIT_CONTROL >> MSR >>