linux-kernel - Re: [PATCH v5 2/3] KVM: vmx: Emulate MSR IA32_UMWAIT

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Date:   Wed, 3 Jul 2019 08:29:54 +0800
From:   Tao Xu <tao3.xu@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Xiaoyao Li <xiaoyao.li@...ux.intel.com>, rkrcmar@...hat.com,
        corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        hpa@...or.com, sean.j.christopherson@...el.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        fenghua.yu@...el.com, jingqi.liu@...el.com
Subject: Re: [PATCH v5 2/3] KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL

On 7/3/2019 12:37 AM, Paolo Bonzini wrote:
> On 20/06/19 11:46, Xiaoyao Li wrote:
>> You cannot put the atomic switch here. What if umwait_control_cached is changed
>> at runtime? Host kernel patch exposed a sysfs interface to let it happen.
> 
> Thanks for the review, Xiaoyao.  I agree with both of your remarks.
> 
> Paolo
> 
Hi paolo,

The issues have been solved in v6 patches, could you help to review v6 
patches?

Thanks

Tao

>>> +		break;
>>>   	case MSR_IA32_SPEC_CTRL:
>>>   		if (!msr_info->host_initiated &&
>>>   		    !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL))
>>> @@ -4126,6 +4148,8 @@ 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);
>>> 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/kvm/x86.c b/arch/x86/kvm/x86.c
>>> index 83aefd759846..4480de459bf4 100644
>>> --- a/arch/x86/kvm/x86.c
>>> +++ b/arch/x86/kvm/x86.c
>>> @@ -1138,6 +1138,7 @@ static u32 msrs_to_save[] = {
>>>   	MSR_IA32_RTIT_ADDR1_A, MSR_IA32_RTIT_ADDR1_B,
>>>   	MSR_IA32_RTIT_ADDR2_A, MSR_IA32_RTIT_ADDR2_B,
>>>   	MSR_IA32_RTIT_ADDR3_A, MSR_IA32_RTIT_ADDR3_B,
>>> +	MSR_IA32_UMWAIT_CONTROL,
>>>   };
>>>   
>>>   static unsigned num_msrs_to_save;
>>
>