linux-kernel - Re: [PATCH 52/61] KVM: x86: Use KVM cpu caps to detect MSR_TSC

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Message-ID: <87sgiylpxt.fsf@vitty.brq.redhat.com>
Date:   Tue, 25 Feb 2020 15:08:46 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 52/61] KVM: x86: Use KVM cpu caps to detect MSR_TSC_AUX virt support

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> Check for MSR_TSC_AUX virtualization via kvm_cpu_cap_has() and drop
> ->rdtscp_supported().
>
> Note, vmx_rdtscp_supported() needs to hang around a tiny bit longer due
> other usage in VMX code.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 1 -
>  arch/x86/kvm/svm.c              | 6 ------
>  arch/x86/kvm/vmx/vmx.c          | 3 ---
>  arch/x86/kvm/x86.c              | 2 +-
>  4 files changed, 1 insertion(+), 11 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 113b138a0347..1dd5ac8a2136 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1143,7 +1143,6 @@ struct kvm_x86_ops {
>  	int (*get_tdp_level)(struct kvm_vcpu *vcpu);
>  	u64 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
>  	int (*get_lpage_level)(void);
> -	bool (*rdtscp_supported)(void);
>  
>  	void (*set_tdp_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);
>  
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index f4434816dcdf..6dd9c810c0dc 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -6074,11 +6074,6 @@ static int svm_get_lpage_level(void)
>  	return PT_PDPE_LEVEL;
>  }
>  
> -static bool svm_rdtscp_supported(void)
> -{
> -	return boot_cpu_has(X86_FEATURE_RDTSCP);
> -}
> -
>  static bool svm_pt_supported(void)
>  {
>  	return false;
> @@ -7443,7 +7438,6 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
>  
>  	.cpuid_update = svm_cpuid_update,
>  
> -	.rdtscp_supported = svm_rdtscp_supported,
>  	.pt_supported = svm_pt_supported,
>  
>  	.set_supported_cpuid = svm_set_supported_cpuid,
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 2a1df1b714db..c3577f11f538 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7870,9 +7870,6 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {
>  	.get_lpage_level = vmx_get_lpage_level,
>  
>  	.cpuid_update = vmx_cpuid_update,
> -
> -	.rdtscp_supported = vmx_rdtscp_supported,
> -
>  	.set_supported_cpuid = vmx_set_supported_cpuid,
>  
>  	.has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index a6d5f22c7ef6..e4353c03269c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5246,7 +5246,7 @@ static void kvm_init_msr_list(void)
>  				continue;
>  			break;
>  		case MSR_TSC_AUX:
> -			if (!kvm_x86_ops->rdtscp_supported())
> +			if (!kvm_cpu_cap_has(X86_FEATURE_RDTSCP))
>  				continue;
>  			break;
>  		case MSR_IA32_RTIT_CTL:

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>

-- 
Vitaly