linux-kernel - Re: [PATCH 40/61] KVM: VMX: Convert feature updates from CPUID to KVM cpu caps

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Date:   Mon, 24 Feb 2020 22:40:00 +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 40/61] KVM: VMX: Convert feature updates from CPUID to KVM cpu caps

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

> Use the recently introduced KVM CPU caps to propagate VMX-only (kernel)
> settings to supported CPUID flags.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 51 ++++++++++++++++++++++++------------------
>  1 file changed, 29 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 11b9c1e7e520..bae915431c72 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7102,37 +7102,42 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
>  static void vmx_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
>  {
>  	switch (entry->function) {
> -	case 0x1:
> -		if (nested)
> -			cpuid_entry_set(entry, X86_FEATURE_VMX);
> -		break;
>  	case 0x7:
> -		if (boot_cpu_has(X86_FEATURE_MPX) && kvm_mpx_supported())
> -			cpuid_entry_set(entry, X86_FEATURE_MPX);
> -		if (boot_cpu_has(X86_FEATURE_INVPCID) && cpu_has_vmx_invpcid())
> -			cpuid_entry_set(entry, X86_FEATURE_INVPCID);
> -		if (boot_cpu_has(X86_FEATURE_INTEL_PT) &&
> -		    vmx_pt_mode_is_host_guest())
> -			cpuid_entry_set(entry, X86_FEATURE_INTEL_PT);
>  		if (vmx_umip_emulated())
>  			cpuid_entry_set(entry, X86_FEATURE_UMIP);
> -
> -		/* PKU is not yet implemented for shadow paging. */
> -		if (enable_ept && boot_cpu_has(X86_FEATURE_PKU) &&
> -		    boot_cpu_has(X86_FEATURE_OSPKE))
> -			cpuid_entry_set(entry, X86_FEATURE_PKU);
> -		break;
> -	case 0x80000001:
> -		if (!cpu_has_vmx_rdtscp())
> -			cpuid_entry_clear(entry, X86_FEATURE_RDTSCP);
> -		if (enable_ept && !cpu_has_vmx_ept_1g_page())
> -			cpuid_entry_clear(entry, X86_FEATURE_GBPAGES);
>  		break;
>  	default:
>  		break;
>  	}
>  }
>  

Same comment as for svm: I think someone may not understand what goes
where, i.e. the separation between vmx_set_supported_cpuid() and
vmx_set_cpu_caps().

> +static __init void vmx_set_cpu_caps(void)
> +{
> +	/* CPUID 0x1 */
> +	if (nested)
> +		kvm_cpu_cap_set(X86_FEATURE_VMX);
> +
> +	/* CPUID 0x7 */
> +	if (boot_cpu_has(X86_FEATURE_MPX) && kvm_mpx_supported())
> +		kvm_cpu_cap_set(X86_FEATURE_MPX);
> +	if (boot_cpu_has(X86_FEATURE_INVPCID) && cpu_has_vmx_invpcid())
> +		kvm_cpu_cap_set(X86_FEATURE_INVPCID);
> +	if (boot_cpu_has(X86_FEATURE_INTEL_PT) &&
> +	    vmx_pt_mode_is_host_guest())
> +		kvm_cpu_cap_set(X86_FEATURE_INTEL_PT);
> +
> +	/* PKU is not yet implemented for shadow paging. */
> +	if (enable_ept && boot_cpu_has(X86_FEATURE_PKU) &&
> +	    boot_cpu_has(X86_FEATURE_OSPKE))
> +		kvm_cpu_cap_set(X86_FEATURE_PKU);
> +
> +	/* CPUID 0x80000001 */
> +	if (!cpu_has_vmx_rdtscp())
> +		kvm_cpu_cap_clear(X86_FEATURE_RDTSCP);
> +	if (enable_ept && !cpu_has_vmx_ept_1g_page())
> +		kvm_cpu_cap_clear(X86_FEATURE_GBPAGES);
> +}
> +
>  static void vmx_request_immediate_exit(struct kvm_vcpu *vcpu)
>  {
>  	to_vmx(vcpu)->req_immediate_exit = true;
> @@ -7750,6 +7755,8 @@ static __init int hardware_setup(void)
>  			return r;
>  	}
>  
> +	vmx_set_cpu_caps();
> +
>  	r = alloc_kvm_area();
>  	if (r)
>  		nested_vmx_hardware_unsetup();

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

-- 
Vitaly