linux-kernel - Re: [PATCH 24/61] KVM: x86: Drop explicit @func param from ->set_supported

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Message-ID: <87blpsq79x.fsf@vitty.brq.redhat.com>
Date:   Fri, 21 Feb 2020 16:39:22 +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 24/61] KVM: x86: Drop explicit @func param from ->set_supported_cpuid()

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

> Drop the explicit @func param from ->set_supported_cpuid() and instead
> pull the CPUID function from the relevant entry.  This sets the stage
> for hardening guest CPUID updates in future patches, e.g. allows adding
> run-time assertions that the CPUID feature being changed is actually
> a bit in the referenced CPUID entry.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 2 +-
>  arch/x86/kvm/cpuid.c            | 2 +-
>  arch/x86/kvm/svm.c              | 4 ++--
>  arch/x86/kvm/vmx/vmx.c          | 4 ++--
>  4 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 85f0d96cfeb2..a61928d5435b 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1148,7 +1148,7 @@ struct kvm_x86_ops {
>  
>  	void (*set_tdp_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);
>  
> -	void (*set_supported_cpuid)(u32 func, struct kvm_cpuid_entry2 *entry);
> +	void (*set_supported_cpuid)(struct kvm_cpuid_entry2 *entry);
>  
>  	bool (*has_wbinvd_exit)(void);
>  
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 056faf27b14b..e3026fe638aa 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -784,7 +784,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
>  		break;
>  	}
>  
> -	kvm_x86_ops->set_supported_cpuid(function, entry);
> +	kvm_x86_ops->set_supported_cpuid(entry);
>  
>  	r = 0;
>  
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 3c7ddaff405d..535eb746fb0f 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -6032,9 +6032,9 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu)
>  
>  #define F feature_bit
>  
> -static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
> +static void svm_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
>  {
> -	switch (func) {
> +	switch (entry->function) {
>  	case 0x1:
>  		if (avic)
>  			entry->ecx &= ~F(X2APIC);
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 98fd651f7f7e..3ff830e2258e 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7104,9 +7104,9 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
>  	}
>  }
>  
> -static void vmx_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
> +static void vmx_set_supported_cpuid(struct kvm_cpuid_entry2 *entry)
>  {
> -	if (func == 1 && nested)
> +	if (entry->function == 1 && nested)
>  		entry->ecx |= feature_bit(VMX);
>  }

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

-- 
Vitaly