linux-kernel - Re: [PATCH] KVM: X86: Call kvm_x86_ops.cpuid

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Date:   Thu, 28 May 2020 17:22:57 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Xiaoyao Li <xiaoyao.li@...el.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        kvm@...r.kernel.org
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: X86: Call kvm_x86_ops.cpuid_update() after CPUIDs
 fully updated

On 28/05/20 17:19, Xiaoyao Li wrote:
> kvm_x86_ops.cpuid_update() is used to update vmx/svm settings based on
> updated CPUID settings. So it's supposed to be called after CPUIDs are
> fully updated, not in the middle stage.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>

Are you seeing anything bad happening from this?

Paolo

> ---
>  arch/x86/kvm/cpuid.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index cd708b0b460a..753739bc1bf0 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -208,8 +208,11 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
>  	vcpu->arch.cpuid_nent = cpuid->nent;
>  	cpuid_fix_nx_cap(vcpu);
>  	kvm_apic_set_version(vcpu);
> -	kvm_x86_ops.cpuid_update(vcpu);
>  	r = kvm_update_cpuid(vcpu);
> +	if (r)
> +		goto out;
> +
> +	kvm_x86_ops.cpuid_update(vcpu);
>  
>  out:
>  	vfree(cpuid_entries);
> @@ -231,8 +234,11 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
>  		goto out;
>  	vcpu->arch.cpuid_nent = cpuid->nent;
>  	kvm_apic_set_version(vcpu);
> -	kvm_x86_ops.cpuid_update(vcpu);
>  	r = kvm_update_cpuid(vcpu);
> +	if (r)
> +		goto out;
> +
> +	kvm_x86_ops.cpuid_update(vcpu);
>  out:
>  	return r;
>  }
>