linux-kernel - Re: [PATCH 2/6] KVM: x86: Fix CPUID range check for Centaur and Hypervisor ranges

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Date:   Wed, 4 Mar 2020 12:18:12 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Jim Mattson <jmattson@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH 2/6] KVM: x86: Fix CPUID range check for Centaur and
 Hypervisor ranges

On 03/03/20 19:01, Sean Christopherson wrote:
> static bool cpuid_function_in_range(struct kvm_vcpu *vcpu, u32 function)
> {
> 	struct kvm_cpuid_entry2 *max;
> 
> 	if (function >= 0x40000000 && function <= 0x4fffffff)
> 		max = kvm_find_cpuid_entry(vcpu, function & 0xffffff00, 0);
> 	else
> 		max = kvm_find_cpuid_entry(vcpu, function & 0x80000000, 0);
> 	return max && function <= max->eax;
> }

Yes, this is a good idea (except it should be & 0xc0000000 to cover
Centaur).

Paolo