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Subject: Re: [PATCH 2/6] KVM: x86: Fix CPUID range check for Centaur and
 Hypervisor ranges
To:     Sean Christopherson <sean.j.christopherson@intel.com>,
        Jim Mattson <jmattson@google.com>
Cc:     Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Joerg Roedel <joro@8bytes.org>, kvm list <kvm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Jan Kiszka <jan.kiszka@siemens.com>,
        Xiaoyao Li <xiaoyao.li@intel.com>
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 <20200303045838.GF27842@linux.intel.com>
 <CALMp9eSYZKUBko4ZViNbasRGJs2bAO2fREHX9maDbLrYj8yDhQ@mail.gmail.com>
 <20200303180122.GO1439@linux.intel.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <41235370-c095-6d8a-2546-be88b3974bfe@redhat.com>
Date:   Wed, 4 Mar 2020 12:18:12 +0100
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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