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Subject: Re: UBSAN: shift-out-of-bounds in kvm_vcpu_after_set_cpuid
To:     Sean Christopherson <seanjc@google.com>,
        Jim Mattson <jmattson@google.com>
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        LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        the arch/x86 maintainers <x86@kernel.org>
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From:   Paolo Bonzini <pbonzini@redhat.com>
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Date:   Tue, 12 Jan 2021 09:06:07 +0100
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On 12/01/21 00:01, Sean Christopherson wrote:
>> Perhaps cpuid_query_maxphyaddr() should just look at the low 5 bits of
>> CPUID.80000008H:EAX?

The low 6 bits I guess---yes, that would make sense and it would have 
also fixed the bug.

(Nevertheless it's a good idea to make rsvd_bits more robust as well, as 
in the commit that Sean referenced.

Paolo