linux-kernel - Re: [PATCH 3/6] KVM: x86: Add dedicated emulator helper for grabbing CPUID.maxphyaddr

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Date:   Tue, 3 Mar 2020 18:21:10 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Vitaly Kuznetsov <vkuznets@...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, Jan Kiszka <jan.kiszka@...mens.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: Re: [PATCH 3/6] KVM: x86: Add dedicated emulator helper for grabbing
 CPUID.maxphyaddr

On 03/03/20 17:28, Sean Christopherson wrote:
>> I don't think this is a particularly useful change.  Yes, it's not
>> intuitive but is it more than a matter of documentation (and possibly
>> moving the check_cr_write snippet into a separate function)?
> 
> I really don't like duplicating the maxphyaddr logic.  I'm paranoid
> something will come along and change the "effective" maxphyaddr and we'll
> forget all about the emulator, e.g. SEV, TME and paravirt XO all dance
> around maxphyaddr.

Well, I'm paranoid about breaking everything else... :)

Adding a separate emulator_get_maxphyaddr function would at least
simplify grepping, since searching for 0x80000008 isn't exactly intuitive.

Paolo