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Subject: Re: [PATCH 3/4] KVM: x86: WARN and reject loading KVM if NX is
 supported but not enabled
To:     Jim Mattson <jmattson@google.com>,
        Sean Christopherson <seanjc@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>
References: <20210615164535.2146172-1-seanjc@google.com>
 <20210615164535.2146172-4-seanjc@google.com>
 <CALMp9eSkVaDfCJwW1eds=7H7yn2pKJPKoFVpc1GQcEqGD5S0Dg@mail.gmail.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <6ea2385a-9abe-82b8-6c57-8dc3aac824b2@redhat.com>
Date:   Fri, 18 Jun 2021 12:27:27 +0200
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On 16/06/21 00:39, Jim Mattson wrote:
>>
>>          rdmsrl_safe(MSR_EFER, &host_efer);
>> +       if (WARN_ON_ONCE(boot_cpu_has(X86_FEATURE_NX) &&
>> +                        !(host_efer & EFER_NX)))
>> +               return -EIO;
> Input/output error? Is that really the most appropriate error here?
> Why not, say, -ENOTSUP?
> 
> I'm sure there's some arcane convention here that I'm not privy to.:-)
> 
> Reviewed-by: Jim Mattson<jmattson@google.com>
> 

EIO often means "how the heck did we get here?" or "look in dmesg to get 
more info", both of which I think are appropriate after a WARN.

Paolo