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Subject: Re: [PATCH v4] KVM: x86: Fix KVM_GET_CPUID2 ioctl to return cpuid
 entries count
To:     "Denis V. Lunev" <den@openvz.org>,
        Sean Christopherson <seanjc@google.com>,
        Valeriy Vdovin <valeriy.vdovin@virtuozzo.com>
Cc:     linux-kernel@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Shuah Khan <shuah@kernel.org>,
        Aaron Lewis <aaronlewis@google.com>,
        Alexander Graf <graf@amazon.com>,
        Andrew Jones <drjones@redhat.com>,
        Oliver Upton <oupton@google.com>,
        Like Xu <like.xu@linux.intel.com>, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org
References: <20210428172729.3551-1-valeriy.vdovin@virtuozzo.com>
 <YIoFFl72VSeuhCRt@google.com>
 <0d68dbc3-8462-7763-fbad-f3b895fcf6e6@redhat.com>
 <be7eedf7-03a2-f998-079d-b18101b8b187@openvz.org>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <63e54361-0018-ad3b-fb2b-e5dba6a0f221@redhat.com>
Date:   Tue, 4 May 2021 09:23:05 +0200
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On 03/05/21 21:18, Denis V. Lunev wrote:
> On 5/3/21 5:54 PM, Paolo Bonzini wrote:
>> On 29/04/21 03:00, Sean Christopherson wrote:
>>> On Wed, Apr 28, 2021, Valeriy Vdovin wrote:
>>>> It's very explicit by the code that it was designed to receive some
>>>> small number of entries to return E2BIG along with the corrected
>>>> number.
>>>
>>> LOL, saying KVM_GET_CPUID2 was "designed" is definitely giving the KVM
>>> forefathers the benefit of the doubt.
>>
>> I was going to make a different joke, i.e. that KVM_GET_CPUID2 was
>> indeed designed the way Valeriy described, but that design was
>> forgotten soon after.
>>
>> Really, this ioctl has been such a trainwreck that I think the only
>> good solution here is to drop it.
>>
>> Paolo
>>
> 
> should we discuss KVM_GET_CPUID3 which will work "normally"?

Is anybody using KVM_GET_CPUID2 at all?

Paolo