linux-kernel - Re: [PATCH v4] KVM: x86: Fix KVM_GET_CPUID2 ioctl to return cpuid entries count

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Date:   Mon, 3 May 2021 22:18:06 +0300
From:   "Denis V. Lunev" <den@...nvz.org>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Valeriy Vdovin <valeriy.vdovin@...tuozzo.com>
Cc:     linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Shuah Khan <shuah@...nel.org>,
        Aaron Lewis <aaronlewis@...gle.com>,
        Alexander Graf <graf@...zon.com>,
        Andrew Jones <drjones@...hat.com>,
        Oliver Upton <oupton@...gle.com>,
        Like Xu <like.xu@...ux.intel.com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4] KVM: x86: Fix KVM_GET_CPUID2 ioctl to return cpuid
 entries count

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"?

Den