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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>
 <63e54361-0018-ad3b-fb2b-e5dba6a0f221@redhat.com>
 <048b3f3a-379d-cff3-20b6-fc74dd12a98f@openvz.org>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <514b5373-c07b-ad34-5fba-f8850faf6d68@redhat.com>
Date:   Tue, 4 May 2021 10:21:47 +0200
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On 04/05/21 10:15, Denis V. Lunev wrote:
> As far as I understand only some testing within kernel now.
> Though we have plans to expose it for QAPI as the series
> in QEMU
>    [PATCH 1/2] qapi: fix error handling for x-vz-query-cpu-model-cpuid
>    [PATCH 2/2] qapi: blacklisted x-vz-query-cpu-model-cpuid in tests
> is not coming in a good way.
> The idea was to avoid manual code rework in QEMU and
> expose collected model at least for debug.

KVM_GET_CPUID2 as a VM ioctl cannot expose the whole truth about CPUID 
either, since it doesn't handle the TSX_CTRL_CPUID_CLEAR bit.  Given 
that QEMU doesn't need KVM_GET_CPUID2; it only needs to save whatever it 
passed to KVM_SET_CPUID2.

Paolo