From:   Thomas Gleixner <tglx@linutronix.de>
To:     isaku.yamahata@intel.com, Ingo Molnar <mingo@redhat.com>,
        Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, erdemaktas@google.com,
        Connor Kuehl <ckuehl@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc:     isaku.yamahata@intel.com, isaku.yamahata@gmail.com,
        Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: [RFC PATCH v3 23/59] KVM: x86: Allow host-initiated WRMSR to
 set X2APIC regardless of CPUID
In-Reply-To: <63556f13e9608cbccf97d356be46a345772d76d3.1637799475.git.isaku.yamahata@intel.com>
References: <cover.1637799475.git.isaku.yamahata@intel.com>
 <63556f13e9608cbccf97d356be46a345772d76d3.1637799475.git.isaku.yamahata@intel.com>
Date:   Thu, 25 Nov 2021 20:41:48 +0100
Message-ID: <87fsrkja4j.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Wed, Nov 24 2021 at 16:20, isaku yamahata wrote:
> Let userspace, or in the case of TDX, KVM itself, enable X2APIC even if
> X2APIC is not reported as supported in the guest's CPU model.  KVM
> generally does not force specific ordering between ioctls(), e.g. this
> forces userspace to configure CPUID before MSRs.  And for TDX, vCPUs
> will always run with X2APIC enabled, e.g. KVM will want/need to enable
> X2APIC from time zero.

This is complete crap. Fix the broken user space and do not add
horrible hacks to the kernel.

Thanks,

        tglx