linux-kernel - Re: [PATCH v7 03/20] x86/virt/tdx: Disable TDX if X2APIC is not enabled

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Message-ID: <c564a7fe-2e33-a071-e333-39163471c678@intel.com>
Date:   Mon, 21 Nov 2022 16:44:50 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "Luck, Tony" <tony.luck@...el.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v7 03/20] x86/virt/tdx: Disable TDX if X2APIC is not
 enabled

On 11/21/22 16:30, Huang, Kai wrote:
> 
> How about still having a patch to make INTEL_TDX_HOST depend on X86_X2APIC but
> with something below in the changelog?
> 
> "
> TDX capable platforms are locked to X2APIC mode and cannot fall back to the
> legacy xAPIC mode when TDX is enabled by the BIOS.   It doesn't make sense to
> turn on INTEL_TDX_HOST while X86_X2APIC is not enabled.  Make INTEL_TDX_HOST
> depend on X86_X2APIC.

That's fine and it makes logical sense as a dependency.  TDX host
support requires x2APIC.  Period.