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

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Message-ID: <badc1c1118dab8ffd182348bf7117b7b58d3be66.camel@intel.com>
Date:   Tue, 22 Nov 2022 00:58:14 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "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>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "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 Mon, 2022-11-21 at 16:44 -0800, Dave Hansen wrote:
> 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.
> 
Thanks.  Perhaps I can reuse your second sentence 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.  TDX host support requires
x2APIC.  Make INTEL_TDX_HOST depend on X86_X2APIC.
"