linux-kernel - Re: [PATCH v10 05/16] x86/virt/tdx: Add skeleton to enable TDX on demand

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Message-ID: <902b0166-6156-8def-a7a3-f0ce8995fa9c@intel.com>
Date:   Mon, 13 Mar 2023 22:45:45 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Isaku Yamahata <isaku.yamahata@...il.com>,
        "Huang, Kai" <kai.huang@...el.com>
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Luck, Tony" <tony.luck@...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 v10 05/16] x86/virt/tdx: Add skeleton to enable TDX on
 demand

On 3/13/23 21:02, Isaku Yamahata wrote:
>> Then it is a hidden behaviour of the TDX module that is not reflected in the
>> spec.  I am not sure whether we should handle because: 
>>
>> 1) This is an extremely rare case.  Kernel would be basically under attack if
>> such error happened.  In the current series we don't handle such case in
>> KEY.CONFIG either but just leave a comment (see patch 13).
>>
>> 2) Not sure whether this will be changed in the future.
>>
>> So I think we should keep as is.
> TDX 1.5 spec introduced TDX_RND_NO_ENTROPY status code.  For TDX 1.0, let's
> postpone it to TDX 1.5 activity.

What the heck does this mean?

I don't remember seeing any code here that checks for "TDX 1.0" or "TDX
1.5".  That means that this code needs to work with _any_ TDX version.

Are features being added to new versions that break code written for old
versions?