linux-kernel - RE: [PATCH v2 00/21] Runtime TDX Module update support

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Message-ID: <IA1PR11MB9495837A621D8F0C7DB8F2D5E7E9A@IA1PR11MB9495.namprd11.prod.outlook.com>
Date: Thu, 16 Oct 2025 06:48:04 +0000
From: "Reshetova, Elena" <elena.reshetova@...el.com>
To: "Annapurve, Vishal" <vannapurve@...gle.com>
CC: "Gao, Chao" <chao.gao@...el.com>, "linux-coco@...ts.linux.dev"
	<linux-coco@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org>, "Chatre,
 Reinette" <reinette.chatre@...el.com>, "Weiny, Ira" <ira.weiny@...el.com>,
	"Huang, Kai" <kai.huang@...el.com>, "Williams, Dan J"
	<dan.j.williams@...el.com>, "yilun.xu@...ux.intel.com"
	<yilun.xu@...ux.intel.com>, "sagis@...gle.com" <sagis@...gle.com>,
	"paulmck@...nel.org" <paulmck@...nel.org>, "nik.borisov@...e.com"
	<nik.borisov@...e.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
	<dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar
	<mingo@...hat.com>, "Kirill A. Shutemov" <kas@...nel.org>, Paolo Bonzini
	<pbonzini@...hat.com>, "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: RE: [PATCH v2 00/21] Runtime TDX Module update support



> -----Original Message-----
> From: Vishal Annapurve <vannapurve@...gle.com>
> Sent: Wednesday, October 15, 2025 5:19 PM
> To: Reshetova, Elena <elena.reshetova@...el.com>
> Cc: Gao, Chao <chao.gao@...el.com>; linux-coco@...ts.linux.dev; linux-
> kernel@...r.kernel.org; x86@...nel.org; Chatre, Reinette
> <reinette.chatre@...el.com>; Weiny, Ira <ira.weiny@...el.com>; Huang, Kai
> <kai.huang@...el.com>; Williams, Dan J <dan.j.williams@...el.com>;
> yilun.xu@...ux.intel.com; sagis@...gle.com; paulmck@...nel.org;
> nik.borisov@...e.com; Borislav Petkov <bp@...en8.de>; Dave Hansen
> <dave.hansen@...ux.intel.com>; H. Peter Anvin <hpa@...or.com>; Ingo Molnar
> <mingo@...hat.com>; Kirill A. Shutemov <kas@...nel.org>; Paolo Bonzini
> <pbonzini@...hat.com>; Edgecombe, Rick P <rick.p.edgecombe@...el.com>;
> Thomas Gleixner <tglx@...utronix.de>
> Subject: Re: [PATCH v2 00/21] Runtime TDX Module update support
> 
> On Wed, Oct 15, 2025 at 1:54 AM Reshetova, Elena
> <elena.reshetova@...el.com> wrote:
> >
> >
> > > On Tue, Sep 30, 2025 at 7:54 PM Chao Gao <chao.gao@...el.com> wrote:
> > > >
> > > > === TDX Module Distribution Model ===
> > > >
> > > > At a high level, Intel publishes all TDX Modules on the github [2], along
> > > > with a mapping_file.json which documents the compatibility information
> > > > about each TDX Module and a userspace tool to install the TDX Module.
> OS
> > >
> > > [2] mentions about a limitation of doing runtime TDX module update:
> > >
> > > "Performing TD Preserving during a TD Build operation might result in
> > > a corrupted TD hash in the TD attestation report. Until fixed in a
> > > future Intel TDX module update, a host VMM can avoid the problem by
> > > not conducting a TD Preserving Update while TD Build operation is in
> > > progress."
> > >
> > > Do you know if this issue is fixed already? If so, what version of TDX
> > > module fixes this issue?
> >
> > It is not fixed, because the limitation comes from the internal crypto context
> > maintained by the IPP crypto library. Different versions of TDX module can
> > use different versions of IPP library (as any good SW that aims to take latest
> and
> > greatest version of its dependencies) and IPP library (as any library) does not
> > provide any compatibility guarantees on its runtime data structures.
> > So, the problem can show up if the old and new TDX module (prior and post
> > TD preserving update) use different IPP versions and IPP happened to change
> > internal data structure format in between these versions. There is nothing
> > TDX module can really do in this case.
> > But the situation can be avoided fully, if TD preserving update is not
> conducted
> > during the TD build time.
> 
> Few questions:
> 1) How is TD build time defined in this scenario?

TD build that has started by TDH.MNG.INIT will end must end by TDH.MR.FINALIZE
or by tearing down the TD; otherwise the TDX module will still count it as in-progress.

Best Regards,
Elena.