Re: TDX migration model

[Artem Bityutskiy <dedekind1@gmail.com>]

[I dropped a bunch of people from CC, sorry about that, just restored the CC
list]

On Thu, 2026-11-05 at 08:58 -0600, Serge Hallyn (AMD) wrote:
> On Wed, Nov 04, 2026 at 03:51:45PM +0200, Artem Bityutskiy wrote:
> > Hi Peter, community,
> > 
> > Here is the TDX migration model doc that I mentioned in the CoCo migration
> > uAPI thread:
> > 
> > https://github.com/dedekind/dedekind-share/blob/master/2026/tdx-live-migration.md
> > 
> > The doc focuses on TDX only. It does not cover CoCo in general or
> > Linux/KVM. 
> > 
> > The goal is to lay out what the TDX module offers in terms of ABI and
> > migration flow today. Hopefully it is easier to read than the TDX specs,
> > which are much more detailed. Feedback is very welcome.
> > 
> > The uAPIs that we suggested were modeled around this flow and ABI. But
> > we kept general CoCo VMs in mind as much as we could.
> > 
> > The TDX live migration PoC implementation that we mentioned earlier follows
> > the flows and uses the ABIs described in the doc.
> > 
> > Thanks!
> > 
> > P.S. From the ARM talk and hallway conversations at Plumbers, I understood
> > that the ARM live migration flow is very similar to TDX. For SNP guests, we
> > have not heard enough yet.
> > 
> > Thanks,
> > Artem.
> 
> Thanks, Artem!
> 
> So, looking at the section '### How the Setup Session Works', is it safe
> to assume that you are using the qemu migration fd for the message
> transfers?  So basically qemu loops over KVM_MIGRATE_SETUP calls, which
> is directed to platform-specific handlers, which in the tdx case calls
> TDH.MIG.SETUP, and this loop continues until TDX_SUCCESS?  If so, great,
> that mirrors pretty exactly what we were looking at for SNP.

Hi,

Yes, that's the flow. I’m not sure about the migration fd part, I believe we
pass the setup session data via ioctl buffers. I am sure Kishen will can
clarify.

Thanks,
Artem.