Re: [pve-devel] [PATCH qemu-server v2 3/3] Add support for Intel TDX

[Anton Iacobaeus <anton.iacobaeus@canarybit.eu>]

On 10/13/25 11:30, Fiona Ebner wrote:
> Am 08.10.25 um 12:21 PM schrieb Fiona Ebner:
>> Am 04.10.25 um 3:23 PM schrieb Anton Iacobaeus:
>>> From: Philipp Giersfeld <philipp.giersfeld@canarybit.eu>
>>>
>>> This commit adds support for setting up an Intel TDX VM. A Intel TDX VM
>>> can be setup similar to AMD SEV but uses a different firmware image.
>>>
>>> Signed-off-by: Philipp Giersfeld <philipp.giersfeld@canarybit.eu>
>>> Signed-off-by: Anton Iacobaeus <anton.iacobaeus@canarybit.eu>
>>
>> Apart from a few nits, see below:
>> Reviewed-by: Fiona Ebner <f.ebner@proxmox.com>
>>> @@ -3965,6 +3978,10 @@ sub config_to_command {
>>>       if ($conf->{'amd-sev'}) {
>>>           push @$devices, '-object', get_amd_sev_object($conf->{'amd-sev'}, $conf->{bios});
>>>           push @$machineFlags, 'confidential-guest-support=sev0';
>>> +    } elsif ($conf->{'intel-tdx'}) {
>>> +        push @$devices, '-object', get_intel_tdx_object($conf->{'intel-tdx'}, $conf->{bios});
>>> +        push @$machineFlags, 'confidential-guest-support=tdx0';
>>> +        push @$machineFlags, 'kernel_irqchip=split';
> 
> One more thing I noticed/remembered:
> 
> Don't we also need something like
> -device vhost-vsock-pci,guest-cid=3
> 
> for communication between QGS and TD VM like described in the docs:
> https://cc-enabling.trustedservices.intel.com/intel-tdx-enabling-guide/05/host_os_setup/#setup-communication-path-between-qgs-and-td
> 
> ?
Yes you are correct, but it is only required for attestation support,
which was initially out of scope for this series. The changes are
however quite small and they could fit in this series.

Note that TDX memory encryption works without any communication between
the QGS and TD VM. The QGS is only contacted for quote generation.

In terms of this particular device, it was only used in TDX Early
Preview. Today a quote-generation-socket should instead be included
directly in the TDX object, like this:
-object 
'{"qom-type":"tdx-guest","id":"tdx","quote-generation-socket":{"type": 
"vsock", "cid":"2","port":"4050"}}'

I think this change can be included in this series, but it adds some
additional scope since the type, cid and port can be configured
differently from these defaults.

> 
>>
>> Nit: would be nice to have a comment describing the rationale behind the
>> kernel_irqchip option and/or a sentence in the commit message.
>>
>>>       }
>>>   
>>>       PVE::QemuServer::Virtiofs::config($conf, $vmid, $devices);
> 
Yes indeed, I will add that.

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