Re: [PATCH 0/5] iommu/vt-d: Introduce trusted DMA initialization support

[Baolu Lu <baolu.lu@linux.intel.com>]

On 9/18/2026 10:30 AM, Tian, Kevin wrote:
>> From: Lu Baolu <baolu.lu@linux.intel.com>
>> Sent: Tuesday, September 15, 2026 3:42 PM
>>
>> Hi,
>>
>> This series adds Intel VT-d trusted extension support to the host Intel
>> IOMMU driver as groundwork for TEE I/O trusted DMA (e.g. TDX Connect).
>>
>> The trusted extension introduces a parallel, extension-specific path for
>> trusted DMA assets used by confidential device assignment. Existing VT-d
>> functionality remains unchanged for regular host DMA paths.
>>
>>  From the TDX Connect architecture perspective, VT-d is enhanced with:
>>
>>    1) Trusted DMA translation root table
>>       - A second root-table address register, restricted to SEAM SAI.
>>       - Programmed by the TDX module with the root of TDX-managed DMA
>>         translation tables for TD-assigned devices.
>>
>>    2) Trusted invalidation queue
>>       - A second invalidation-queue address register plus dedicated
>>         head/tail registers, also restricted to SEAM SAI.
>>
>>    3) IOTLB / DID isolation
>>       - When TDX Connect is enabled, VT-d restricts VMM DID usage and
>>         reserves the DID MSB namespace bit for TDX-module use.
>>
>> This posting focuses on VT-d-side enablement only: it enables those
>> extension-defined resources and control points while preserving existing
>> host VT-d behavior for non-trusted flows. Higher-layer integration
>> (TDX guest/device flows) will be posted separately.
>>
> 
> Jason had a comment on this from another thread [1]:
> 
> "
> Okay, so I saw the driver posting for basic iommu support, can we try
> to rework that to be split out like Aneesh is doing so everything
> about TDX calls lives in tsm and intel iommu only provides a small API
> surface to exchange whatever details are needed to bootstrap TDX
> module?
> "
> 
> [1] https://lore.kernel.org/all/20260916123954.GC3196566@ziepe.ca/

Yes, I will head in this direction in the next version.

Thanks,
baolu