Re: [RFC 00/11] hw/arm/smmuv3: Add initial support for Secure State

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

On 8/11/25 3:26 AM, Philippe Mathieu-Daudé wrote:
> On 10/8/25 18:11, Tao Tang wrote:
>>
>> On 2025/8/7 05:28, Pierrick Bouvier wrote:
>>> On 8/6/25 8:11 AM, Tao Tang wrote:
> 
> 
>>>> Secure Translation Path: Since the TF-A SMMUv3 Test Engine does not
>>>> support QEMU, and no secure device assignment feature exists yet, I
>>>> created a custom platform device to test the secure translation flow.
>>>> To trigger the translation logic, I initiated MMIO writes to this
>>>> device from within Hafnium. The device's MMIO callback handler then
>>>> performed DMA accesses via its IOMMU region, exercising the secure
>>>> translation path. While SMMUv3 is typically used for PCIe on
>>>> physical SoCs, the architecture allows its use with platform devices
>>>> via a stream-id binding in the device tree. The test harness
>>>> required some non-standard modifications to decouple the SMMU from
>>>> its tight integration with PCIe. The code for this test device is
>>>> available for review at [3]. README.md with detailed instructions is
>>>> also provided.
>>>>
>>>
>>> I am not sure about the current policy in QEMU for test oriented
>>> devices, but it would be really useful to have something similar
>>> upstream (Note: it's out of the scope of this series).
>>> One challenge working with SMMU emulation is that reproducing setups
>>> and triggering specific code paths is hard to achieve, due to the
>>> indirect use of SMMU feature (through DMA) and the complex software
>>> stack usually involved.
>>> Having something upstream available to work on SMMU emulation, at
>>> least on device side, would be a great addition.
>>>
>>> Eric, Peter, is this something that would be acceptable to merge?
> 
> 
> This shouldn't be an issue, we already have some:
> 
> $ git ls-files|fgrep testdev
> chardev/testdev.c
> docs/specs/pci-testdev.rst
> hw/hyperv/hyperv_testdev.c
> hw/misc/pc-testdev.c
> hw/misc/pci-testdev.c
> hw/tricore/tricore_testdevice.c
> 

Looks good indeed, and we have the TEST_DEVICES category for that.

> 
>> Looking ahead, my plan is to refactor the smmuv3-test platform device.
>> The goal is to make it self-contained within QEMU, removing the current
>> dependency on Hafnium to trigger its operations. I plan to submit this
>> as a separate RFC patch series in the next few days.
>