Re: [PATCH v3 00/23] Add SMMUv3 Stage 1 Support for Xen guests

[Julien Grall <julien@xxxxxxx>]

Hi Milan,

On 31/03/2026 10:51, Milan Djokic wrote:
> This patch series provides emulated SMMUv3 support in Xen, enabling stage-1
> translation for the guest OS.
>
> Stage 1 translation support is required to provide isolation between different
> devices within OS. Xen already supports Stage 2 translation but there is no
> support for Stage 1 translation. The goal of this work is to support Stage 1
> translation for Xen guests.
>
> This patch series represents a continuation of work from Rahul Singh:
> https://patchwork.kernel.org/project/xen-devel/cover/cover.1669888522.git.rahul.singh@xxxxxxx/
> Original patch series is aligned with the newest Xen structure, with the 
> addition
> of translation layer which provides 1:N vIOMMU->pIOMMU mapping, in order to
> support passthrough of the devices attached to different physical IOMMUs.
>
> We cannot trust the guest OS to control the SMMUv3 hardware directly as
> compromised guest OS can corrupt the SMMUv3 configuration and make the system
> vulnerable. The guest gets the ownership of the stage 1 page tables and also
> owns stage 1 configuration structures. The Xen handles the root configuration
> structure (for security reasons), including the stage 2 configuration.
>
> XEN will emulate the SMMUv3 hardware and expose the virtual SMMUv3 to the
> guest. Guest can use the native SMMUv3 driver to configure the stage 1
> translation. When the guest configures the SMMUv3 for Stage 1, XEN will trap
> the access and configure hardware.
>
> SMMUv3 Driver(Guest OS) -> Configure the Stage-1 translation ->
> XEN trap access -> XEN SMMUv3 driver configure the HW.
>
> The final patch series commit provides a design document for the emulated
> IOMMU (arm-viommu.rst), which was previously discussed with the maintainers.
> Details regarding implementation, future work and security risks are outlined
> in this document.
>
> ---
> Changes in v2:
>   - Updated design and implementation with vIOMMU->pIOMMU mapping layer
>   - Addressed security risks in the design, provided initial performance
>     measurements
>   - Addressed comments from previous version
>   - Tested on Renesas R-Car platform, initial performance measurements for
>     stage-1 vs stage-1-less guests
> ---
>
> ---
> Changes in v3:
>   - Bump domctl version, added explicit padding for the new domctl structures
>   - Remove unnecessary changes according to review comments
>   - Add "ARM" prefix for vIOMMU Kconfig options, since only ARM architecture is
>     supported at this point
>   - Re-generate go code
>   - Add missing commit sign-off tags
Can you please avoid posting new revision in reply-to a previous one? 
This makes tracking quite difficult on the reviewer side. So I ended up 
starting to post comments on v2. Please have a look at them.
Cheers,

--
Julien Grall