Re: [PATCH 2/2] iommu/tegra241-cmdqv: Update uAPI to clarify HYP_OWN requirement

[Will Deacon]

On Thu, Mar 12, 2026 at 05:36:35PM -0700, Nicolin Chen wrote:
> From hardware implementation perspective, a guest tegra241-cmdqv hardware
> is different than the host hardware:
>  - Host HW is backed by a VINTF (HYP_OWN=1)
>  - Guest HW is backed by a VINTF (HYP_OWN=0)
> 
> The kernel driver has an implementation requirement of the HYP_OWN bit in
> the VM. So, VMM must follow that to allow the same copy of Linux to work.
> 
> Add this requirement to the uAPI, which is currently missing.
> 
> Fixes: 4dc0d12474f9 ("iommu/tegra241-cmdqv: Add user-space use support")
> Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> ---
>  include/uapi/linux/iommufd.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> index 1dafbc552d37d..f63edbe71d542 100644
> --- a/include/uapi/linux/iommufd.h
> +++ b/include/uapi/linux/iommufd.h
> @@ -1052,6 +1052,11 @@ struct iommu_fault_alloc {
>  enum iommu_viommu_type {
>  	IOMMU_VIOMMU_TYPE_DEFAULT = 0,
>  	IOMMU_VIOMMU_TYPE_ARM_SMMUV3 = 1,
> +	/*
> +	 * TEGRA241_CMDQV requirements (otherwise, VCMDQs will not work)
> +	 * - Kernel will allocate a VINTF (HYP_OWN=0) to back this VIOMMU. So,
> +	 *   VMM must wire the HYP_OWN bit to 0 in guest VINTF_CONFIG register
> +	 */
>  	IOMMU_VIOMMU_TYPE_TEGRA241_CMDQV = 2,
>  };

Jason, are you happy with this one?

Will