Re: [PATCH 2/2] iommufd: Report ATS not supported status via IOMMU_GET_HW_INFO

[Samiullah Khawaja]

On Tue, Mar 03, 2026 at 03:03:48PM +0000, Shameer Kolothum wrote:
> If the IOMMU driver reports that ATS is not supported for a device, set
> the IOMMU_HW_CAP_PCI_ATS_NOT_SUPPORTED flag in the returned hardware
> capabilities.
>
> When this flag is set, ATS is not supported and not used for the device.
>
> Signed-off-by: Shameer Kolothum <skolothumtho@xxxxxxxxxx>
> ---
> include/uapi/linux/iommufd.h   | 3 +++
> drivers/iommu/iommufd/device.c | 3 +++
> 2 files changed, 6 insertions(+)
>
> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> index 1dafbc552d37..d85a2d3e1b40 100644
> --- a/include/uapi/linux/iommufd.h
> +++ b/include/uapi/linux/iommufd.h
> @@ -695,11 +695,14 @@ enum iommu_hw_info_type {
>  * @IOMMU_HW_CAP_PCI_PASID_PRIV: Privileged Mode Supported, user ignores it
>  *                               when the struct
>  *                               iommu_hw_info::out_max_pasid_log2 is zero.
> + * @IOMMU_HW_CAP_PCI_ATS_NOT_SUPPORTED: ATS is not supported and not used on
> + *                                      this device.
>  */
> enum iommufd_hw_capabilities {
> 	IOMMU_HW_CAP_DIRTY_TRACKING = 1 << 0,
> 	IOMMU_HW_CAP_PCI_PASID_EXEC = 1 << 1,
> 	IOMMU_HW_CAP_PCI_PASID_PRIV = 1 << 2,
> +	IOMMU_HW_CAP_PCI_ATS_NOT_SUPPORTED = 1 << 3,
> };
>
> /**
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index 344d620cdecc..2e98818806c0 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -1624,6 +1624,9 @@ int iommufd_get_hw_info(struct iommufd_ucmd *ucmd)
> 	if (device_iommu_capable(idev->dev, IOMMU_CAP_DIRTY_TRACKING))
> 		cmd->out_capabilities |= IOMMU_HW_CAP_DIRTY_TRACKING;
>
> +	if (device_iommu_capable(idev->dev, IOMMU_CAP_PCI_ATS_NOT_SUPPORTED))
> +		cmd->out_capabilities |= IOMMU_HW_CAP_PCI_ATS_NOT_SUPPORTED;
> +
> 	cmd->out_max_pasid_log2 = 0;
> 	/*
> 	 * Currently, all iommu drivers enable PASID in the probe_device()
> --
> 2.43.0

Reviewed-by: Samiullah Khawaja <skhawaja@xxxxxxxxxx>