Re: [PATCH v2 17/22] iommu/arm-smmu-v3-iommufd: Support implementation-defined hw_info

Pranjal Shrivastava
2025-04-29T21:44:12Z

On Fri, Apr 25, 2025 at 10:58:12PM -0700, Nicolin Chen wrote:
> Repurpose the @__reserved field in the struct iommu_hw_info_arm_smmuv3,
> to an HW implementation-defined field @impl.
>
> This will be used by Tegra241 CMDQV implementation on top of a standard
> ARM SMMUv3 IOMMU. The @impl will be only valid if @flags is set with an
> implementation-defined flag.
>
> Thus in the driver-level, add an hw_info impl op that will return such
> a flag to use the impl field.
>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

Reviewed-by: Pranjal Shrivastava <praan@google.com>

> ---
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 +
> include/uapi/linux/iommufd.h | 4 ++--
> .../iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 16 +++++++++++++---
> 3 files changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> index a5835af72417..bab7a9ce1283 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -726,6 +726,7 @@ struct arm_smmu_impl_ops {
> struct arm_smmu_domain *smmu_domain, struct iommufd_ctx *ictx,
> unsigned int viommu_type,
> const struct iommu_user_data *user_data);
> + u32 (*hw_info)(struct arm_smmu_device *smmu, u32 *impl);
> };
>
> /* An SMMUv3 instance */
> diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
> index 06a763fda47f..b2614f0f1547 100644
> --- a/include/uapi/linux/iommufd.h
> +++ b/include/uapi/linux/iommufd.h
> @@ -554,7 +554,7 @@ struct iommu_hw_info_vtd {
> * (IOMMU_HW_INFO_TYPE_ARM_SMMUV3)
> *
> * @flags: Must be set to 0
> - * @__reserved: Must be 0
> + * @impl: Must be 0
> * @idr: Implemented features for ARM SMMU Non-secure programming interface
> * @iidr: Information about the implementation and implementer of ARM SMMU,
> * and architecture version supported
> @@ -585,7 +585,7 @@ struct iommu_hw_info_vtd {
> */
> struct iommu_hw_info_arm_smmuv3 {
> __u32 flags;
> - __u32 __reserved;
> + __u32 impl;
> __u32 idr[6];
> __u32 iidr;
> __u32 aidr;
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
> index a8a78131702d..63861c60b615 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
> @@ -10,7 +10,9 @@
> void *arm_smmu_hw_info(struct device *dev, u32 *length, u32 *type)
> {
> struct arm_smmu_master *master = dev_iommu_priv_get(dev);
> + struct arm_smmu_device *smmu = master->smmu;
> struct iommu_hw_info_arm_smmuv3 *info;
> + u32 flags = 0, impl = 0;
> u32 __iomem *base_idr;
> unsigned int i;
>
> @@ -18,15 +20,23 @@ void *arm_smmu_hw_info(struct device *dev, u32 *length, u32 *type)
> if (!info)
> return ERR_PTR(-ENOMEM);
>
> - base_idr = master->smmu->base + ARM_SMMU_IDR0;
> + base_idr = smmu->base + ARM_SMMU_IDR0;
> for (i = 0; i <= 5; i++)
> info->idr[i] = readl_relaxed(base_idr + i);
> - info->iidr = readl_relaxed(master->smmu->base + ARM_SMMU_IIDR);
> - info->aidr = readl_relaxed(master->smmu->base + ARM_SMMU_AIDR);
> + info->iidr = readl_relaxed(smmu->base + ARM_SMMU_IIDR);
> + info->aidr = readl_relaxed(smmu->base + ARM_SMMU_AIDR);
>
> *length = sizeof(*info);
> *type = IOMMU_HW_INFO_TYPE_ARM_SMMUV3;
>
> + if (smmu->impl_ops && smmu->impl_ops->hw_info) {
> + flags = smmu->impl_ops->hw_info(smmu, &impl);
> + if (flags) {
> + info->impl = impl;
> + info->flags |= flags;
> + }
> + }
> +
> return info;
> }
>
> --
> 2.43.0
>