Re: [PATCH v2 16/22] iommu/arm-smmu-v3-iommufd: Add vsmmu_alloc impl op

[Pranjal Shrivastava <praan@google.com>]

On Fri, Apr 25, 2025 at 10:58:11PM -0700, Nicolin Chen wrote:
> An impl driver might support its own vIOMMU object, as tegra241-cmdqv will
> add IOMMU_VIOMMU_TYPE_TEGRA241_CMDQV.
> 
> Add a vsmmu_alloc op to give impl a try, upon failure fallback to standard
> vsmmu allocation for IOMMU_VIOMMU_TYPE_ARM_SMMUV3.
> 
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

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

> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h     |  6 ++++++
>  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 17 +++++++++++------
>  2 files changed, 17 insertions(+), 6 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 6b8f0d20dac3..a5835af72417 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -16,6 +16,7 @@
>  #include <linux/sizes.h>
>  
>  struct arm_smmu_device;
> +struct arm_smmu_domain;
>  
>  /* MMIO registers */
>  #define ARM_SMMU_IDR0			0x0
> @@ -720,6 +721,11 @@ struct arm_smmu_impl_ops {
>  	int (*init_structures)(struct arm_smmu_device *smmu);
>  	struct arm_smmu_cmdq *(*get_secondary_cmdq)(
>  		struct arm_smmu_device *smmu, struct arm_smmu_cmdq_ent *ent);
> +	struct arm_vsmmu *(*vsmmu_alloc)(
> +		struct arm_smmu_device *smmu,
> +		struct arm_smmu_domain *smmu_domain, struct iommufd_ctx *ictx,
> +		unsigned int viommu_type,
> +		const struct iommu_user_data *user_data);
>  };
>  
>  /* An SMMUv3 instance */
> 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 66855cae775e..a8a78131702d 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
> @@ -392,10 +392,7 @@ struct iommufd_viommu *arm_vsmmu_alloc(struct device *dev,
>  		iommu_get_iommu_dev(dev, struct arm_smmu_device, iommu);
>  	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
>  	struct arm_smmu_domain *s2_parent = to_smmu_domain(parent);
> -	struct arm_vsmmu *vsmmu;
> -
> -	if (viommu_type != IOMMU_VIOMMU_TYPE_ARM_SMMUV3)
> -		return ERR_PTR(-EOPNOTSUPP);
> +	struct arm_vsmmu *vsmmu = ERR_PTR(-EOPNOTSUPP);
>  
>  	if (!(smmu->features & ARM_SMMU_FEAT_NESTING))
>  		return ERR_PTR(-EOPNOTSUPP);
> @@ -423,8 +420,16 @@ struct iommufd_viommu *arm_vsmmu_alloc(struct device *dev,
>  	    !(smmu->features & ARM_SMMU_FEAT_S2FWB))
>  		return ERR_PTR(-EOPNOTSUPP);
>  
> -	vsmmu = iommufd_viommu_alloc(ictx, struct arm_vsmmu, core,
> -				     &arm_vsmmu_ops);
> +	if (master->smmu->impl_ops && master->smmu->impl_ops->vsmmu_alloc)
> +		vsmmu = master->smmu->impl_ops->vsmmu_alloc(
> +			master->smmu, s2_parent, ictx, viommu_type, user_data);
> +	if (PTR_ERR(vsmmu) == -EOPNOTSUPP) {
> +		if (viommu_type != IOMMU_VIOMMU_TYPE_ARM_SMMUV3)
> +			return ERR_PTR(-EOPNOTSUPP);
> +		/* Fallback to standard SMMUv3 type if viommu_type matches */
> +		vsmmu = iommufd_viommu_alloc(ictx, struct arm_vsmmu, core,
> +					     &arm_vsmmu_ops);
> +	}
>  	if (IS_ERR(vsmmu))
>  		return ERR_CAST(vsmmu);
>  
> -- 
> 2.43.0
>