Re: [PATCH v2 7/8] iommu/arm-smmu-v3: Implement IOMMU_HWPT_ALLOC_NEST_PARENT

[Mostafa Saleh <smostafa@google.com>]

Hi Jason,

On Tue, Aug 27, 2024 at 12:51:37PM -0300, Jason Gunthorpe wrote:
> For SMMUv3 the parent must be a S2 domain, which can be composed
> into a IOMMU_DOMAIN_NESTED.
> 
> In future the S2 parent will also need a VMID linked to the VIOMMU and
> even to KVM.
> 
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index ec2fcdd4523a26..8db3db6328f8b7 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -3103,7 +3103,8 @@ arm_smmu_domain_alloc_user(struct device *dev, u32 flags,
>  			   const struct iommu_user_data *user_data)
>  {
>  	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
> -	const u32 PAGING_FLAGS = IOMMU_HWPT_ALLOC_DIRTY_TRACKING;
> +	const u32 PAGING_FLAGS = IOMMU_HWPT_ALLOC_DIRTY_TRACKING |
> +				 IOMMU_HWPT_ALLOC_NEST_PARENT;
>  	struct arm_smmu_domain *smmu_domain;
>  	int ret;
>  
> @@ -3116,6 +3117,14 @@ arm_smmu_domain_alloc_user(struct device *dev, u32 flags,
>  	if (!smmu_domain)
>  		return ERR_PTR(-ENOMEM);
>  
> +	if (flags & IOMMU_HWPT_ALLOC_NEST_PARENT) {
> +		if (!(master->smmu->features & ARM_SMMU_FEAT_NESTING)) {
> +			ret = -EOPNOTSUPP;
I think that should be:
	ret = ERR_PTR(-EOPNOTSUPP);

Thanks,
Mostafa
> +			goto err_free;
> +		}
> +		smmu_domain->stage = ARM_SMMU_DOMAIN_S2;
> +	}
> +
>  	smmu_domain->domain.type = IOMMU_DOMAIN_UNMANAGED;
>  	smmu_domain->domain.ops = arm_smmu_ops.default_domain_ops;
>  	ret = arm_smmu_domain_finalise(smmu_domain, master->smmu, flags);
> -- 
> 2.46.0
>