Re: [PATCH v1 12/14] iommu/arm-smmu-v3: Support IOMMU_DOMAIN_NESTED type of allocations

[Eric Auger]

Hi Nicolin,

On 3/9/23 11:53, Nicolin Chen wrote:
> Add domain allocation support for IOMMU_DOMAIN_NESTED type. This includes
> the "finalise" part to log in the user space Stream Table Entry info.

Please explain the domain ops specialization.
>
> Co-developed-by: Eric Auger <eric.auger@xxxxxxxxxx>
> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
> Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 38 +++++++++++++++++++--
>  1 file changed, 36 insertions(+), 2 deletions(-)
>
> 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 5ff74edfbd68..1f318b5e0921 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2214,6 +2214,19 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain,
>  		return 0;
>  	}
>  
> +	if (domain->type == IOMMU_DOMAIN_NESTED) {
> +		if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S1) ||
> +		    !(smmu->features & ARM_SMMU_FEAT_TRANS_S2)) {
> +			dev_dbg(smmu->dev, "does not implement two stages\n");
> +			return -EINVAL;
> +		}
> +		smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
> +		smmu_domain->s1_cfg.s1fmt = user_cfg->s1fmt;
> +		smmu_domain->s1_cfg.s1cdmax = user_cfg->s1cdmax;
> +		smmu_domain->s1_cfg.cdcfg.cdtab_dma = user_cfg->s1ctxptr;
> +		return 0;
> +	}
> +
>  	if (user_cfg_s2 && !(smmu->features & ARM_SMMU_FEAT_TRANS_S2))
>  		return -EINVAL;
>  	if (user_cfg_s2)
> @@ -2863,6 +2876,11 @@ static void arm_smmu_remove_dev_pasid(struct device *dev, ioasid_t pasid)
>  	arm_smmu_sva_remove_dev_pasid(domain, dev, pasid);
>  }
>  
> +static const struct iommu_domain_ops arm_smmu_nested_domain_ops = {
> +	.attach_dev		= arm_smmu_attach_dev,
> +	.free			= arm_smmu_domain_free,
> +};
> +
>  static struct iommu_domain *
>  __arm_smmu_domain_alloc(unsigned type,
>  			struct arm_smmu_domain *s2,
> @@ -2877,11 +2895,15 @@ __arm_smmu_domain_alloc(unsigned type,
>  		return arm_smmu_sva_domain_alloc();
>  
>  	if (type != IOMMU_DOMAIN_UNMANAGED &&
> +	    type != IOMMU_DOMAIN_NESTED &&
>  	    type != IOMMU_DOMAIN_DMA &&
>  	    type != IOMMU_DOMAIN_DMA_FQ &&
>  	    type != IOMMU_DOMAIN_IDENTITY)
>  		return NULL;
>  
> +	if (s2 && s2->stage != ARM_SMMU_DOMAIN_S2)
> +		return NULL;
> +
>  	/*
>  	 * Allocate the domain and initialise some of its data structures.
>  	 * We can't really finalise the domain unless a master is given.
> @@ -2889,10 +2911,14 @@ __arm_smmu_domain_alloc(unsigned type,
>  	smmu_domain = kzalloc(sizeof(*smmu_domain), GFP_KERNEL);
>  	if (!smmu_domain)
>  		return NULL;
> +	smmu_domain->s2 = s2;
>  	domain = &smmu_domain->domain;
>  
>  	domain->type = type;
> -	domain->ops = arm_smmu_ops.default_domain_ops;
> +	if (s2)
> +		domain->ops = &arm_smmu_nested_domain_ops;
> +	else
> +		domain->ops = arm_smmu_ops.default_domain_ops;
>  
>  	mutex_init(&smmu_domain->init_mutex);
>  	INIT_LIST_HEAD(&smmu_domain->devices);
> @@ -2923,8 +2949,16 @@ arm_smmu_domain_alloc_user(struct device *dev, struct iommu_domain *parent,
>  	const struct iommu_hwpt_arm_smmuv3 *user_cfg = user_data;
>  	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
>  	unsigned type = IOMMU_DOMAIN_UNMANAGED;
> +	struct arm_smmu_domain *s2 = NULL;
> +
> +	if (parent) {
> +		if (parent->ops != arm_smmu_ops.default_domain_ops)
> +			return NULL;
> +		type = IOMMU_DOMAIN_NESTED;
> +		s2 = to_smmu_domain(parent);
> +	}
Please can you explain the (use) case where !parent. This creates an
unmanaged S1?

Thanks

Eric
>  
> -	return __arm_smmu_domain_alloc(type, NULL, master, user_cfg);
> +	return __arm_smmu_domain_alloc(type, s2, master, user_cfg);
>  }
>  
>  static struct iommu_ops arm_smmu_ops = {