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

[Robin Murphy]

On 2023-03-09 10:53, 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.
>
> 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;

How's that going to work? If the caller's asked for something we can't 
provide, returning something else and hoping it fails later is not 
sensible, we should just fail right here. It's even more worrying if 
there's a chance it *won't* fail later, and a guest ends up with 
"nested" translation giving it full access to host PA space :/

Thanks,
Robin.

> +	}
> +
>   	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);
> +	}
>   
> -	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 = {