Re: [PATCH v5 07/12] arm-smmu-v3/sva: Add SVA domain support

[Jean-Philippe Brucker]

On Mon, May 02, 2022 at 09:48:37AM +0800, Lu Baolu wrote:
> Add support for SVA domain allocation and provide an SVA-specific
> iommu_domain_ops.
> 
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   | 14 +++++++
>  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c   | 42 +++++++++++++++++++
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 21 ++++++++++
>  3 files changed, 77 insertions(+)
> 
> 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 cd48590ada30..7631c00fdcbd 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -759,6 +759,10 @@ struct iommu_sva *arm_smmu_sva_bind(struct device *dev, struct mm_struct *mm,
>  void arm_smmu_sva_unbind(struct iommu_sva *handle);
>  u32 arm_smmu_sva_get_pasid(struct iommu_sva *handle);
>  void arm_smmu_sva_notifier_synchronize(void);
> +int arm_smmu_sva_attach_dev_pasid(struct iommu_domain *domain,
> +				  struct device *dev, ioasid_t id);
> +void arm_smmu_sva_detach_dev_pasid(struct iommu_domain *domain,
> +				   struct device *dev, ioasid_t id);
>  #else /* CONFIG_ARM_SMMU_V3_SVA */
>  static inline bool arm_smmu_sva_supported(struct arm_smmu_device *smmu)
>  {
> @@ -804,5 +808,15 @@ static inline u32 arm_smmu_sva_get_pasid(struct iommu_sva *handle)
>  }
>  
>  static inline void arm_smmu_sva_notifier_synchronize(void) {}
> +
> +static inline int arm_smmu_sva_attach_dev_pasid(struct iommu_domain *domain,
> +						struct device *dev, ioasid_t id)
> +{
> +	return -ENODEV;
> +}
> +
> +static inline void arm_smmu_sva_detach_dev_pasid(struct iommu_domain *domain,
> +						 struct device *dev,
> +						 ioasid_t id) {}
>  #endif /* CONFIG_ARM_SMMU_V3_SVA */
>  #endif /* _ARM_SMMU_V3_H */
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
> index c623dae1e115..3b843cd3ed67 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
> @@ -541,3 +541,45 @@ void arm_smmu_sva_notifier_synchronize(void)
>  	 */
>  	mmu_notifier_synchronize();
>  }
> +
> +int arm_smmu_sva_attach_dev_pasid(struct iommu_domain *domain,
> +				  struct device *dev, ioasid_t id)
> +{
> +	int ret = 0;
> +	struct iommu_sva *handle;
> +	struct mm_struct *mm = iommu_sva_domain_mm(domain);
> +
> +	if (domain->type != IOMMU_DOMAIN_SVA || !mm)

We wouldn't get that far with a non-SVA domain since iommu_sva_domain_mm()
would dereference a NULL pointer. Could you move it after the domain->type
check, and maybe add a WARN_ON()?  It could help catch issues in future
API changes.

> +		return -EINVAL;
> +
> +	mutex_lock(&sva_lock);
> +	handle = __arm_smmu_sva_bind(dev, mm);
> +	if (IS_ERR(handle))
> +		ret = PTR_ERR(handle);
> +	mutex_unlock(&sva_lock);
> +
> +	return ret;
> +}
> +
> +void arm_smmu_sva_detach_dev_pasid(struct iommu_domain *domain,
> +				   struct device *dev, ioasid_t id)
> +{
> +	struct arm_smmu_bond *bond = NULL, *t;
> +	struct mm_struct *mm = iommu_sva_domain_mm(domain);
> +	struct arm_smmu_master *master = dev_iommu_priv_get(dev);
> +
> +	mutex_lock(&sva_lock);
> +	list_for_each_entry(t, &master->bonds, list) {
> +		if (t->mm == mm) {
> +			bond = t;
> +			break;
> +		}
> +	}
> +
> +	if (!WARN_ON(!bond) && refcount_dec_and_test(&bond->refs)) {
> +		list_del(&bond->list);
> +		arm_smmu_mmu_notifier_put(bond->smmu_mn);
> +		kfree(bond);
> +	}
> +	mutex_unlock(&sva_lock);
> +}
> 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 afc63fce6107..bd80de0bad98 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -1995,10 +1995,31 @@ static bool arm_smmu_capable(enum iommu_cap cap)
>  	}
>  }
>  
> +static void arm_smmu_sva_domain_free(struct iommu_domain *domain)
> +{
> +	kfree(domain);
> +}
> +
> +static const struct iommu_domain_ops arm_smmu_sva_domain_ops = {
> +	.attach_dev_pasid	= arm_smmu_sva_attach_dev_pasid,
> +	.detach_dev_pasid	= arm_smmu_sva_detach_dev_pasid,
> +	.free			= arm_smmu_sva_domain_free,
> +};
> +
>  static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
>  {
>  	struct arm_smmu_domain *smmu_domain;
>  
> +	if (type == IOMMU_DOMAIN_SVA) {
> +		struct iommu_domain *domain;
> +
> +		domain = kzalloc(sizeof(*domain), GFP_KERNEL);
> +		if (domain)
> +			domain->ops = &arm_smmu_sva_domain_ops;
> +
> +		return domain;
> +	}
> +

I'd prefer moving all of this to arm-smmu-v3-sva.c and just call
arm_smmu_sva_domain_alloc() here

Otherwise the patch looks fine. I'll rework the driver when I find some
time, because we can now remove arm_smmu_bond and move smmu_mn to the SVA
domain, maybe also remove sva_lock but I haven't thought it through.

Thanks,
Jean

>  	if (type != IOMMU_DOMAIN_UNMANAGED &&
>  	    type != IOMMU_DOMAIN_DMA &&
>  	    type != IOMMU_DOMAIN_DMA_FQ &&
> -- 
> 2.25.1
>