linux-kernel - Re: [PATCH v10 07/12] arm-smmu-v3/sva: Add SVA domain support

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Date:   Sat, 23 Jul 2022 11:20:09 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Zhangfei Gao <zhangfei.gao@...aro.org>,
        Zhu Tony <tony.zhu@...el.com>, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [PATCH v10 07/12] arm-smmu-v3/sva: Add SVA domain support

On Tue, Jul 05, 2022 at 01:07:05PM +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@...ux.intel.com>
> Reviewed-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
> Tested-by: Zhangfei Gao <zhangfei.gao@...aro.org>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  6 ++
>  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c   | 69 +++++++++++++++++++
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   |  3 +
>  3 files changed, 78 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 d2ba86470c42..96399dd3a67a 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -758,6 +758,7 @@ 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);
> +struct iommu_domain *arm_smmu_sva_domain_alloc(void);
>  #else /* CONFIG_ARM_SMMU_V3_SVA */
>  static inline bool arm_smmu_sva_supported(struct arm_smmu_device *smmu)
>  {
> @@ -803,5 +804,10 @@ static inline u32 arm_smmu_sva_get_pasid(struct iommu_sva *handle)
>  }
>  
>  static inline void arm_smmu_sva_notifier_synchronize(void) {}
> +
> +static inline struct iommu_domain *arm_smmu_sva_domain_alloc(void)
> +{
> +	return NULL;
> +}
>  #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 f155d406c5d5..fc4555dac5b4 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
> @@ -549,3 +549,72 @@ void arm_smmu_sva_notifier_synchronize(void)
>  	 */
>  	mmu_notifier_synchronize();
>  }
> +
> +static int arm_smmu_sva_set_dev_pasid(struct iommu_domain *domain,
> +				      struct device *dev, ioasid_t id)
> +{
> +	int ret = 0;
> +	struct mm_struct *mm;
> +	struct iommu_sva *handle;
> +
> +	if (domain->type != IOMMU_DOMAIN_SVA)
> +		return -EINVAL;

Not needed, this function is only called from the sva ops, other
domain types are impossible, we don't need sanity tests in drivers

> +	mm = domain->mm;
> +	if (WARN_ON(!mm))
> +		return -ENODEV;

Also guarenteed by core code, don't need sanity tests

> +static void arm_smmu_sva_block_dev_pasid(struct iommu_domain *domain,
> +					 struct device *dev, ioasid_t id)
> +{
> +	struct mm_struct *mm = domain->mm;
> +	struct arm_smmu_bond *bond = NULL, *t;
> +	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;

This doesn't seem like what I would expect, the domain should be used
at the key in these datastructures, not the mm..

> index ae8ec8df47c1..a30b252e2f95 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -1999,6 +1999,9 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
>  {
>  	struct arm_smmu_domain *smmu_domain;
>  
> +	if (type == IOMMU_DOMAIN_SVA)
> +		return arm_smmu_sva_domain_alloc();

If no drivers are sharing any code with their other alloc paths perhaps we
should have a dedicated op for SVA?

Jason