Re: [PATCH v5 11/17] iommu/arm-smmu-v3: Remove arm_smmu_master->domain

[Mostafa Saleh <smostafa@google.com>]

Hi Jason,

On Tue, Feb 06, 2024 at 11:12:48AM -0400, Jason Gunthorpe wrote:
> Introducing global statics which are of type struct iommu_domain, not
> struct arm_smmu_domain makes it difficult to retain
> arm_smmu_master->domain, as it can no longer point to an IDENTITY or
> BLOCKED domain.
> 
> The only place that uses the value is arm_smmu_detach_dev(). Change things
> to work like other drivers and call iommu_get_domain_for_dev() to obtain
> the current domain.
> 
> The master->domain is subtly protecting the domain_head against being
> unused, change the domain_head to be INIT'd when the master is not
> attached to a domain instead of garbage/zero.

I don't this the problem here, neither the reason for initialising the
domain_head, can you please clarify the issue?

> Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Tested-by: Nicolin Chen <nicolinc@nvidia.com>
> Tested-by: Moritz Fischer <moritzf@google.com>
> Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 26 ++++++++-------------
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  1 -
>  2 files changed, 10 insertions(+), 17 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 133f13f33df124..a98707cd1efccb 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2560,19 +2560,20 @@ static void arm_smmu_disable_pasid(struct arm_smmu_master *master)
>  
>  static void arm_smmu_detach_dev(struct arm_smmu_master *master)
>  {
> +	struct iommu_domain *domain = iommu_get_domain_for_dev(master->dev);
> +	struct arm_smmu_domain *smmu_domain;
>  	unsigned long flags;
> -	struct arm_smmu_domain *smmu_domain = master->domain;
>  
> -	if (!smmu_domain)
> +	if (!domain)
>  		return;
>  
> +	smmu_domain = to_smmu_domain(domain);
>  	arm_smmu_disable_ats(master, smmu_domain);
>  
>  	spin_lock_irqsave(&smmu_domain->devices_lock, flags);
> -	list_del(&master->domain_head);
> +	list_del_init(&master->domain_head);
>  	spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
>  
> -	master->domain = NULL;
>  	master->ats_enabled = false;
>  }
>  
> @@ -2626,8 +2627,6 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>  
>  	arm_smmu_detach_dev(master);
>  
> -	master->domain = smmu_domain;
> -
>  	/*
>  	 * The SMMU does not support enabling ATS with bypass. When the STE is
>  	 * in bypass (STE.Config[2:0] == 0b100), ATS Translation Requests and
> @@ -2646,10 +2645,8 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>  	case ARM_SMMU_DOMAIN_S1:
>  		if (!master->cd_table.cdtab) {
>  			ret = arm_smmu_alloc_cd_tables(master);
> -			if (ret) {
> -				master->domain = NULL;
> +			if (ret)
>  				goto out_list_del;
> -			}
>  		} else {
>  			/*
>  			 * arm_smmu_write_ctx_desc() relies on the entry being
> @@ -2657,17 +2654,13 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>  			 */
>  			ret = arm_smmu_write_ctx_desc(master, IOMMU_NO_PASID,
>  						      NULL);
> -			if (ret) {
> -				master->domain = NULL;
> +			if (ret)
>  				goto out_list_del;
> -			}
>  		}
>  
>  		ret = arm_smmu_write_ctx_desc(master, IOMMU_NO_PASID, &smmu_domain->cd);
> -		if (ret) {
> -			master->domain = NULL;
> +		if (ret)
>  			goto out_list_del;
> -		}
>  
>  		arm_smmu_make_cdtable_ste(&target, master);
>  		arm_smmu_install_ste_for_dev(master, &target);
> @@ -2693,7 +2686,7 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>  
>  out_list_del:
>  	spin_lock_irqsave(&smmu_domain->devices_lock, flags);
> -	list_del(&master->domain_head);
> +	list_del_init(&master->domain_head);
>  	spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
>  
>  out_unlock:
> @@ -2894,6 +2887,7 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
>  	master->dev = dev;
>  	master->smmu = smmu;
>  	INIT_LIST_HEAD(&master->bonds);
> +	INIT_LIST_HEAD(&master->domain_head);
>  	dev_iommu_priv_set(dev, master);
>  
>  	ret = arm_smmu_insert_master(smmu, master);
> 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 cbf4b57719b7b9..587f99701ad30f 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -696,7 +696,6 @@ struct arm_smmu_stream {
>  struct arm_smmu_master {
>  	struct arm_smmu_device		*smmu;
>  	struct device			*dev;
> -	struct arm_smmu_domain		*domain;
>  	struct list_head		domain_head;
>  	struct arm_smmu_stream		*streams;
>  	/* Locked by the iommu core using the group mutex */
> -- 
> 2.43.0
>
Thanks,
Mostafa