Re: [PATCH RESEND v9 02/13] iommu/ioasid: Add ioasid references

[Auger Eric <eric.auger@redhat.com>]

Hi Jean,

On 8/17/20 7:15 PM, Jean-Philippe Brucker wrote:
> Let IOASID users take references to existing ioasids with ioasid_get().
> ioasid_put() drops a reference and only frees the ioasid when its
> reference number is zero. It returns true if the ioasid was freed.
> For drivers that don't call ioasid_get(), ioasid_put() is the same as
> ioasid_free().
> 
> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric

> ---
>  include/linux/ioasid.h      | 10 ++++++++--
>  drivers/iommu/intel/iommu.c |  4 ++--
>  drivers/iommu/intel/svm.c   |  6 +++---
>  drivers/iommu/ioasid.c      | 38 +++++++++++++++++++++++++++++++++----
>  4 files changed, 47 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
> index 6f000d7a0ddc..e9dacd4b9f6b 100644
> --- a/include/linux/ioasid.h
> +++ b/include/linux/ioasid.h
> @@ -34,7 +34,8 @@ struct ioasid_allocator_ops {
>  #if IS_ENABLED(CONFIG_IOASID)
>  ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
>  		      void *private);
> -void ioasid_free(ioasid_t ioasid);
> +void ioasid_get(ioasid_t ioasid);
> +bool ioasid_put(ioasid_t ioasid);
>  void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
>  		  bool (*getter)(void *));
>  int ioasid_register_allocator(struct ioasid_allocator_ops *allocator);
> @@ -48,10 +49,15 @@ static inline ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min,
>  	return INVALID_IOASID;
>  }
>  
> -static inline void ioasid_free(ioasid_t ioasid)
> +static inline void ioasid_get(ioasid_t ioasid)
>  {
>  }
>  
> +static inline bool ioasid_put(ioasid_t ioasid)
> +{
> +	return false;
> +}
> +
>  static inline void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
>  				bool (*getter)(void *))
>  {
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index e9864e52b0e9..152fc2dc17e0 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -5149,7 +5149,7 @@ static void auxiliary_unlink_device(struct dmar_domain *domain,
>  	domain->auxd_refcnt--;
>  
>  	if (!domain->auxd_refcnt && domain->default_pasid > 0)
> -		ioasid_free(domain->default_pasid);
> +		ioasid_put(domain->default_pasid);
>  }
>  
>  static int aux_domain_add_dev(struct dmar_domain *domain,
> @@ -5210,7 +5210,7 @@ static int aux_domain_add_dev(struct dmar_domain *domain,
>  	spin_unlock(&iommu->lock);
>  	spin_unlock_irqrestore(&device_domain_lock, flags);
>  	if (!domain->auxd_refcnt && domain->default_pasid > 0)
> -		ioasid_free(domain->default_pasid);
> +		ioasid_put(domain->default_pasid);
>  
>  	return ret;
>  }
> diff --git a/drivers/iommu/intel/svm.c b/drivers/iommu/intel/svm.c
> index 95c3164a2302..50897a2bd1da 100644
> --- a/drivers/iommu/intel/svm.c
> +++ b/drivers/iommu/intel/svm.c
> @@ -565,7 +565,7 @@ intel_svm_bind_mm(struct device *dev, int flags, struct svm_dev_ops *ops,
>  		if (mm) {
>  			ret = mmu_notifier_register(&svm->notifier, mm);
>  			if (ret) {
> -				ioasid_free(svm->pasid);
> +				ioasid_put(svm->pasid);
>  				kfree(svm);
>  				kfree(sdev);
>  				goto out;
> @@ -583,7 +583,7 @@ intel_svm_bind_mm(struct device *dev, int flags, struct svm_dev_ops *ops,
>  		if (ret) {
>  			if (mm)
>  				mmu_notifier_unregister(&svm->notifier, mm);
> -			ioasid_free(svm->pasid);
> +			ioasid_put(svm->pasid);
>  			kfree(svm);
>  			kfree(sdev);
>  			goto out;
> @@ -652,7 +652,7 @@ static int intel_svm_unbind_mm(struct device *dev, int pasid)
>  			kfree_rcu(sdev, rcu);
>  
>  			if (list_empty(&svm->devs)) {
> -				ioasid_free(svm->pasid);
> +				ioasid_put(svm->pasid);
>  				if (svm->mm)
>  					mmu_notifier_unregister(&svm->notifier, svm->mm);
>  				list_del(&svm->list);
> diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
> index 0f8dd377aada..50ee27bbd04e 100644
> --- a/drivers/iommu/ioasid.c
> +++ b/drivers/iommu/ioasid.c
> @@ -2,7 +2,7 @@
>  /*
>   * I/O Address Space ID allocator. There is one global IOASID space, split into
>   * subsets. Users create a subset with DECLARE_IOASID_SET, then allocate and
> - * free IOASIDs with ioasid_alloc and ioasid_free.
> + * free IOASIDs with ioasid_alloc and ioasid_put.
>   */
>  #include <linux/ioasid.h>
>  #include <linux/module.h>
> @@ -15,6 +15,7 @@ struct ioasid_data {
>  	struct ioasid_set *set;
>  	void *private;
>  	struct rcu_head rcu;
> +	refcount_t refs;
>  };
>  
>  /*
> @@ -314,6 +315,7 @@ ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
>  
>  	data->set = set;
>  	data->private = private;
> +	refcount_set(&data->refs, 1);
>  
>  	/*
>  	 * Custom allocator needs allocator data to perform platform specific
> @@ -346,11 +348,34 @@ ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
>  EXPORT_SYMBOL_GPL(ioasid_alloc);
>  
>  /**
> - * ioasid_free - Free an IOASID
> + * ioasid_get - obtain a reference to the IOASID
> + */
> +void ioasid_get(ioasid_t ioasid)
> +{
> +	struct ioasid_data *ioasid_data;
> +
> +	spin_lock(&ioasid_allocator_lock);
> +	ioasid_data = xa_load(&active_allocator->xa, ioasid);
> +	if (ioasid_data)
> +		refcount_inc(&ioasid_data->refs);
> +	else
> +		WARN_ON(1);
> +	spin_unlock(&ioasid_allocator_lock);
> +}
> +EXPORT_SYMBOL_GPL(ioasid_get);
> +
> +/**
> + * ioasid_put - Release a reference to an ioasid
>   * @ioasid: the ID to remove
> + *
> + * Put a reference to the IOASID, free it when the number of references drops to
> + * zero.
> + *
> + * Return: %true if the IOASID was freed, %false otherwise.
>   */
> -void ioasid_free(ioasid_t ioasid)
> +bool ioasid_put(ioasid_t ioasid)
>  {
> +	bool free = false;
>  	struct ioasid_data *ioasid_data;
>  
>  	spin_lock(&ioasid_allocator_lock);
> @@ -360,6 +385,10 @@ void ioasid_free(ioasid_t ioasid)
>  		goto exit_unlock;
>  	}
>  
> +	free = refcount_dec_and_test(&ioasid_data->refs);
> +	if (!free)
> +		goto exit_unlock;
> +
>  	active_allocator->ops->free(ioasid, active_allocator->ops->pdata);
>  	/* Custom allocator needs additional steps to free the xa element */
>  	if (active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) {
> @@ -369,8 +398,9 @@ void ioasid_free(ioasid_t ioasid)
>  
>  exit_unlock:
>  	spin_unlock(&ioasid_allocator_lock);
> +	return free;
>  }
> -EXPORT_SYMBOL_GPL(ioasid_free);
> +EXPORT_SYMBOL_GPL(ioasid_put);
>  
>  /**
>   * ioasid_find - Find IOASID data
> 

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