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Date:   Thu, 31 Mar 2022 13:59:22 -0700
From:   Jacob Pan <jacob.jun.pan@intel.com>
To:     Lu Baolu <baolu.lu@linux.intel.com>
Cc:     Joerg Roedel <joro@8bytes.org>, Jason Gunthorpe <jgg@nvidia.com>,
        Christoph Hellwig <hch@infradead.org>,
        Kevin Tian <kevin.tian@intel.com>,
        Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        Eric Auger <eric.auger@redhat.com>,
        Liu Yi L <yi.l.liu@intel.com>,
        <iommu@lists.linux-foundation.org>, <linux-kernel@vger.kernel.org>,
        jacob.jun.pan@intel.com
Subject: Re: [PATCH RFC v2 08/11] iommu/sva: Use attach/detach_pasid_dev in
 SVA interfaces
Message-ID: <20220331135922.6c677117@jacob-builder>
In-Reply-To: <20220329053800.3049561-9-baolu.lu@linux.intel.com>
References: <20220329053800.3049561-1-baolu.lu@linux.intel.com>
        <20220329053800.3049561-9-baolu.lu@linux.intel.com>
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Hi Lu,

On Tue, 29 Mar 2022 13:37:57 +0800, Lu Baolu <baolu.lu@linux.intel.com>
wrote:

> The existing iommu SVA interfaces are implemented by calling the SVA
> specific iommu ops provided by the IOMMU drivers. There's no need for
> any SVA specific ops in iommu_ops vector anymore as we can achieve
> this through the generic attach/detach_dev_pasid domain ops.
> 
> This refactors the IOMMU SVA interfaces implementation by using the
> attach/detach_pasid_dev ops and align them with the concept of the
> iommu domain. Put the new SVA code in the sva related file in order
> to make it self-contained.
> 
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  include/linux/iommu.h         |  51 +++++++++-------
>  drivers/iommu/iommu-sva-lib.c | 110 +++++++++++++++++++++++++++++++++-
>  drivers/iommu/iommu.c         |  92 ----------------------------
>  3 files changed, 138 insertions(+), 115 deletions(-)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index a46285488a57..11c4d99e122d 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -629,7 +629,12 @@ struct iommu_fwspec {
>   * struct iommu_sva - handle to a device-mm bond
>   */
>  struct iommu_sva {
> -	struct device			*dev;
> +	struct device		*dev;
> +	ioasid_t		pasid;
> +	struct iommu_domain	*domain;
> +	/* Link to sva domain's bonds list */
> +	struct list_head	node;
> +	refcount_t		users;
>  };
>  
>  int iommu_fwspec_init(struct device *dev, struct fwnode_handle
> *iommu_fwnode, @@ -672,12 +677,6 @@ int iommu_dev_enable_feature(struct
> device *dev, enum iommu_dev_features f); int
> iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features f);
> bool iommu_dev_feature_enabled(struct device *dev, enum
> iommu_dev_features f); -struct iommu_sva *iommu_sva_bind_device(struct
> device *dev,
> -					struct mm_struct *mm,
> -					void *drvdata);
> -void iommu_sva_unbind_device(struct iommu_sva *handle);
> -u32 iommu_sva_get_pasid(struct iommu_sva *handle);
> -
>  int iommu_device_use_default_domain(struct device *dev);
>  void iommu_device_unuse_default_domain(struct device *dev);
>  
> @@ -1018,21 +1017,6 @@ iommu_dev_disable_feature(struct device *dev, enum
> iommu_dev_features feat) return -ENODEV;
>  }
>  
> -static inline struct iommu_sva *
> -iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void
> *drvdata) -{
> -	return NULL;
> -}
> -
> -static inline void iommu_sva_unbind_device(struct iommu_sva *handle)
> -{
> -}
> -
> -static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
> -{
> -	return IOMMU_PASID_INVALID;
> -}
> -
>  static inline struct iommu_fwspec *dev_iommu_fwspec_get(struct device
> *dev) {
>  	return NULL;
> @@ -1085,6 +1069,29 @@ iommu_put_domain_for_dev_pasid(struct iommu_domain
> *domain) }
>  #endif /* CONFIG_IOMMU_API */
>  
> +#ifdef CONFIG_IOMMU_SVA
> +struct iommu_sva *iommu_sva_bind_device(struct device *dev,
> +					struct mm_struct *mm,
> +					void *drvdata);
> +void iommu_sva_unbind_device(struct iommu_sva *handle);
> +u32 iommu_sva_get_pasid(struct iommu_sva *handle);
> +#else /* CONFIG_IOMMU_SVA */
> +static inline struct iommu_sva *
> +iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void
> *drvdata) +{
> +	return NULL;
> +}
> +
> +static inline void iommu_sva_unbind_device(struct iommu_sva *handle)
> +{
> +}
> +
> +static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
> +{
> +	return IOMMU_PASID_INVALID;
> +}
> +#endif /* CONFIG_IOMMU_SVA */
> +
>  /**
>   * iommu_map_sgtable - Map the given buffer to the IOMMU domain
>   * @domain:	The IOMMU domain to perform the mapping
> diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
> index 78820be23f15..1b45b7d01836 100644
> --- a/drivers/iommu/iommu-sva-lib.c
> +++ b/drivers/iommu/iommu-sva-lib.c
> @@ -17,6 +17,7 @@ struct iommu_sva_cookie {
>  	struct mm_struct *mm;
>  	ioasid_t pasid;
>  	refcount_t users;
> +	struct list_head bonds;
>  };
>  
>  /**
> @@ -101,6 +102,7 @@ iommu_sva_alloc_domain(struct device *dev, struct
> mm_struct *mm) cookie->mm = mm;
>  	cookie->pasid = mm->pasid;
>  	refcount_set(&cookie->users, 1);
> +	INIT_LIST_HEAD(&cookie->bonds);
>  	domain->type = IOMMU_DOMAIN_SVA;
>  	domain->sva_cookie = cookie;
>  	curr = xa_store(&sva_domain_array, mm->pasid, domain,
> GFP_KERNEL); @@ -118,6 +120,7 @@ iommu_sva_alloc_domain(struct device
> *dev, struct mm_struct *mm) static void iommu_sva_free_domain(struct
> iommu_domain *domain) {
>  	xa_erase(&sva_domain_array, domain->sva_cookie->pasid);
> +	WARN_ON(!list_empty(&domain->sva_cookie->bonds));
>  	kfree(domain->sva_cookie);
>  	domain->ops->free(domain);
>  }
> @@ -137,7 +140,7 @@ void iommu_sva_domain_put_user(struct iommu_domain
> *domain) iommu_sva_free_domain(domain);
>  }
>  
> -static __maybe_unused struct iommu_domain *
> +static struct iommu_domain *
>  iommu_sva_get_domain(struct device *dev, struct mm_struct *mm)
>  {
>  	struct iommu_domain *domain;
> @@ -158,3 +161,108 @@ struct mm_struct *iommu_sva_domain_mm(struct
> iommu_domain *domain) {
>  	return domain->sva_cookie->mm;
>  }
> +
> +/**
> + * iommu_sva_bind_device() - Bind a process address space to a device
> + * @dev: the device
> + * @mm: the mm to bind, caller must hold a reference to it
> + * @drvdata: opaque data pointer to pass to bind callback
> + *
> + * Create a bond between device and address space, allowing the device
> to access
> + * the mm using the returned PASID. If a bond already exists between
> @device and
> + * @mm, it is returned and an additional reference is taken. Caller must
> call
> + * iommu_sva_unbind_device() to release each reference.
> + *
> + * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called
> first, to
> + * initialize the required SVA features.
> + *
> + * On error, returns an ERR_PTR value.
> + */
> +struct iommu_sva *
> +iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void
> *drvdata) +{
> +	int ret = -EINVAL;
> +	struct iommu_sva *handle;
> +	struct iommu_domain *domain;
> +
> +	ret = iommu_sva_alloc_pasid(mm, 1, (1U <<
> dev->iommu->pasid_bits) - 1);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	mutex_lock(&iommu_sva_lock);
> +	domain = iommu_sva_get_domain(dev, mm);
> +	if (!domain) {
> +		ret = -ENOMEM;
> +		goto out_unlock;
> +	}
> +
> +	/* Search for an existing bond. */
> +	list_for_each_entry(handle, &domain->sva_cookie->bonds, node) {
> +		if (handle->dev == dev && handle->pasid == mm->pasid) {
> +			refcount_inc(&handle->users);
> +			mutex_lock(&iommu_sva_lock);
> +
> +			return handle;
> +		}
> +	}
> +
> +	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
> +	if (!handle) {
> +		ret = -ENOMEM;
> +		goto out_put_domain;
> +	}
> +
> +	ret = iommu_attach_device_pasid(domain, dev, mm->pasid);
> +	if (ret)
> +		goto out_free_handle;
> +
> +	handle->dev = dev;
> +	handle->domain = domain;
> +	handle->pasid = mm->pasid;
why do we need to store pasid here? Conceptually, pasid is per sva domain
not per bind. You can get it from handle->domain->sva_cookie.

> +	refcount_set(&handle->users, 1);
> +	list_add_tail(&handle->node, &domain->sva_cookie->bonds);
> +
> +	mutex_unlock(&iommu_sva_lock);
> +	return handle;
> +
> +out_free_handle:
> +	kfree(handle);
> +out_put_domain:
> +	iommu_sva_domain_put_user(domain);
> +out_unlock:
> +	mutex_unlock(&iommu_sva_lock);
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
> +
> +/**
> + * iommu_sva_unbind_device() - Remove a bond created with
> iommu_sva_bind_device
> + * @handle: the handle returned by iommu_sva_bind_device()
> + *
> + * Put reference to a bond between device and address space. The device
> should
> + * not be issuing any more transaction for this PASID. All outstanding
> page
> + * requests for this PASID must have been flushed to the IOMMU.
> + */
> +void iommu_sva_unbind_device(struct iommu_sva *handle)
> +{
> +	struct device *dev = handle->dev;
> +	struct iommu_domain *domain = handle->domain;
> +	struct mm_struct *mm = iommu_sva_domain_mm(domain);
> +
> +	mutex_lock(&iommu_sva_lock);
> +	if (refcount_dec_and_test(&handle->users)) {
> +		list_del(&handle->node);
> +		iommu_detach_device_pasid(domain, dev, mm->pasid);
> +		kfree(handle);
> +	}
> +
> +	iommu_sva_domain_put_user(domain);
> +	mutex_unlock(&iommu_sva_lock);
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_unbind_device);
> +
> +u32 iommu_sva_get_pasid(struct iommu_sva *handle)
> +{
> +	return handle->pasid;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 8163ad7f6902..6b51ead9d63b 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2712,98 +2712,6 @@ bool iommu_dev_feature_enabled(struct device *dev,
> enum iommu_dev_features feat) }
>  EXPORT_SYMBOL_GPL(iommu_dev_feature_enabled);
>  
> -/**
> - * iommu_sva_bind_device() - Bind a process address space to a device
> - * @dev: the device
> - * @mm: the mm to bind, caller must hold a reference to it
> - * @drvdata: opaque data pointer to pass to bind callback
> - *
> - * Create a bond between device and address space, allowing the device
> to access
> - * the mm using the returned PASID. If a bond already exists between
> @device and
> - * @mm, it is returned and an additional reference is taken. Caller must
> call
> - * iommu_sva_unbind_device() to release each reference.
> - *
> - * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called
> first, to
> - * initialize the required SVA features.
> - *
> - * On error, returns an ERR_PTR value.
> - */
> -struct iommu_sva *
> -iommu_sva_bind_device(struct device *dev, struct mm_struct *mm, void
> *drvdata) -{
> -	struct iommu_group *group;
> -	struct iommu_sva *handle = ERR_PTR(-EINVAL);
> -	const struct iommu_ops *ops = dev_iommu_ops(dev);
> -
> -	if (!ops->sva_bind)
> -		return ERR_PTR(-ENODEV);
> -
> -	group = iommu_group_get(dev);
> -	if (!group)
> -		return ERR_PTR(-ENODEV);
> -
> -	/* Ensure device count and domain don't change while we're
> binding */
> -	mutex_lock(&group->mutex);
> -
> -	/*
> -	 * To keep things simple, SVA currently doesn't support IOMMU
> groups
> -	 * with more than one device. Existing SVA-capable systems are
> not
> -	 * affected by the problems that required IOMMU groups (lack of
> ACS
> -	 * isolation, device ID aliasing and other hardware issues).
> -	 */
> -	if (!iommu_group_singleton_lockdown(group))
> -		goto out_unlock;
> -
> -	handle = ops->sva_bind(dev, mm, drvdata);
> -
> -out_unlock:
> -	mutex_unlock(&group->mutex);
> -	iommu_group_put(group);
> -
> -	return handle;
> -}
> -EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
> -
> -/**
> - * iommu_sva_unbind_device() - Remove a bond created with
> iommu_sva_bind_device
> - * @handle: the handle returned by iommu_sva_bind_device()
> - *
> - * Put reference to a bond between device and address space. The device
> should
> - * not be issuing any more transaction for this PASID. All outstanding
> page
> - * requests for this PASID must have been flushed to the IOMMU.
> - */
> -void iommu_sva_unbind_device(struct iommu_sva *handle)
> -{
> -	struct iommu_group *group;
> -	struct device *dev = handle->dev;
> -	const struct iommu_ops *ops = dev_iommu_ops(dev);
> -
> -	if (!ops->sva_unbind)
> -		return;
> -
> -	group = iommu_group_get(dev);
> -	if (!group)
> -		return;
> -
> -	mutex_lock(&group->mutex);
> -	ops->sva_unbind(handle);
> -	mutex_unlock(&group->mutex);
> -
> -	iommu_group_put(group);
> -}
> -EXPORT_SYMBOL_GPL(iommu_sva_unbind_device);
> -
> -u32 iommu_sva_get_pasid(struct iommu_sva *handle)
> -{
> -	const struct iommu_ops *ops = dev_iommu_ops(handle->dev);
> -
> -	if (!ops->sva_get_pasid)
> -		return IOMMU_PASID_INVALID;
> -
> -	return ops->sva_get_pasid(handle);
> -}
> -EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
> -
>  /*
>   * Changes the default domain of an iommu group that has *only* one
> device *


Thanks,

Jacob