[v3,06/10] iommu/sva: Search mm by PASID

The fault handler will need to find an mm given its PASID. This is the
reason we have an IDR for storing address spaces, so hook it up.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
---
 drivers/iommu/iommu-sva.c | 26 ++++++++++++++++++++++++++
 include/linux/iommu.h     |  7 +++++++
 2 files changed, 33 insertions(+)

Hi,

On 09/21/2018 01:00 AM, Jean-Philippe Brucker wrote:
> The fault handler will need to find an mm given its PASID. This is the
> reason we have an IDR for storing address spaces, so hook it up.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
> ---
>   drivers/iommu/iommu-sva.c | 26 ++++++++++++++++++++++++++
>   include/linux/iommu.h     |  7 +++++++
>   2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
> index 5ff8967cb213..ee86f00ee1b9 100644
> --- a/drivers/iommu/iommu-sva.c
> +++ b/drivers/iommu/iommu-sva.c
> @@ -636,6 +636,32 @@ void iommu_sva_unbind_device_all(struct device *dev)
>   }
>   EXPORT_SYMBOL_GPL(iommu_sva_unbind_device_all);
>   
> +/**
> + * iommu_sva_find() - Find mm associated to the given PASID
> + * @pasid: Process Address Space ID assigned to the mm
> + *
> + * Returns the mm corresponding to this PASID, or NULL if not found. A reference
> + * to the mm is taken, and must be released with mmput().
> + */
> +struct mm_struct *iommu_sva_find(int pasid)
> +{
> +	struct io_mm *io_mm;
> +	struct mm_struct *mm = NULL;
> +
> +	spin_lock(&iommu_sva_lock);
> +	io_mm = idr_find(&iommu_pasid_idr, pasid);

The same thing here. We can't guarantee that a pointer of mm_struct type
is associated with a pasid value when pasid is also used for other
purposes. If hardware reports a bad pasid, this function might run into
problem.

Best regards,
Lu Baolu

> +	if (io_mm && io_mm_get_locked(io_mm)) {
> +		if (mmget_not_zero(io_mm->mm))
> +			mm = io_mm->mm;
> +
> +		io_mm_put_locked(io_mm);
> +	}
> +	spin_unlock(&iommu_sva_lock);
> +
> +	return mm;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_find);
> +
>   /**
>    * iommu_sva_init_device() - Initialize Shared Virtual Addressing for a device
>    * @dev: the device
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 429f3dc37a35..a457650b80de 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -987,6 +987,8 @@ extern int __iommu_sva_bind_device(struct device *dev, struct mm_struct *mm,
>   				   void *drvdata);
>   extern int __iommu_sva_unbind_device(struct device *dev, int pasid);
>   extern void iommu_sva_unbind_device_all(struct device *dev);
> +extern struct mm_struct *iommu_sva_find(int pasid);
> +
>   #else /* CONFIG_IOMMU_SVA */
>   static inline int iommu_sva_init_device(struct device *dev,
>   					unsigned long features,
> @@ -1016,6 +1018,11 @@ static inline int __iommu_sva_unbind_device(struct device *dev, int pasid)
>   static inline void iommu_sva_unbind_device_all(struct device *dev)
>   {
>   }
> +
> +static inline struct mm_struct *iommu_sva_find(int pasid)
> +{
> +	return NULL;
> +}
>   #endif /* CONFIG_IOMMU_SVA */
>   
>   #endif /* __LINUX_IOMMU_H */
>