RE: [PATCH 09/10] iommu/ioasid: Support ioasid_set quota adjustment

[Tian, Kevin]

> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Sent: Thursday, March 26, 2020 1:56 AM
> 
> IOASID set is allocated with an initial quota, at runtime there may be
> needs to balance IOASID resources among different VMs/sets.
> 

I may overlook previous patches but I didn't see any place setting the
initial quota...

> This patch adds a new API to adjust per set quota.

since this is purely an internal kernel API, implies that the publisher
(e.g. VFIO) is responsible for exposing its own uAPI to set the quota?

> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> ---
>  drivers/iommu/ioasid.c | 44
> ++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/ioasid.h |  6 ++++++
>  2 files changed, 50 insertions(+)
> 
> diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
> index 27dce2cb5af2..5ac28862a1db 100644
> --- a/drivers/iommu/ioasid.c
> +++ b/drivers/iommu/ioasid.c
> @@ -578,6 +578,50 @@ void ioasid_free_set(int sid, bool destroy_set)
>  }
>  EXPORT_SYMBOL_GPL(ioasid_free_set);
> 
> +/**
> + * ioasid_adjust_set - Adjust the quota of an IOASID set
> + * @quota:	Quota allowed in this set
> + * @sid:	IOASID set ID to be assigned
> + *
> + * Return 0 on success. If the new quota is smaller than the number of
> + * IOASIDs already allocated, -EINVAL will be returned. No change will be
> + * made to the existing quota.
> + */
> +int ioasid_adjust_set(int sid, int quota)
> +{
> +	struct ioasid_set_data *sdata;
> +	int ret = 0;
> +
> +	mutex_lock(&ioasid_allocator_lock);
> +	sdata = xa_load(&ioasid_sets, sid);
> +	if (!sdata || sdata->nr_ioasids > quota) {
> +		pr_err("Failed to adjust IOASID set %d quota %d\n",
> +			sid, quota);
> +		ret = -EINVAL;
> +		goto done_unlock;
> +	}
> +
> +	if (quota >= ioasid_capacity_avail) {
> +		ret = -ENOSPC;
> +		goto done_unlock;
> +	}
> +
> +	/* Return the delta back to system pool */
> +	ioasid_capacity_avail += sdata->size - quota;
> +
> +	/*
> +	 * May have a policy to prevent giving all available IOASIDs
> +	 * to one set. But we don't enforce here, it should be in the
> +	 * upper layers.
> +	 */
> +	sdata->size = quota;
> +
> +done_unlock:
> +	mutex_unlock(&ioasid_allocator_lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(ioasid_adjust_set);
> 
>  /**
>   * ioasid_find - Find IOASID data
> diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
> index 32d032913828..6e7de6fb91bf 100644
> --- a/include/linux/ioasid.h
> +++ b/include/linux/ioasid.h
> @@ -73,6 +73,7 @@ int ioasid_alloc_set(struct ioasid_set *token, ioasid_t
> quota, int *sid);
>  void ioasid_free_set(int sid, bool destroy_set);
>  int ioasid_find_sid(ioasid_t ioasid);
>  int ioasid_notify(ioasid_t id, enum ioasid_notify_val cmd);
> +int ioasid_adjust_set(int sid, int quota);
> 
>  #else /* !CONFIG_IOASID */
>  static inline ioasid_t ioasid_alloc(int sid, ioasid_t min,
> @@ -136,5 +137,10 @@ static inline int ioasid_alloc_system_set(int quota)
>  	return -ENOTSUPP;
>  }
> 
> +static inline int ioasid_adjust_set(int sid, int quota)
> +{
> +	return -ENOTSUPP;
> +}
> +
>  #endif /* CONFIG_IOASID */
>  #endif /* __LINUX_IOASID_H */
> --
> 2.7.4