RE: [PATCH 01/10] iommu/ioasid: Introduce system-wide capacity

[Tian, Kevin]

> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Sent: Thursday, March 26, 2020 1:55 AM
> 
> IOASID is a limited system-wide resource that can be allocated at
> runtime. This limitation can be enumerated during boot. For example, on
> x86 platforms, PCI Process Address Space ID (PASID) allocation uses
> IOASID service. The number of supported PASID bits are enumerated by
> extended capability register as defined in the VT-d spec.
> 
> This patch adds a helper to set the system capacity, it expected to be
> set during boot prior to any allocation request.
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> ---
>  drivers/iommu/ioasid.c | 15 +++++++++++++++
>  include/linux/ioasid.h |  5 ++++-
>  2 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
> index 0f8dd377aada..4026e52855b9 100644
> --- a/drivers/iommu/ioasid.c
> +++ b/drivers/iommu/ioasid.c
> @@ -17,6 +17,21 @@ struct ioasid_data {
>  	struct rcu_head rcu;
>  };
> 
> +static ioasid_t ioasid_capacity;
> +static ioasid_t ioasid_capacity_avail;
> +
> +/* System capacity can only be set once */
> +void ioasid_install_capacity(ioasid_t total)
> +{
> +	if (ioasid_capacity) {
> +		pr_warn("IOASID capacity already set at %d\n",
> ioasid_capacity);
> +		return;
> +	}
> +
> +	ioasid_capacity = ioasid_capacity_avail = total;
> +}
> +EXPORT_SYMBOL_GPL(ioasid_install_capacity);
> +

>From all the texts in this patch, looks ioasid_set_capacity might be
a better name?

>  /*
>   * struct ioasid_allocator_data - Internal data structure to hold information
>   * about an allocator. There are two types of allocators:
> diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
> index 6f000d7a0ddc..9711fa0dc357 100644
> --- a/include/linux/ioasid.h
> +++ b/include/linux/ioasid.h
> @@ -40,7 +40,7 @@ void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
>  int ioasid_register_allocator(struct ioasid_allocator_ops *allocator);
>  void ioasid_unregister_allocator(struct ioasid_allocator_ops *allocator);
>  int ioasid_set_data(ioasid_t ioasid, void *data);
> -
> +void ioasid_install_capacity(ioasid_t total);
>  #else /* !CONFIG_IOASID */
>  static inline ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min,
>  				    ioasid_t max, void *private)
> @@ -72,5 +72,8 @@ static inline int ioasid_set_data(ioasid_t ioasid, void
> *data)
>  	return -ENOTSUPP;
>  }
> 
> +static inline void ioasid_install_capacity(ioasid_t total)
> +{
> +}
>  #endif /* CONFIG_IOASID */
>  #endif /* __LINUX_IOASID_H */
> --
> 2.7.4