RE: [PATCH 05/10] iommu/ioasid: Create an IOASID set for host SVA use

[Tian, Kevin]

> From: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Sent: Thursday, March 26, 2020 1:55 AM
> 
> Bare metal SVA allocates IOASIDs for native process addresses. This
> should be separated from VM allocated IOASIDs thus under its own set.

A curious question. Now bare metal SVA uses the system set and guest
SVA uses dynamically-created set. Then do we still allow ioasid_alloc
with a NULL set pointer?

> 
> This patch creates a system IOASID set with its quota set to PID_MAX.
> This is a reasonable default in that SVM capable devices can only bind
> to limited user processes.
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> ---
>  drivers/iommu/intel-iommu.c | 8 +++++++-
>  drivers/iommu/ioasid.c      | 9 +++++++++
>  include/linux/ioasid.h      | 9 +++++++++
>  3 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index ec3fc121744a..af7a1ef7b31e 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -3511,8 +3511,14 @@ static int __init init_dmars(void)
>  		goto free_iommu;
> 
>  	/* PASID is needed for scalable mode irrespective to SVM */
> -	if (intel_iommu_sm)
> +	if (intel_iommu_sm) {
>  		ioasid_install_capacity(intel_pasid_max_id);
> +		/* We should not run out of IOASIDs at boot */
> +		if (ioasid_alloc_system_set(PID_MAX_DEFAULT)) {
> +			pr_err("Failed to enable host PASID allocator\n");
> +			intel_iommu_sm = 0;
> +		}
> +	}
> 
>  	/*
>  	 * for each drhd
> diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
> index 6265d2dbbced..9135af171a7c 100644
> --- a/drivers/iommu/ioasid.c
> +++ b/drivers/iommu/ioasid.c
> @@ -39,6 +39,9 @@ struct ioasid_data {
>  static ioasid_t ioasid_capacity;
>  static ioasid_t ioasid_capacity_avail;
> 
> +int system_ioasid_sid;
> +static DECLARE_IOASID_SET(system_ioasid);
> +
>  /* System capacity can only be set once */
>  void ioasid_install_capacity(ioasid_t total)
>  {
> @@ -51,6 +54,12 @@ void ioasid_install_capacity(ioasid_t total)
>  }
>  EXPORT_SYMBOL_GPL(ioasid_install_capacity);
> 
> +int ioasid_alloc_system_set(int quota)
> +{
> +	return ioasid_alloc_set(&system_ioasid, quota, &system_ioasid_sid);
> +}
> +EXPORT_SYMBOL_GPL(ioasid_alloc_system_set);
> +
>  /*
>   * 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 8c82d2625671..097b1cc043a3 100644
> --- a/include/linux/ioasid.h
> +++ b/include/linux/ioasid.h
> @@ -29,6 +29,9 @@ struct ioasid_allocator_ops {
>  	void *pdata;
>  };
> 
> +/* Shared IOASID set for reserved for host system use */
> +extern int system_ioasid_sid;
> +
>  #define DECLARE_IOASID_SET(name) struct ioasid_set name = { 0 }
> 
>  #if IS_ENABLED(CONFIG_IOASID)
> @@ -41,6 +44,7 @@ int ioasid_register_allocator(struct ioasid_allocator_ops
> *allocator);
>  void ioasid_unregister_allocator(struct ioasid_allocator_ops *allocator);
>  int ioasid_attach_data(ioasid_t ioasid, void *data);
>  void ioasid_install_capacity(ioasid_t total);
> +int ioasid_alloc_system_set(int quota);
>  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);
> @@ -88,5 +92,10 @@ static inline void ioasid_install_capacity(ioasid_t total)
>  {
>  }
> 
> +static inline int ioasid_alloc_system_set(int quota)
> +{
> +	return -ENOTSUPP;
> +}
> +
>  #endif /* CONFIG_IOASID */
>  #endif /* __LINUX_IOASID_H */
> --
> 2.7.4