Re: [PATCH v7 1/9] iommu: Introduce a union to struct iommu_resv_region

[Robin Murphy <robin.murphy@arm.com>]

On 2021-08-05 09:07, Shameer Kolothum wrote:
> A union is introduced to struct iommu_resv_region to hold
> any firmware specific data. This is in preparation to add
> support for IORT RMR reserve regions and the union now holds
> the RMR specific information.
> 
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> ---
>   include/linux/iommu.h | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 32d448050bf7..bd0e4641c569 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -114,6 +114,13 @@ enum iommu_resv_type {
>   	IOMMU_RESV_SW_MSI,
>   };
>   
> +struct iommu_iort_rmr_data {
> +#define IOMMU_RMR_REMAP_PERMITTED	(1 << 0)
> +	u32 flags;
> +	u32 sid;	/* Stream Id associated with RMR entry */
> +	void *smmu;	/* Associated IORT SMMU node pointer */
> +};

Do we really need to duplicate all this data? AFAICS we could just save 
the acpi_iort_rmr pointer in the iommu_resv_region (with a forward 
declaration here if necessary) and defer parsing its actual mappings 
until the point where we can directly consume the results.

Robin.

> +
>   /**
>    * struct iommu_resv_region - descriptor for a reserved memory region
>    * @list: Linked list pointers
> @@ -121,6 +128,7 @@ enum iommu_resv_type {
>    * @length: Length of the region in bytes
>    * @prot: IOMMU Protection flags (READ/WRITE/...)
>    * @type: Type of the reserved region
> + * @rmr: ACPI IORT RMR specific data
>    */
>   struct iommu_resv_region {
>   	struct list_head	list;
> @@ -128,6 +136,9 @@ struct iommu_resv_region {
>   	size_t			length;
>   	int			prot;
>   	enum iommu_resv_type	type;
> +	union {
> +		struct iommu_iort_rmr_data rmr;
> +	} fw_data;
>   };
>   
>   /**
>