Re: [Qemu-devel] [PATCH v2 01/13] iommu: Add IOMMU index concept to IOMMU API

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> If an IOMMU supports mappings that care about the memory
> transaction attributes, then it no longer has a unique
> address -> output mapping, but more than one. We can
> represent these using an IOMMU index, analogous to TCG's
> mmu indexes.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  include/exec/memory.h | 55 +++++++++++++++++++++++++++++++++++++++++++
>  memory.c              | 23 ++++++++++++++++++
>  2 files changed, 78 insertions(+)
>
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index eb2ba065195..fa6e98ee7be 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -206,6 +206,20 @@ enum IOMMUMemoryRegionAttr {
>   * to report whenever mappings are changed, by calling
>   * memory_region_notify_iommu() (or, if necessary, by calling
>   * memory_region_notify_one() for each registered notifier).
> + *
> + * Conceptually an IOMMU provides a mapping from input address
> + * to an output TLB entry. If the IOMMU is aware of memory transaction
> + * attributes and the output TLB entry depends on the transaction
> + * attributes, we represent this using IOMMU indexes. Each index
> + * selects a particular translation table that the IOMMU has:
> + *   @attrs_to_index returns the IOMMU index for a set of transaction attributes
> + *   @translate takes an input address and an IOMMU index
> + * and the mapping returned can only depend on the input address and the
> + * IOMMU index.
> + *
> + * Most IOMMUs don't care about the transaction attributes and support
> + * only a single IOMMU index. A more complex IOMMU might have one index
> + * for secure transactions and one for non-secure transactions.
>   */
>  typedef struct IOMMUMemoryRegionClass {
>      /* private */
> @@ -290,6 +304,29 @@ typedef struct IOMMUMemoryRegionClass {
>       */
>      int (*get_attr)(IOMMUMemoryRegion *iommu, enum IOMMUMemoryRegionAttr attr,
>                      void *data);
> +
> +    /* Return the IOMMU index to use for a given set of transaction attributes.
> +     *
> +     * Optional method: if an IOMMU only supports a single IOMMU index then
> +     * the default implementation of memory_region_iommu_attrs_to_index()
> +     * will return 0.
> +     *
> +     * The indexes supported by an IOMMU must be contiguous, starting at 0.
> +     *
> +     * @iommu: the IOMMUMemoryRegion
> +     * @attrs: memory transaction attributes
> +     */
> +    int (*attrs_to_index)(IOMMUMemoryRegion *iommu, MemTxAttrs attrs);
> +
> +    /* Return the number of IOMMU indexes this IOMMU supports.
> +     *
> +     * Optional method: if this method is not provided, then
> +     * memory_region_iommu_num_indexes() will return 1, indicating that
> +     * only a single IOMMU index is supported.
> +     *
> +     * @iommu: the IOMMUMemoryRegion
> +     */
> +    int (*num_indexes)(IOMMUMemoryRegion *iommu);
>  } IOMMUMemoryRegionClass;
>
>  typedef struct CoalescedMemoryRange CoalescedMemoryRange;
> @@ -1054,6 +1091,24 @@ int memory_region_iommu_get_attr(IOMMUMemoryRegion *iommu_mr,
>                                   enum IOMMUMemoryRegionAttr attr,
>                                   void *data);
>
> +/**
> + * memory_region_iommu_attrs_to_index: return the IOMMU index to
> + * use for translations with the given memory transaction attributes.
> + *
> + * @iommu_mr: the memory region
> + * @attrs: the memory transaction attributes
> + */
> +int memory_region_iommu_attrs_to_index(IOMMUMemoryRegion *iommu_mr,
> +                                       MemTxAttrs attrs);
> +
> +/**
> + * memory_region_iommu_num_indexes: return the total number of IOMMU
> + * indexes that this IOMMU supports.
> + *
> + * @iommu_mr: the memory region
> + */
> +int memory_region_iommu_num_indexes(IOMMUMemoryRegion *iommu_mr);
> +
>  /**
>   * memory_region_name: get a memory region's name
>   *
> diff --git a/memory.c b/memory.c
> index 3212acc7f49..64f4a55d546 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -1915,6 +1915,29 @@ int memory_region_iommu_get_attr(IOMMUMemoryRegion *iommu_mr,
>      return imrc->get_attr(iommu_mr, attr, data);
>  }
>
> +int memory_region_iommu_attrs_to_index(IOMMUMemoryRegion *iommu_mr,
> +                                       MemTxAttrs attrs)
> +{
> +    IOMMUMemoryRegionClass *imrc = IOMMU_MEMORY_REGION_GET_CLASS(iommu_mr);
> +
> +    if (!imrc->attrs_to_index) {
> +        return 0;
> +    }
> +
> +    return imrc->attrs_to_index(iommu_mr, attrs);
> +}
> +
> +int memory_region_iommu_num_indexes(IOMMUMemoryRegion *iommu_mr)
> +{
> +    IOMMUMemoryRegionClass *imrc = IOMMU_MEMORY_REGION_GET_CLASS(iommu_mr);
> +
> +    if (!imrc->num_indexes) {
> +        return 1;
> +    }
> +
> +    return imrc->num_indexes(iommu_mr);
> +}
> +
>  void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client)
>  {
>      uint8_t mask = 1 << client;


--
Alex Bennée