Re: [PATCH v5 02/13] iommufd: Introduce IOMMUFD_OBJ_VIOMMU and its related struct

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Oct 25, 2024 at 04:49:42PM -0700, Nicolin Chen wrote:
> Add a new IOMMUFD_OBJ_VIOMMU with an iommufd_viommu structure to represent
> a slice of physical IOMMU device passed to or shared with a user space VM.
> This slice, now a vIOMMU object, is a group of virtualization resources of
> a physical IOMMU's, such as:
>  - Security namespace for guest owned ID, e.g. guest-controlled cache tags
>  - Access to a sharable nesting parent pagetable across physical IOMMUs
>  - Virtualization of various platforms IDs, e.g. RIDs and others
>  - Delivery of paravirtualized invalidation
>  - Direct assigned invalidation queues
>  - Direct assigned interrupts
>  - Non-affiliated event reporting
> 
> Add a new viommu_alloc op in iommu_ops, for drivers to allocate their own
> vIOMMU structures. And this allocation also needs a free(), so add struct
> iommufd_viommu_ops.
> 
> To simplify a vIOMMU allocation, provide a iommufd_viommu_alloc() helper.
> It's suggested that a driver should embed a core-level viommu structure in
> its driver-level viommu struct and call the iommufd_viommu_alloc() helper,
> meanwhile the driver can also implement a viommu ops:
>     struct my_driver_viommu {
>         struct iommufd_viommu core;
>         /* driver-owned properties/features */
>         ....
>     };
> 
>     static const struct iommufd_viommu_ops my_driver_viommu_ops = {
>         .free = my_driver_viommu_free,
>         /* future ops for virtualization features */
>         ....
>     };
> 
>     static struct iommufd_viommu my_driver_viommu_alloc(...)
>     {
>         struct my_driver_viommu *my_viommu =
>                 iommufd_viommu_alloc(ictx, my_driver_viommu, core,
>                                      my_driver_viommu_ops);
>         /* Init my_viommu and related HW feature */
>         ....
>         return &my_viommu->core;
>     }
> 
>     static struct iommu_domain_ops my_driver_domain_ops = {
>         ....
>         .viommu_alloc = my_driver_viommu_alloc,
>     };
> 
> To make the Kernel config work between a driver and the iommufd core, move
> the _iommufd_object_alloc helper into a new driver.c file that builds with
> CONFIG_IOMMUFD_DRIVER.
> 
> Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
>  drivers/iommu/iommufd/Makefile          |  2 +-
>  drivers/iommu/iommufd/iommufd_private.h |  4 --
>  include/linux/iommu.h                   | 14 +++++++
>  include/linux/iommufd.h                 | 53 +++++++++++++++++++++++++
>  drivers/iommu/iommufd/driver.c          | 38 ++++++++++++++++++
>  drivers/iommu/iommufd/main.c            | 32 ---------------
>  6 files changed, 106 insertions(+), 37 deletions(-)
>  create mode 100644 drivers/iommu/iommufd/driver.c

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason