Re: [PATCH 00/20] iommu: Refactoring domain allocation interface

[Yi Liu]

On 2024/5/29 13:32, Lu Baolu wrote:
> The IOMMU subsystem has undergone some changes, including the removal
> of iommu_ops from the bus structure. Consequently, the existing domain
> allocation interface, which relies on a bus type argument, is no longer
> relevant:
>
>      struct iommu_domain *iommu_domain_alloc(struct bus_type *bus)
>
> This series is designed to refactor the use of this interface. It
> proposes two new interfaces to replace iommu_domain_alloc():
>
> - iommu_user_domain_alloc(): This interface is intended for allocating
>    iommu domains managed by userspace for device passthrough scenarios,
>    such as those used by iommufd, vfio, and vdpa. It clearly indicates
>    that the domain is for user-managed device DMA.

user paging domain? It looks to me user domain includes the nested domains
as well.

>    If an IOMMU driver does not implement iommu_ops->domain_alloc_user,
>    this interface will rollback to the generic paging domain allocation.
>
> - iommu_paging_domain_alloc(): This interface is for allocating iommu
>    domains managed by kernel drivers for kernel DMA purposes. It takes a
>    device pointer as a parameter, which better reflects the current
>    design of the IOMMU subsystem.
>
> The majority of device drivers currently using iommu_domain_alloc() do
> so to allocate a domain for a specific device and then attach that
> domain to the device. These cases can be straightforwardly migrated to
> the new interfaces.
>
> However, there are some drivers with more complex use cases that do
> not fit neatly into this new scheme. For example:
>
> $ git grep "= iommu_domain_alloc"
> arch/arm/mm/dma-mapping.c:      mapping->domain = iommu_domain_alloc(bus);
> drivers/gpu/drm/rockchip/rockchip_drm_drv.c:    private->domain = iommu_domain_alloc(private->iommu_dev->bus);
> drivers/gpu/drm/tegra/drm.c:            tegra->domain = iommu_domain_alloc(&platform_bus_type);
> drivers/infiniband/hw/usnic/usnic_uiom.c:       pd->domain = domain = iommu_domain_alloc(dev->bus);
>
> This series leave those cases unchanged and keep iommu_domain_alloc()
> for their usage. But new drivers should not use it anymore.

does it mean there is still domains allocated via iommu_domain_alloc()
on VT-d platform?

> The whole series is also available on GitHub:
> https://github.com/LuBaolu/intel-iommu/commits/iommu-domain-allocation-refactor-v1
>
> Lu Baolu (20):
>    iommu: Add iommu_user_domain_alloc() interface
>    iommufd: Use iommu_user_domain_alloc()
>    vfio/type1: Use iommu_paging_domain_alloc()
>    vhost-vdpa: Use iommu_user_domain_alloc()
>    iommu: Add iommu_paging_domain_alloc() interface
>    drm/msm: Use iommu_paging_domain_alloc()
>    drm/nouveau/tegra: Use iommu_paging_domain_alloc()
>    gpu: host1x: Use iommu_paging_domain_alloc()
>    media: nvidia: tegra: Use iommu_paging_domain_alloc()
>    media: venus: firmware: Use iommu_paging_domain_alloc()
>    ath10k: Use iommu_paging_domain_alloc()
>    wifi: ath11k: Use iommu_paging_domain_alloc()
>    remoteproc: Use iommu_paging_domain_alloc()
>    soc/fsl/qbman: Use iommu_paging_domain_alloc()
>    iommu/vt-d: Add helper to allocate paging domain
>    iommu/vt-d: Add domain_alloc_paging support
>    iommu/vt-d: Simplify compatibility check for identity domain
>    iommu/vt-d: Enhance compatibility check for paging domain attach
>    iommu/vt-d: Remove domain_update_iommu_cap()
>    iommu/vt-d: Remove domain_update_iommu_superpage()
>
>   include/linux/iommu.h                         |  12 +
>   drivers/gpu/drm/msm/msm_iommu.c               |   8 +-
>   .../drm/nouveau/nvkm/engine/device/tegra.c    |   4 +-
>   drivers/gpu/host1x/dev.c                      |   6 +-
>   drivers/iommu/intel/iommu.c                   | 319 ++++++++----------
>   drivers/iommu/intel/pasid.c                   |  28 +-
>   drivers/iommu/iommu.c                         |  62 ++++
>   drivers/iommu/iommufd/hw_pagetable.c          |  20 +-
>   .../media/platform/nvidia/tegra-vde/iommu.c   |   6 +-
>   drivers/media/platform/qcom/venus/firmware.c  |   6 +-
>   drivers/net/wireless/ath/ath10k/snoc.c        |   6 +-
>   drivers/net/wireless/ath/ath11k/ahb.c         |   6 +-
>   drivers/remoteproc/remoteproc_core.c          |   6 +-
>   drivers/soc/fsl/qbman/qman_portal.c           |   4 +-
>   drivers/vfio/vfio_iommu_type1.c               |   7 +-
>   drivers/vhost/vdpa.c                          |  11 +-
>   16 files changed, 253 insertions(+), 258 deletions(-)

--
Regards,
Yi Liu