RE: [PATCH v3 02/17] iommu: Add nested domain support

[Tian, Kevin]

> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Sent: Monday, July 24, 2023 7:04 PM
> 
> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> 
> Introduce a new domain type for a user I/O page table, which is nested
> on top of another user space address represented by a UNMANAGED
> domain. The
> mappings of a nested domain are managed by user space software,
> therefore
> it's unnecessary to have map/unmap callbacks. But the updates of the PTEs
> in the nested domain page table must be propagated to the caches on both
> IOMMU (IOTLB) and devices (DevTLB).
> 
> The nested domain is allocated by the domain_alloc_user op, and attached
> to the device through the existing iommu_attach_device/group() interfaces.
> 
> A new domain op, named cache_invalidate_user is added for the userspace
> to
> flush the hardware caches for a nested domain through iommufd. No
> wrapper
> for it, as it's only supposed to be used by iommufd.
> 
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Co-developed-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>