[PATCH v2 0/6] iommufd support allocating nested parent domain

[Yi Liu]

IOMMU hardwares that support nested translation would have two stages
address translation (normally mentioned as stage-1 and stage-2). The page
table formats of the stage-1 and stage-2 can be different. e.g., VT-d has
different page table formats for stage-1 and stage-2.

Nested parent domain is the iommu domain used to represent the stage-2
translation. In IOMMUFD, both stage-1 and stage-2 translation are tracked
as HWPT (a.k.a. iommu domain). Stage-2 HWPT is parent of stage-1 HWPT as
stage-1 cannot work alone in nested translation. In the cases of stage-1 and
stage-2 page table format are different, the parent HWPT should use exactly
the stage-2 page table format. However, the existing kernel hides the format
selection in iommu drivers, so the domain allocated via IOMMU_HWPT_ALLOC can
use either stage-1 page table format or stage-2 page table format, there is
no guarantees for it.

To enforce the page table format of the nested parent domain, this series
introduces a new iommu op (domain_alloc_user) which can accept user flags
to allocate domain as userspace requires. It also converts IOMMUFD to use
the new domain_alloc_user op for domain allocation if supported, then extends
the IOMMU_HWPT_ALLOC ioctl to pass down a NEST_PARENT flag to allocate a HWPT
which can be used as parent. This series implements the new op in Intel iommu
driver to have a complete picture. It is a preparation for adding nesting
support in IOMMUFD/IOMMU.

Complete code can be found:
https://github.com/yiliu1765/iommufd/tree/iommufd_alloc_user_v2

Change log:

v2:
 - Require domain_alloc_user op if IOMMU_HWPT_ALLOC passes non-zero flags (Kevin)
 - IOMMUFD core should check kernel known flags while iommu driver needs
   to check supported flags as well (Jason)
 - Minor tweaks per Baolu's comment

v1: https://lore.kernel.org/linux-iommu/20230919092523.39286-1-yi.l.liu@xxxxxxxxx/

Regards,
	Yi Liu

Yi Liu (6):
  iommu: Add new iommu op to create domains owned by userspace
  iommufd/hw_pagetable: Use domain_alloc_user op for domain allocation
  iommufd/hw_pagetable: Accepts user flags for domain allocation
  iommufd/hw_pagetable: Support allocating nested parent domain
  iommufd/selftest: Add domain_alloc_user() support in iommu mock
  iommu/vt-d: Add domain_alloc_user op

 drivers/iommu/intel/iommu.c                   | 28 +++++++++++++++++
 drivers/iommu/iommufd/device.c                |  2 +-
 drivers/iommu/iommufd/hw_pagetable.c          | 31 ++++++++++++++-----
 drivers/iommu/iommufd/iommufd_private.h       |  3 +-
 drivers/iommu/iommufd/selftest.c              | 19 ++++++++++++
 include/linux/iommu.h                         | 11 ++++++-
 include/uapi/linux/iommufd.h                  | 12 ++++++-
 tools/testing/selftests/iommu/iommufd.c       | 24 +++++++++++---
 .../selftests/iommu/iommufd_fail_nth.c        |  2 +-
 tools/testing/selftests/iommu/iommufd_utils.h | 11 +++++--
 10 files changed, 124 insertions(+), 19 deletions(-)

-- 
2.34.1