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

Yi Liu
2023-09-19T09:25:36Z

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_v1

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 | 20 ++++++++++++
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 | 16 ++++++++++
include/linux/iommu.h | 8 +++++
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, 111 insertions(+), 18 deletions(-)

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2.34.1