[PATCH 00/12] iommufd: Add nesting infrastructure

Yi Liu
2023-03-09T08:09:40Z

Nested translation is a hardware feature that is supported by many modern
IOMMU hardwares. It has two stages (stage-1, stage-2) address translation
to get access to the physical address. stage-1 translation table is owned
by userspace (e.g. by a guest OS), while stage-2 is owned by kernel. Changes
to stage-1 translation table should be followed by an IOTLB invalidation.

Take Intel VT-d as an example, the stage-1 translation table is I/O page
table. As the below diagram shows, guest I/O page table pointer in GPA
(guest physical address) is passed to host and be used to perform the stage-1
address translation. Along with it, modifications to present mappings in the
guest I/O page table should be followed with an IOTLB invalidation.

.-------------. .---------------------------.
| vIOMMU | | Guest I/O page table |
| | '---------------------------'
.----------------/
| PASID Entry |--- PASID cache flush --+
'-------------' |
| | V
| | I/O page table pointer in GPA
'-------------'
Guest
------| Shadow |--------------------------|--------
v v v
Host
.-------------. .------------------------.
| pIOMMU | | FS for GIOVA->GPA |
| | '------------------------'
.----------------/ |
| PASID Entry | V (Nested xlate)
'----------------\.----------------------------------.
| | | SS for GPA->HPA, unmanaged domain|
| | '----------------------------------'
'-------------'
Where:
- FS = First stage page tables
- SS = Second stage page tables
<Intel VT-d Nested translation>

In IOMMUFD, all the translation tables are tracked by hw_pagetable (hwpt)
and each has an iommu_domain allocated from iommu driver. So in this series
hw_pagetable and iommu_domain means the same thing if no special note.
IOMMUFD has already supported allocating hw_pagetable that is linked with
an IOAS. However, nesting requires IOMMUFD to allow allocating hw_pagetable
with driver specific parameters and interface to sync stage-1 IOTLB as user
owns the stage-1 translation table.

This series is based on the iommu hw info reporting series [1]. It first
introduces new iommu op for allocating domains with user data and the op
for syncing stage-1 IOTLB, and then extend the IOMMUFD internal infrastructure
to accept user_data and parent hwpt, then relay the data to iommu core to
allocate iommu_domain. After it, extend the ioctl IOMMU_HWPT_ALLOC to accept
user data and stage-2 hwpt ID to allocate hwpt. Along with it, ioctl
IOMMU_HWPT_INVALIDATE is added to invalidate stage-1 IOTLB. This is needed
for user-managed hwpts. ioctl IOMMU_DEVICE_GET_HW_INFO is extended to report
the supported hwpt types bitmap to user. Selftest is added as well to cover
the new ioctls.

Complete code can be found in [2], QEMU could can be found in [3].

At last, this is a team work together with Nicolin Chen, Lu Baolu. Thanks
them for the help. ^_^. Look forward to your feedbacks.

base-commit: 3dfe670c94c7fc4af42e5c08cdd8a110b594e18e

[1] https://lore.kernel.org/linux-iommu/20230309075358.571567-1-yi.l.liu@intel.com/
[2] https://github.com/yiliu1765/iommufd/tree/iommufd_nesting
[3] https://github.com/yiliu1765/qemu/tree/wip/iommufd_rfcv3%2Bnesting

Thanks,
Yi Liu

Lu Baolu (2):
iommu: Add new iommu op to create domains owned by userspace
iommu: Add nested domain support

Nicolin Chen (5):
iommufd/hw_pagetable: Do not populate user-managed hw_pagetables
iommufd/selftest: Add domain_alloc_user() support in iommu mock
iommufd/selftest: Add coverage for IOMMU_HWPT_ALLOC with user data
iommufd/selftest: Add IOMMU_TEST_OP_MD_CHECK_IOTLB test op
iommufd/selftest: Add coverage for IOMMU_HWPT_INVALIDATE ioctl

Yi Liu (5):
iommufd/hw_pagetable: Use domain_alloc_user op for domain allocation
iommufd: Pass parent hwpt and user_data to
iommufd_hw_pagetable_alloc()
iommufd: IOMMU_HWPT_ALLOC allocation with user data
iommufd: Add IOMMU_HWPT_INVALIDATE
iommufd/device: Report supported hwpt_types

drivers/iommu/iommufd/device.c | 9 +-
drivers/iommu/iommufd/hw_pagetable.c | 242 +++++++++++++++++-
drivers/iommu/iommufd/iommufd_private.h | 16 +-
drivers/iommu/iommufd/iommufd_test.h | 30 +++
drivers/iommu/iommufd/main.c | 7 +-
drivers/iommu/iommufd/selftest.c | 104 +++++++-
include/linux/iommu.h | 11 +
include/uapi/linux/iommufd.h | 65 +++++
tools/testing/selftests/iommu/iommufd.c | 126 ++++++++-
tools/testing/selftests/iommu/iommufd_utils.h | 71 +++++
10 files changed, 654 insertions(+), 27 deletions(-)

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2.34.1