Hi,
On 3/18/22 6:27 PM, Jason Gunthorpe wrote:
> iommufd is the user API to control the IOMMU subsystem as it relates to
> managing IO page tables that point at user space memory.
>
> It takes over from drivers/vfio/vfio_iommu_type1.c (aka the VFIO
> container) which is the VFIO specific interface for a similar idea.
>
> We see a broad need for extended features, some being highly IOMMU device
> specific:
> - Binding iommu_domain's to PASID/SSID
> - Userspace page tables, for ARM, x86 and S390
> - Kernel bypass'd invalidation of user page tables
> - Re-use of the KVM page table in the IOMMU
> - Dirty page tracking in the IOMMU
> - Runtime Increase/Decrease of IOPTE size
> - PRI support with faults resolved in userspace
This series does not have any concept of group fds anymore and the API
is device oriented.
I have a question wrt pci bus reset capability.
8b27ee60bfd6 ("vfio-pci: PCI hot reset interface")
introduced VFIO_DEVICE_PCI_GET_HOT_RESET_INFO and VFIO_DEVICE_PCI_HOT_RESET
Maybe we can reuse VFIO_DEVICE_GET_PCI_HOT_RESET_INFO to retrieve the devices
and iommu groups that need to be checked and involved in the bus reset. If I
understand correctly we now need to make sure the devices are handled in the
same security context (bound to the same iommufd)
however VFIO_DEVICE_PCI_HOT_RESET operate on a collection of group fds.
How do you see the porting of this functionality onto /dev/iommu?
Thanks
Eric
>
> As well as a need to access these features beyond just VFIO, VDPA for
> instance, but other classes of accelerator HW are touching on these areas
> now too.
>
> The v1 series proposed re-using the VFIO type 1 data structure, however it
> was suggested that if we are doing this big update then we should also
> come with a data structure that solves the limitations that VFIO type1
> has. Notably this addresses:
>
> - Multiple IOAS/'containers' and multiple domains inside a single FD
>
> - Single-pin operation no matter how many domains and containers use
> a page
>
> - A fine grained locking scheme supporting user managed concurrency for
> multi-threaded map/unmap
>
> - A pre-registration mechanism to optimize vIOMMU use cases by
> pre-pinning pages
>
> - Extended ioctl API that can manage these new objects and exposes
> domains directly to user space
>
> - domains are sharable between subsystems, eg VFIO and VDPA
>
> The bulk of this code is a new data structure design to track how the
> IOVAs are mapped to PFNs.
>
> iommufd intends to be general and consumable by any driver that wants to
> DMA to userspace. From a driver perspective it can largely be dropped in
> in-place of iommu_attach_device() and provides a uniform full feature set
> to all consumers.
>
> As this is a larger project this series is the first step. This series
> provides the iommfd "generic interface" which is designed to be suitable
> for applications like DPDK and VMM flows that are not optimized to
> specific HW scenarios. It is close to being a drop in replacement for the
> existing VFIO type 1.
>
> This is part two of three for an initial sequence:
> - Move IOMMU Group security into the iommu layer
>
> https://lore.kernel.org/linux-iommu/[email protected]/
> * Generic IOMMUFD implementation
> - VFIO ability to consume IOMMUFD
> An early exploration of this is available here:
> https://github.com/luxis1999/iommufd/commits/iommufd-v5.17-rc6
>
> Various parts of the above extended features are in WIP stages currently
> to define how their IOCTL interface should work.
>
> At this point, using the draft VFIO series, unmodified qemu has been
> tested to operate using iommufd on x86 and ARM systems.
>
> Several people have contributed directly to this work: Eric Auger, Kevin
> Tian, Lu Baolu, Nicolin Chen, Yi L Liu. Many more have participated in the
> discussions that lead here, and provided ideas. Thanks to all!
>
> This is on github: https://github.com/jgunthorpe/linux/commits/iommufd
>
> # S390 in-kernel page table walker
> Cc: Niklas Schnelle <[email protected]>
> Cc: Matthew Rosato <[email protected]>
> # AMD Dirty page tracking
> Cc: Joao Martins <[email protected]>
> # ARM SMMU Dirty page tracking
> Cc: Keqian Zhu <[email protected]>
> Cc: Shameerali Kolothum Thodi <[email protected]>
> # ARM SMMU nesting
> Cc: Eric Auger <[email protected]>
> Cc: Jean-Philippe Brucker <[email protected]>
> # Map/unmap performance
> Cc: Daniel Jordan <[email protected]>
> # VDPA
> Cc: "Michael S. Tsirkin" <[email protected]>
> Cc: Jason Wang <[email protected]>
> # Power
> Cc: David Gibson <[email protected]>
> # vfio
> Cc: Alex Williamson <[email protected]>
> Cc: Cornelia Huck <[email protected]>
> Cc: [email protected]
> # iommu
> Cc: [email protected]
> # Collaborators
> Cc: "Chaitanya Kulkarni" <[email protected]>
> Cc: Nicolin Chen <[email protected]>
> Cc: Lu Baolu <[email protected]>
> Cc: Kevin Tian <[email protected]>
> Cc: Yi Liu <[email protected]>
> Signed-off-by: Jason Gunthorpe <[email protected]>
>
> Jason Gunthorpe (11):
> interval-tree: Add a utility to iterate over spans in an interval tree
> iommufd: File descriptor, context, kconfig and makefiles
> kernel/user: Allow user::locked_vm to be usable for iommufd
> iommufd: PFN handling for iopt_pages
> iommufd: Algorithms for PFN storage
> iommufd: Data structure to provide IOVA to PFN mapping
> iommufd: IOCTLs for the io_pagetable
> iommufd: Add a HW pagetable object
> iommufd: Add kAPI toward external drivers
> iommufd: vfio container FD ioctl compatibility
> iommufd: Add a selftest
>
> Kevin Tian (1):
> iommufd: Overview documentation
>
> Documentation/userspace-api/index.rst | 1 +
> .../userspace-api/ioctl/ioctl-number.rst | 1 +
> Documentation/userspace-api/iommufd.rst | 224 +++
> MAINTAINERS | 10 +
> drivers/iommu/Kconfig | 1 +
> drivers/iommu/Makefile | 2 +-
> drivers/iommu/iommufd/Kconfig | 22 +
> drivers/iommu/iommufd/Makefile | 13 +
> drivers/iommu/iommufd/device.c | 274 ++++
> drivers/iommu/iommufd/hw_pagetable.c | 142 ++
> drivers/iommu/iommufd/io_pagetable.c | 890 +++++++++++
> drivers/iommu/iommufd/io_pagetable.h | 170 +++
> drivers/iommu/iommufd/ioas.c | 252 ++++
> drivers/iommu/iommufd/iommufd_private.h | 231 +++
> drivers/iommu/iommufd/iommufd_test.h | 65 +
> drivers/iommu/iommufd/main.c | 346 +++++
> drivers/iommu/iommufd/pages.c | 1321 +++++++++++++++++
> drivers/iommu/iommufd/selftest.c | 495 ++++++
> drivers/iommu/iommufd/vfio_compat.c | 401 +++++
> include/linux/interval_tree.h | 41 +
> include/linux/iommufd.h | 50 +
> include/linux/sched/user.h | 2 +-
> include/uapi/linux/iommufd.h | 223 +++
> kernel/user.c | 1 +
> lib/interval_tree.c | 98 ++
> tools/testing/selftests/Makefile | 1 +
> tools/testing/selftests/iommu/.gitignore | 2 +
> tools/testing/selftests/iommu/Makefile | 11 +
> tools/testing/selftests/iommu/config | 2 +
> tools/testing/selftests/iommu/iommufd.c | 1225 +++++++++++++++
> 30 files changed, 6515 insertions(+), 2 deletions(-)
> create mode 100644 Documentation/userspace-api/iommufd.rst
> create mode 100644 drivers/iommu/iommufd/Kconfig
> create mode 100644 drivers/iommu/iommufd/Makefile
> create mode 100644 drivers/iommu/iommufd/device.c
> create mode 100644 drivers/iommu/iommufd/hw_pagetable.c
> create mode 100644 drivers/iommu/iommufd/io_pagetable.c
> create mode 100644 drivers/iommu/iommufd/io_pagetable.h
> create mode 100644 drivers/iommu/iommufd/ioas.c
> create mode 100644 drivers/iommu/iommufd/iommufd_private.h
> create mode 100644 drivers/iommu/iommufd/iommufd_test.h
> create mode 100644 drivers/iommu/iommufd/main.c
> create mode 100644 drivers/iommu/iommufd/pages.c
> create mode 100644 drivers/iommu/iommufd/selftest.c
> create mode 100644 drivers/iommu/iommufd/vfio_compat.c
> create mode 100644 include/linux/iommufd.h
> create mode 100644 include/uapi/linux/iommufd.h
> create mode 100644 tools/testing/selftests/iommu/.gitignore
> create mode 100644 tools/testing/selftests/iommu/Makefile
> create mode 100644 tools/testing/selftests/iommu/config
> create mode 100644 tools/testing/selftests/iommu/iommufd.c
>
>
> base-commit: d1c716ed82a6bf4c35ba7be3741b9362e84cd722
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