Merge patch series "IOMMUFD Generic interface"

Jason Gunthorpe <[email protected]> says:

==================
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 IO page tables, for ARM, x86 and S390
 - Kernel bypassed 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

Many of these HW features exist to support VM use cases - for instance the
combination of PASID, PRI and Userspace IO Page Tables allows an
implementation of DMA Shared Virtual Addressing (vSVA) within a
guest. Dirty tracking enables VM live migration with SRIOV devices and
PASID support allow creating "scalable IOV" devices, among other things.

As these features are fundamental to a VM platform they need to be
uniformly exposed to all the driver families that do DMA into VMs, which
is currently VFIO and VDPA.

The pre-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 an improved 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 and supports existing qemu based VM flows.

Several follow-on series are being prepared:

- Patches integrating with qemu in native mode:
  https://github.com/yiliu1765/qemu/commits/qemu-iommufd-6.0-rc2

- A completed integration with VFIO now exists that covers "emulated" mdev
  use cases now, and can pass testing with qemu/etc in compatability mode:
  https://github.com/jgunthorpe/linux/commits/vfio_iommufd

- A draft providing system iommu dirty tracking on top of iommufd,
  including iommu driver implementations:
  https://github.com/jpemartins/linux/commits/x86-iommufd

  This pairs with patches for providing a similar API to support VFIO-device
  tracking to give a complete vfio solution:
  https://lore.kernel.org/kvm/[email protected]/

- Userspace page tables aka 'nested translation' for ARM and Intel iommu
  drivers:
  https://github.com/nicolinc/iommufd/commits/iommufd_nesting

- "device centric" vfio series to expose the vfio_device FD directly as a
  normal cdev, and provide an extended API allowing dynamically changing
  the IOAS binding:
  https://github.com/yiliu1765/iommufd/commits/iommufd-v6.0-rc2-nesting-0901

- Drafts for PASID and PRI interfaces are included above as well

Overall enough work is done now to show the merit of the new API design
and at least draft solutions to many of the main problems.

Several people have contributed directly to this work: Eric Auger, Joao
Martins, 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!

The v1/v2 iommufd series has been used to guide a large amount of preparatory
work that has now been merged. The general theme is to organize things in
a way that makes injecting iommufd natural:

 - VFIO live migration support with mlx5 and hisi_acc drivers.
   These series need a dirty tracking solution to be really usable.
   https://lore.kernel.org/kvm/[email protected]/
   https://lore.kernel.org/kvm/[email protected]/

 - Significantly rework the VFIO gvt mdev and remove struct
   mdev_parent_ops
   https://lore.kernel.org/lkml/[email protected]/

 - Rework how PCIe no-snoop blocking works
   https://lore.kernel.org/kvm/[email protected]/

 - Consolidate dma ownership into the iommu core code
   https://lore.kernel.org/linux-iommu/[email protected]/

 - Make all vfio driver interfaces use struct vfio_device consistently
   https://lore.kernel.org/kvm/[email protected]/

 - Remove the vfio_group from the kvm/vfio interface
   https://lore.kernel.org/kvm/[email protected]/

 - Simplify locking in vfio
   https://lore.kernel.org/kvm/[email protected]/

 - Remove the vfio notifiter scheme that faces drivers
   https://lore.kernel.org/kvm/[email protected]/

 - Improve the driver facing API for vfio pin/unpin pages to make the
   presence of struct page clear
   https://lore.kernel.org/kvm/[email protected]/

 - Clean up in the Intel IOMMU driver
   https://lore.kernel.org/linux-iommu/[email protected]/
   https://lore.kernel.org/linux-iommu/[email protected]/
   https://lore.kernel.org/linux-iommu/[email protected]/
   https://lore.kernel.org/linux-iommu/[email protected]/
   https://lore.kernel.org/linux-iommu/[email protected]/

 - Rework s390 vfio drivers
   https://lore.kernel.org/kvm/[email protected]/

 - Normalize vfio ioctl handling
   https://lore.kernel.org/kvm/[email protected]/

 - VFIO API for dirty tracking (aka dma logging) managed inside a PCI
   device, with mlx5 implementation
   https://lore.kernel.org/kvm/[email protected]

 - Introduce a struct device sysfs presence for struct vfio_device
   https://lore.kernel.org/kvm/[email protected]/

 - Complete restructuring the vfio mdev model
   https://lore.kernel.org/kvm/[email protected]/

 - Isolate VFIO container code in preperation for iommufd to provide an
   alternative implementation of it all
   https://lore.kernel.org/kvm/[email protected]

 - Simplify and consolidate iommu_domain/device compatability checking
   https://lore.kernel.org/linux-iommu/[email protected]/

 - Align iommu SVA support with the domain-centric model
   https://lore.kernel.org/all/[email protected]/

This is about 233 patches applied since March, thank you to everyone
involved in all this work!

Currently there are a number of supporting series still in progress:

 - DMABUF exporter support for VFIO to allow PCI P2P with VFIO
   https://lore.kernel.org/r/[email protected]

 - Start to provide iommu_domain ops for POWER
   https://lore.kernel.org/all/[email protected]/

However, these are not necessary for this series to advance.

Syzkaller coverage has been merged and is now running in the syzbot
environment on linux-next:

https://github.com/google/syzkaller/pull/3515
https://github.com/google/syzkaller/pull/3521
==================

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jason Gunthorpe <[email protected]>

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