Merge tag 'for-linus-iommufd' of git://git.kernel.org/pub/scm/linux/kernel/git/jgg/iommufd

Pull iommufd updates from Jason Gunthorpe:
 "This broadly brings the assigned HW command queue support to iommufd.
  This feature is used to improve SVA performance in VMs by avoiding
  paravirtualization traps during SVA invalidations.

  Along the way I think some of the core logic is in a much better state
  to support future driver backed features.

  Summary:

   - IOMMU HW now has features to directly assign HW command queues to a
     guest VM. In this mode the command queue operates on a limited set
     of invalidation commands that are suitable for improving guest
     invalidation performance and easy for the HW to virtualize.

     This brings the generic infrastructure to allow IOMMU drivers to
     expose such command queues through the iommufd uAPI, mmap the
     doorbell pages, and get the guest physical range for the command
     queue ring itself.

   - An implementation for the NVIDIA SMMUv3 extension "cmdqv" is built
     on the new iommufd command queue features. It works with the
     existing SMMU driver support for cmdqv in guest VMs.

   - Many precursor cleanups and improvements to support the above
     cleanly, changes to the general ioctl and object helpers, driver
     support for VDEVICE, and mmap pgoff cookie infrastructure.

   - Sequence VDEVICE destruction to always happen before VFIO device
     destruction. When using the above type features, and also in future
     confidential compute, the internal virtual device representation
     becomes linked to HW or CC TSM configuration and objects. If a VFIO
     device is removed from iommufd those HW objects should also be
     cleaned up to prevent a sort of UAF. This became important now that
     we have HW backing the VDEVICE.

   - Fix one syzkaller found error related to math overflows during iova
     allocation"

* tag 'for-linus-iommufd' of git://git.kernel.org/pub/scm/linux/kernel/git/jgg/iommufd: (57 commits)
  iommu/arm-smmu-v3: Replace vsmmu_size/type with get_viommu_size
  iommu/arm-smmu-v3: Do not bother impl_ops if IOMMU_VIOMMU_TYPE_ARM_SMMUV3
  iommufd: Rename some shortterm-related identifiers
  iommufd/selftest: Add coverage for vdevice tombstone
  iommufd/selftest: Explicitly skip tests for inapplicable variant
  iommufd/vdevice: Remove struct device reference from struct vdevice
  iommufd: Destroy vdevice on idevice destroy
  iommufd: Add a pre_destroy() op for objects
  iommufd: Add iommufd_object_tombstone_user() helper
  iommufd/viommu: Roll back to use iommufd_object_alloc() for vdevice
  iommufd/selftest: Test reserved regions near ULONG_MAX
  iommufd: Prevent ALIGN() overflow
  iommu/tegra241-cmdqv: import IOMMUFD module namespace
  iommufd: Do not allow _iommufd_object_alloc_ucmd if abort op is set
  iommu/tegra241-cmdqv: Add IOMMU_VEVENTQ_TYPE_TEGRA241_CMDQV support
  iommu/tegra241-cmdqv: Add user-space use support
  iommu/tegra241-cmdqv: Do not statically map LVCMDQs
  iommu/tegra241-cmdqv: Simplify deinit flow in tegra241_cmdqv_remove_vintf()
  iommu/tegra241-cmdqv: Use request_threaded_irq
  iommu/arm-smmu-v3-iommufd: Add hw_info to impl_ops
  ...

1 files changed, 12 insertions, 0 deletions

diff --git a/Documentation/userspace-api/iommufd.rst b/Documentation/userspace-api/iommufd.rst
index b0df15865dec..03f7510384d2 100644
--- a/Documentation/userspace-api/iommufd.rst
+++ b/Documentation/userspace-api/iommufd.rst
@@ -124,6 +124,17 @@ Following IOMMUFD objects are exposed to userspace:
   used to allocate a vEVENTQ. Each vIOMMU can support multiple types of vEVENTS,
   but is confined to one vEVENTQ per vEVENTQ type.
 
+- IOMMUFD_OBJ_HW_QUEUE, representing a hardware accelerated queue, as a subset
+  of IOMMU's virtualization features, for the IOMMU HW to directly read or write
+  the virtual queue memory owned by a guest OS. This HW-acceleration feature can
+  allow VM to work with the IOMMU HW directly without a VM Exit, so as to reduce
+  overhead from the hypercalls. Along with the HW QUEUE object, iommufd provides
+  user space an mmap interface for VMM to mmap a physical MMIO region from the
+  host physical address space to the guest physical address space, allowing the
+  guest OS to directly control the allocated HW QUEUE. Thus, when allocating a
+  HW QUEUE, the VMM must request a pair of mmap info (offset/length) and pass in
+  exactly to an mmap syscall via its offset and length arguments.
+
 All user-visible objects are destroyed via the IOMMU_DESTROY uAPI.
 
 The diagrams below show relationships between user-visible objects and kernel
@@ -270,6 +281,7 @@ User visible objects are backed by following datastructures:
 - iommufd_viommu for IOMMUFD_OBJ_VIOMMU.
 - iommufd_vdevice for IOMMUFD_OBJ_VDEVICE.
 - iommufd_veventq for IOMMUFD_OBJ_VEVENTQ.
+- iommufd_hw_queue for IOMMUFD_OBJ_HW_QUEUE.
 
 Several terminologies when looking at these datastructures: