[PATCH v7 00/10] KVM PCIe/MSI passthrough on ARM/ARM64: kernel part 1/3: iommu changes

[Eric Auger]

This series introduces the dma-reserved-iommu api used to:

- create/destroy an iova domain dedicated to reserved iova bindings
- map/unmap physical addresses onto reserved IOVAs.
- search for an existing reserved iova mapping matching a PA window
- determine whether an msi needs to be iommu mapped
- translate an msi_msg PA address into its IOVA counterpart

Currently reserved IOVAs are meant to map MSI physical doorbells. A single
reserved domain does exit per domain.

Also a new domain attribute is introduced to signal whether the MSI
addresses must be mapped in the IOMMU.

In current usage:
VFIO subsystem is supposed to create/destroy the iommu reserved domain.
The MSI layer is supposed to allocate/free iova mappings

Since several drivers are likely to use the same doorbell, a reference
counting takes place on the bindings. An RB-tree indexed by PA is used
to easily lookup for existing mappings at MSI message composition time.

More details & context can be found at:
http://www.linaro.org/blog/core-dump/kvm-pciemsi-passthrough-armarm64/

Best Regards

Eric

Git: complete series available at
https://git.linaro.org/people/eric.auger/linux.git/shortlog/refs/heads/v4.6-rc4-pcie-passthrough-v7

History:

v6 -> v7:
- fixed known lock bugs and multiple page sized slots matching
  (I currently only have a single MSI frame made of a single page)
- reserved_iova_cookie now pointing to a struct that encapsulates the
  iova domain handle + protection attribute passed from VFIO (Alex' req)
- 2 new functions exposed: iommu_msi_mapping_translate_msg,
  iommu_msi_mapping_desc_to_domain: not sure this is the right location/proto
  though
- iommu_put_reserved_iova now takes a phys_addr_t
- everything now is cleanup on iommu_domain destruction

RFC v5 -> patch v6:
- split to ease the review process
- in dma-reserved-api use a spin lock instead of a mutex (reported by
  Jean-Philippe)
- revisit iommu_get_reserved_iova API to pass a size parameter upon
  Marc's request
- Consistently use the page order passed when creating the iova domain.
- init reserved_binding_list (reported by Julien)

RFC v4 -> RFC v5:
- take into account Thomas' comments on MSI related patches
  - split "msi: IOMMU map the doorbell address when needed"
  - increase readability and add comments
  - fix style issues
 - split "iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute"
 - platform ITS now advertises IOMMU_CAP_INTR_REMAP
 - fix compilation issue with CONFIG_IOMMU API unset
 - arm-smmu-v3 now advertises DOMAIN_ATTR_MSI_MAPPING

RFC v3 -> v4:
- Move doorbell mapping/unmapping in msi.c
- fix ref count issue on set_affinity: in case of a change in the address
  the previous address is decremented
- doorbell map/unmap now is done on msi composition. Should allow the use
  case for platform MSI controllers
- create dma-reserved-iommu.h/c exposing/implementing a new API dedicated
  to reserved IOVA management (looking like dma-iommu glue)
- series reordering to ease the review:
  - first part is related to IOMMU
  - second related to MSI sub-system
  - third related to VFIO (except arm-smmu IOMMU_CAP_INTR_REMAP removal)
- expose the number of requested IOVA pages through VFIO_IOMMU_GET_INFO
  [this partially addresses Marc's comments on iommu_get/put_single_reserved
   size/alignment problematic - which I did not ignore - but I don't know
   how much I can do at the moment]

RFC v2 -> RFC v3:
- should fix wrong handling of some CONFIG combinations:
  CONFIG_IOVA, CONFIG_IOMMU_API, CONFIG_PCI_MSI_IRQ_DOMAIN
- fix MSI_FLAG_IRQ_REMAPPING setting in GICv3 ITS (although not tested)

PATCH v1 -> RFC v2:
- reverted to RFC since it looks more reasonable ;-) the code is split
  between VFIO, IOMMU, MSI controller and I am not sure I did the right
  choices. Also API need to be further discussed.
- iova API usage in arm-smmu.c.
- MSI controller natively programs the MSI addr with either the PA or IOVA.
  This is not done anymore in vfio-pci driver as suggested by Alex.
- check irq remapping capability of the group

RFC v1 [2] -> PATCH v1:
- use the existing dma map/unmap ioctl interface with a flag to register a
  reserved IOVA range. Use the legacy Rb to store this special vfio_dma.
- a single reserved IOVA contiguous region now is allowed
- use of an RB tree indexed by PA to store allocated reserved slots
- use of a vfio_domain iova_domain to manage iova allocation within the
  window provided by the userspace
- vfio alloc_map/unmap_free take a vfio_group handle
- vfio_group handle is cached in vfio_pci_device
- add ref counting to bindings
- user modality enabled at the end of the series


Eric Auger (10):
  iommu: Add DOMAIN_ATTR_MSI_MAPPING attribute
  iommu/arm-smmu: advertise DOMAIN_ATTR_MSI_MAPPING attribute
  iommu: introduce a reserved iova cookie
  iommu/dma-reserved-iommu: alloc/free_reserved_iova_domain
  iommu/dma-reserved-iommu: reserved binding rb-tree and helpers
  iommu/dma-reserved-iommu: iommu_get/put_reserved_iova
  iommu/dma-reserved-iommu: delete bindings in
    iommu_free_reserved_iova_domain
  iommu/dma-reserved_iommu: iommu_msi_mapping_desc_to_domain
  iommu/dma-reserved-iommu: iommu_msi_mapping_translate_msg
  iommu/arm-smmu: call iommu_free_reserved_iova_domain on domain
    destruction

 drivers/iommu/Kconfig              |   8 +
 drivers/iommu/Makefile             |   1 +
 drivers/iommu/arm-smmu-v3.c        |   4 +
 drivers/iommu/arm-smmu.c           |   4 +
 drivers/iommu/dma-reserved-iommu.c | 422 +++++++++++++++++++++++++++++++++++++
 drivers/iommu/iommu.c              |   2 +
 include/linux/dma-reserved-iommu.h | 142 +++++++++++++
 include/linux/iommu.h              |   7 +
 8 files changed, 590 insertions(+)
 create mode 100644 drivers/iommu/dma-reserved-iommu.c
 create mode 100644 include/linux/dma-reserved-iommu.h

-- 
1.9.1