[PATCH v7 0/7] KVM PCIe/MSI passthrough on ARM/ARM64: kernel part 3/3: vfio changes

Eric Auger
2016-04-19T17:25:09Z

This series allows the user-space to register a reserved IOVA domain.
This completes the kernel integration of the whole functionality on top
of part 1 & 2.

We reuse the VFIO DMA MAP ioctl with a new flag to bridge to the
dma-reserved-iommu API. The number of IOVA pages to provision for MSI
binding is reported through the VFIO_IOMMU_GET_INFO iotcl.

vfio_iommu_type1 checks if the MSI mapping is safe when attaching the
vfio group to the container (allow_unsafe_interrupts modality).

On ARM/ARM64, the IOMMU does not astract IRQ remapping. the modality is
abstracted on MSI controller side. The GICv3 ITS is the first controller
advertising the modality.

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

Best Regards

Eric

Testing:
- functional on ARM64 AMD Overdrive HW (single GICv2m frame) with
Intel X540-T2 (SR-IOV capable)
- Not tested: ARM GICv3 ITS

References:
[1] [RFC 0/2] VFIO: Add virtual MSI doorbell support
(https://lkml.org/lkml/2015/7/24/135)
[2] [RFC PATCH 0/6] vfio: Add interface to map MSI pages
(https://lists.cs.columbia.edu/pipermail/kvmarm/2015-September/016607.html)
[3] [PATCH v2 0/3] Introduce MSI hardware mapping for VFIO
(http://permalink.gmane.org/gmane.comp.emulators.kvm.arm.devel/3858)

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

previous version at
https://git.linaro.org/people/eric.auger/linux.git/shortlog/refs/heads/v4.6-rc1-pcie-passthrough-v6

QEMU Integration:
[RFC v2 0/8] KVM PCI/MSI passthrough with mach-virt
(http://lists.gnu.org/archive/html/qemu-arm/2016-01/msg00444.html)
https://git.linaro.org/people/eric.auger/qemu.git/shortlog/refs/heads/v2.5.0-pci-passthrough-rfc-v2

History:

v6 -> v7:
- vfio_find_dma now accepts a dma_type argument.
- should have recovered the capability to unmap the whole user IOVA range
- remove computation of nb IOVA pages -> will post a separate RFC for that
while respinning the QEMU part

RFC v5 -> patch v6:
- split to ease the review process

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 (7):
vfio: introduce a vfio_dma type field
vfio/type1: vfio_find_dma accepting a type argument
vfio/type1: specialize remove_dma and replay according to type
vfio: allow reserved iova registration
vfio/type1: also check IRQ remapping capability at msi domain
iommu/arm-smmu: do not advertise IOMMU_CAP_INTR_REMAP
vfio/type1: return MSI mapping requirements with VFIO_IOMMU_GET_INFO

drivers/iommu/arm-smmu-v3.c | 3 +-
drivers/iommu/arm-smmu.c | 3 +-
drivers/vfio/vfio_iommu_type1.c | 297 ++++++++++++++++++++++++++++++++++++++--
include/uapi/linux/vfio.h | 12 +-
4 files changed, 298 insertions(+), 17 deletions(-)

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1.9.1