[Qemu-devel] [RFC v2 0/4] AMBA platform device passthrough

[Alvise Rigo <a.rigo@virtualopensystems.com>]

These patches are the next iteration of "[Qemu-devel] [RFC 0/4] AMBA
platform device passthrough" and are based on the latest version of VFIO
for platform devices "[RFC PATCH v5 00/11] VFIO support for platform
devices" and the initial patch series "[Qemu-devel] [RFC v2 0/6] KVM
platform device passthrough".

- [PATCH 1/4] Addition of the exec flag to the DMA mappings. At the
  moment this is mandatory only for the ARM SMMU.
  Change since v1:
  Thanks to the new version of the VFIO API, now we can know from the
  kernel if the IOMMU requires the EXEC_FLAG.  For now, we always add it
  if supported.

- [PATCH 2/4] Possibility to bind a wider class of devices. In
  particular the patch proposes a solution to enhance a bit the device
  tree nodes generation, allowing to specify more than one compatibility
  property (handy for AMBA devices). This was required by the DMA330
  that needs "arm,pl330","arm,primecell" as compatibility string,
  together with a clock source defined in the device tree. In the future
  VFIO will be able to tell if we are dealing with an AMBA device;
  before that, we have to rely on the compatibility string to state
  that.

- [PATCH 3/4] Another approach to handle the EOI, starting from the
  assumption that we know in advance the location of the interrupt clear
  register of the device. This is of course another workaround and not
  the definitive solution until we can rely on a proper callback from
  the VGIC (something that we will see in a future version of VFIO for
  platform devices).
  Change since v1:
  The code is much simpler now and does not require the definition of an
  additional memory region which would be dma-mapped by the memory
  listener vfio_listener_region_add in hw/vfio/common.c. In this regard
  probably soon or later we will need a way to exclude some regions from
  being mapped "blindly" by the memory listener: this is for example
  what happens with the memory region of the device which is dma-mapped
  to itself.

- [PATCH 4/4] If event_notifier_init fails to create a new eventfd, it
  will fallback usign pipe/pipe2 and we end up passing to the kernel a
  wrong file descriptor. This patch force to check if eventfd has been
  used.

In order to easy the test of the VFIO API with platform devices, here:
https://github.com/virtualopensystems/vfio-host-test.git
is possible to find a handy test suite for an ARM host which will print the
devices that could be probed with VFIO and run some basic tests on a chosen
device. If the ARM DMA330 is tested, a device specific code (which was
introduced in the Virtual Open Systems guide
http://virtualopensystems.com/en/solutions/guides/vfio-on-arm) will be run to
verify even further the correct behaviour of the device. This suite has been
tested with ARM FastModels.

Alvise Rigo (4):
  Add EXEC_FLAG to VFIO DMA mappings
  Add AMBA devices support to VFIO
  MemoryRegion with EOI callbacks for VFIO Platform devices
  Always use eventfd as notifying mechanism

 hw/arm/virt.c              | 39 ++++++++++++++++---
 hw/vfio/common.c           |  9 +++++
 hw/vfio/platform.c         | 96 +++++++++++++++++++++++++++++++++++++++++++++-
 hw/vfio/vfio-common.h      |  1 +
 linux-headers/linux/vfio.h |  2 +
 5 files changed, 140 insertions(+), 7 deletions(-)

-- 
1.9.1