By default the virtio-iommu translates MSI transactions. This behavior is inherited from ARM SMMU. However the virt machine code knows where the MSI doorbells are so we can easily declare those regions as VIRTIO_IOMMU_RESV_MEM_T_MSI. With that setting the guest iommu subsystem will not need to map MSIs. This setup will simplify VFIO integration.
In this series, the ITS doorbell is declared as an MSI region to be bypassed by the VIRTIO-IOMMU. This paves the way to the x86 integration where the MSI region [0xFEE00000,0xFEEFFFFF] will be exposed by q35 machine. However this is not part of this series. Best Regards Eric This series can be found at: https://github.com/eauger/qemu/tree/v5.0.0-virtio-iommu-msi-bypass-v1 History: - Most of those patches were respinned from [PATCH for-5.0 v11 00/20] VIRTIO-IOMMU device except the last one which is new Eric Auger (5): qdev: Introduce DEFINE_PROP_RESERVED_REGION virtio-iommu: Implement RESV_MEM probe request virtio-iommu: Handle reserved regions in the translation process virtio-iommu-pci: Add array of Interval properties hw/arm/virt: Let the virtio-iommu bypass MSIs include/exec/memory.h | 6 ++ include/hw/qdev-properties.h | 3 + include/hw/virtio/virtio-iommu.h | 2 + include/qemu/typedefs.h | 1 + hw/arm/virt.c | 5 ++ hw/core/qdev-properties.c | 89 +++++++++++++++++++++++++ hw/virtio/virtio-iommu-pci.c | 3 + hw/virtio/virtio-iommu.c | 109 ++++++++++++++++++++++++++++++- hw/virtio/trace-events | 1 + 9 files changed, 217 insertions(+), 2 deletions(-) -- 2.20.1