On 3/9/26 8:21 PM, Nathan Chen wrote:
> Hi,
>
> This series introduces support for specifying 'auto' for arm-smmuv3
> accelerated mode's ATS, RIL, SSIDSIZE, and OAS feature properties.
> When set to 'auto', these feature values are derived directly from
> host IOMMU capabilities, avoiding the need for management layers to
> introspect host settings.
>
> Accelerated SMMUv3 Address Translation Services support is derived
> from IDR0, Range Invalidation support is derived from IDR3, Substream
> ID size is derived from IDR1, and output address space is derived from
> IDR5.
>
> Additionally, an OnOffAuto "ats" property is added for vfio-pci devices,
> where setting 'auto' detects the per-device presence of
> IOMMU_HW_CAP_PCI_ATS_NOT_SUPPORTED from the kernel, and the ATS cap can
> be advertised or hidden by setting 'on' or 'off'. This is dependent
> on Shameer's recent kernel series for reporting effective ATS support
> status [0].
>
> The default values are set to 'auto' for all properties.
>
> A complete branch can be found here:
> https://github.com/NathanChenNVIDIA/qemu/tree/smmuv3-accel-auto
I have just noticed we are missing documentation for smmuv3 accel options in
qemu-options.hx
At the moment we just have:
``-device arm-smmuv3,primary-bus=id``
This is only supported by ``-machine virt`` (ARM).
``primary-bus=id``
Accepts either the default root complex (pcie.0) or a
pxb-pcie based root complex.
Eric
>
> Please take a look and let me know your feedback.
>
> Thanks,
> Nathan
>
> Example usage:
> qemu-system-aarch64 \
> -object iommufd,id=iommufd0 \
> -machine virt,accel=kvm,gic-version=3,ras=on,highmem-mmio-size=4T \
> -cpu host -smp cpus=4 -m size=16G -nographic \
> -object memory-backend-ram,size=16G,id=m0 \
> -numa node,memdev=m0,cpus=0-3,nodeid=0 \
> -numa node,nodeid=1 -numa node,nodeid=2 -numa node,nodeid=3 -numa node,nodeid=4 \
> -numa node,nodeid=5 -numa node,nodeid=6 -numa node,nodeid=7 -numa node,nodeid=8 \
> -device pxb-pcie,id=pcie.1,bus_nr=1,bus=pcie.0,numa_node=0 \
> -device arm-smmuv3,primary-bus=pcie.1,id=smmuv3.1,accel=on,ats=auto,ssidsize=auto,ril=auto,oas=auto \
> -device pcie-root-port,id=pcie.port1,bus=pcie.1,chassis=1,io-reserve=0 \
> -device vfio-pci-nohotplug,host=0009:06:00.0,bus=pcie.port1,rombar=0,id=dev0,iommufd=iommufd0,ats=auto \
> -object acpi-generic-initiator,id=gi0,pci-dev=dev0,node=1 \
> -object acpi-generic-initiator,id=gi1,pci-dev=dev0,node=2 \
> -object acpi-generic-initiator,id=gi2,pci-dev=dev0,node=3 \
> -object acpi-generic-initiator,id=gi3,pci-dev=dev0,node=4 \
> -object acpi-generic-initiator,id=gi4,pci-dev=dev0,node=5 \
> -object acpi-generic-initiator,id=gi5,pci-dev=dev0,node=6 \
> -object acpi-generic-initiator,id=gi6,pci-dev=dev0,node=7 \
> -object acpi-generic-initiator,id=gi7,pci-dev=dev0,node=8 \
> -bios /usr/share/AAVMF/AAVMF_CODE.fd \
> -device nvme,drive=nvme0,serial=deadbeaf1,bus=pcie.0 \
> -drive file=/var/lib/libvirt/images/guest.qcow2,index=0,media=disk,format=qcow2,if=none,id=nvme0 \
> -device e1000,romfile=/usr/local/share/qemu/efi-e1000.rom,netdev=net0,bus=pcie.0 \
> -netdev user,id=net0,hostfwd=tcp::5558-:22,hostfwd=tcp::5586-:5586
>
> The properties may also be omitted as they are set to auto by default:
>
> -device arm-smmuv3,primary-bus=pcie.1,id=smmuv3.1,accel=on \
> -device vfio-pci-nohotplug,host=0009:06:00.0,bus=pcie.port1,rombar=0,id=dev0,iommufd=iommufd0 \
>
> Testing:
> Basic sanity testing was performed on an NVIDIA Grace platform with GPU
> device assignment and running CUDA test apps on the guest. Observed the
> feature properties being set based on host IOMMU capabilities and the
> ATS capability for a vfio-pci device reported based on what was reported
> from the host. Additional testing and feedback are welcome.
>
> [0] https://lore.kernel.org/all/20260303150348.233997-1-skolothumtho@nvidia.com/#r
>
> Nathan Chen (8):
> hw/arm/smmuv3-accel: Add helper for resolving auto parameters
> hw/arm/smmuv3-accel: Introduce _AUTO support for ATS
> vfio/pci: Add ats property and mask ATS cap when not exposed
> hw/arm/smmuv3-accel: Introduce _AUTO support for RIL
> qdev: Add a SsidSizeMode property
> hw/arm/smmuv3-accel: Introduce _AUTO support for SSID size
> qdev: Add an OasMode property
> hw/arm/smmuv3-accel: Introduce _AUTO support for OAS
>
> backends/iommufd.c | 15 +++
> hw/arm/smmuv3-accel.c | 118 ++++++++++++++++++++---
> hw/arm/smmuv3-accel.h | 2 +
> hw/arm/smmuv3.c | 43 +++++----
> hw/arm/virt-acpi-build.c | 2 +-
> hw/core/qdev-properties-system.c | 27 ++++++
> hw/vfio/pci.c | 63 ++++++++++++
> hw/vfio/pci.h | 1 +
> include/hw/arm/smmuv3.h | 9 +-
> include/hw/core/qdev-properties-system.h | 6 ++
> include/system/host_iommu_device.h | 10 ++
> qapi/misc-arm.json | 31 ++++++
> qapi/pragma.json | 1 +
> 13 files changed, 292 insertions(+), 36 deletions(-)
>