On Tue, Aug 18, 2026 at 11:30:09AM -0700, Nathan Chen via Devel wrote:
> Hi,
>
> This is a follow up to the previous patchset [0] for supporting Tegra241
> vCMDQ.
>
> This patchset is tested with Shameer's qemu series for vCMDQ support.
> The accelerated SMMUv3 series for qemu and Libvirt are
> pre-requisites for vCMDQ support, as accelerated SMMUv3 must be enabled
> alongside vCMDQ.
>
> A new 'cmdqv' <iommu> driver attribute is introduced to toggle enabling
> vCMDQ support. For instance, specifying hostdevs associated with
> multiple accelerated SMMUs + CMDQV enabled, configured to be routed to
> pcie-expander-bus controllers in a way where VFIO device to SMMUv3
> associations are matched with the host:
>
> <devices>
> ...
> <controller type='pci' index='1' model='pcie-expander-bus'>
> <model name='pxb-pcie'/>
> <target busNr='252'/>
> <address type='pci' domain='0x0000' bus='0x00' slot='0x01'
> function='0x0'/>
> </controller>
> <controller type='pci' index='2' model='pcie-expander-bus'>
> <model name='pxb-pcie'/>
> <target busNr='248'/>
> <address type='pci' domain='0x0000' bus='0x00' slot='0x02'
> function='0x0'/>
> </controller>
> ...
> <controller type='pci' index='21' model='pcie-root-port'>
> <model name='pcie-root-port'/>
> <target chassis='21' port='0x0'/>
> <address type='pci' domain='0x0000' bus='0x01' slot='0x00'
> function='0x0'/>
> </controller>
> <controller type='pci' index='22' model='pcie-root-port'>
> <model name='pcie-root-port'/>
> <target chassis='22' port='0xa8'/>
> <address type='pci' domain='0x0000' bus='0x02' slot='0x00'
> function='0x0'/>
> </controller>
> ...
> <hostdev mode='subsystem' type='pci' managed='no'>
> <source>
> <address domain='0x0009' bus='0x01' slot='0x00' function='0x0'/>
> </source>
> <address type='pci' domain='0x0000' bus='0x15' slot='0x00'
> function='0x0'/>
> </hostdev>
> <hostdev mode='subsystem' type='pci' managed='no'>
> <source>
> <address domain='0x0019' bus='0x01' slot='0x00' function='0x0'/>
> </source>
> <address type='pci' domain='0x0000' bus='0x16' slot='0x00'
> function='0x0'/>
> </hostdev>
> <iommu model='smmuv3'>
> <driver pciBus='1' accel='on' ats='on' ril='on' ssidsize='20' oas='44'
> cmdqv='on'/>
> </iommu>
> <iommu model='smmuv3'>
> <driver pciBus='2' accel='on' ats='on' ril='on' ssidsize='20' oas='44'
> cmdqv='on'/>
> </iommu>
> </devices>
>
> This would get translated to a qemu command line with the arguments
> below:
>
> -device
> '{"driver":"pxb-pcie","bus_nr":252,"id":"pci.1","bus":"pcie.0","addr":"0x1"}'
> \
> -device
> '{"driver":"pxb-pcie","bus_nr":248,"id":"pci.2","bus":"pcie.0","addr":"0x2"}'
> \
> -device
> '{"driver":"pcie-root-port","port":0,"chassis":21,"id":"pci.21","bus":"pci.1","addr":"0x0"}'
> \
> -device
> '{"driver":"pcie-root-port","port":168,"chassis":22,"id":"pci.22","bus":"pci.2","addr":"0x0"}'
> \
> -device
> '{"driver":"arm-smmuv3","primary-bus":"pci.1","id":"iommu0","accel":true,"ats":true,"cmdqv":"on","ril":true,"pasid":true,"oas":44}'
> \
> -device
> '{"driver":"arm-smmuv3","primary-bus":"pci.2","id":"iommu1","accel":true,"ats":true,"cmdqv":"on","ril":true,"pasid":true,"oas":44}'
> \
> -device
> '{"driver":"vfio-pci","host":"0009:01:00.0","id":"hostdev0","bus":"pci.21","addr":"0x0"}'
> \
> -device
> '{"driver":"vfio-pci","host":"0019:01:00.0","id":"hostdev1","bus":"pci.22","addr":"0x0"}'
> \
>
> This series is on Github:
> https://github.com/NathanChenNVIDIA/libvirt/tree/cmdqv-v4/
>
> Thanks,
> Nathan
>
> Changes from v3:
> - Move qemuValidateDomainDeviceDefIOMMU() check from patch 1 to 2
> - Mention default hypervisor value will be used in formatdomain.rst if
> cmdqv is omitted
> - Make cmdqv virDomainIOMMUDefValidate() check aligned with order of all
> cmdqv checks in the function
> - Include cmdqv for accel validation error message in domain_validate.c
>
> Changes from v2:
> - Add QEMU capabilities support for cmdqv
> - Change QEMU command line parameter to expect OnOffAuto string
>
> Changes from v1:
> - Remove 'identifier' attribute for SMMUv3
> - Change QEMU command line property from 'tegra241-cmdqv' to 'cmdqv'
> - Support QEMU OnOffAuto CMDQV property instead of expecting a bool
>
> [0]
> https://lists.libvirt.org/archives/list/[email protected]/thread/NGSB6ECUQR6RPL7WQQRTNCSDZTSECPLH/
>
> Nathan Chen (3):
> qemu: introduce QEMU_CAPS_ARM_SMMUV3_CMDQV
> qemu: add IOMMU attribute "cmdqv" for smmuv3
> tests: qemuxmlconfdata: provide cmdqv sample XML and CLI args
Reviewed-by: Pavel Hrdina <[email protected]>
