> -----Original Message----- > From: Nathan Chen <[email protected]> > Sent: 17 February 2026 23:20 > To: [email protected] > Cc: Shameer Kolothum Thodi <[email protected]>; Nicolin Chen > <[email protected]>; Nathan Chen <[email protected]>; Matt Ochs > <[email protected]> > Subject: [RFC PATCH 1/3] qemu: Support NVIDIA Tegra241 CMDQV for > SMMUv3 > > From: Nathan Chen <[email protected]> > > Introduce support for a "cmdqv" IOMMU attribute which enables > NVIDIA Tegra241 CMDQV, an extension for ARM SMMUv3. This > supports passthrough of physical SMMU-CMDQ linked command > queue from host space to a VM.
Currently the v2 QEMU vCMDQ series uses the "tegra241-cmdqv" property to enable NVIDIA Tegra241 CMDQV. There is a suggestion to change this to a generic "cmdqv" property and probe the host CMDQV extension type from the kernel. Also, plan is to change it to ON_OFF_AUTO format like the suggestion for other properties like ril and ats etc I am currently looking into that. From a libvirt point of view, not sure this will have much impact, but just a heads up. Thanks, Shameer > Signed-off-by: Nathan Chen <[email protected]> > --- > docs/formatdomain.rst | 6 ++++++ > src/conf/domain_conf.c | 15 +++++++++++++++ > src/conf/domain_conf.h | 1 + > src/conf/domain_validate.c | 5 ++++- > src/conf/schemas/domaincommon.rng | 5 +++++ > src/qemu/qemu_command.c | 1 + > 6 files changed, 32 insertions(+), 1 deletion(-) > > diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst > index 82788c15a2..74431838ff 100644 > --- a/docs/formatdomain.rst > +++ b/docs/formatdomain.rst > @@ -9341,6 +9341,12 @@ Examples: > The ``pciBus`` attribute notes the index of the controller that an > IOMMU device is attached to. (QEMU/KVM and ``smmuv3`` model only) > > + ``cmdqv`` > + The ``cmdqv`` attribute with possible values ``on`` and ``off`` can be > used > + to enable NVIDIA Tegra241 CMDQV, an extension for ARM SMMUv3 that > supports > + passthrough of physical SMMU-CMDQ linked command queue from host > space to VM. > + :since:`Since 12.1.0` (QEMU/KVM and ``smmuv3`` model only) > + > In case of ``virtio`` IOMMU device, the ``driver`` element can optionally > contain ``granule`` subelement that allows to choose which granule will be > used by default. It is useful when running guests with different page size > diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c > index 453e301041..6385420c10 100644 > --- a/src/conf/domain_conf.c > +++ b/src/conf/domain_conf.c > @@ -14680,6 +14680,10 @@ > virDomainIOMMUDefParseXML(virDomainXMLOption *xmlopt, > &iommu->pci_bus, -1) < 0) > return NULL; > > + if (virXMLPropTristateSwitch(driver, "cmdqv", VIR_XML_PROP_NONE, > + &iommu->cmdqv) < 0) > + return NULL; > + > if ((granule = virXPathNode("./driver/granule", ctxt))) { > g_autofree char *mode = virXMLPropString(granule, "mode"); > unsigned long long size; > @@ -16781,6 +16785,7 @@ virDomainIOMMUDefEquals(const > virDomainIOMMUDef *a, > a->iotlb != b->iotlb || > a->aw_bits != b->aw_bits || > a->dma_translation != b->dma_translation || > + a->cmdqv != b->cmdqv || > a->granule != b->granule) > return false; > > @@ -22537,6 +22542,12 @@ > virDomainIOMMUDefCheckABIStability(virDomainIOMMUDef *src, > dst->pci_bus, src->pci_bus); > return false; > } > + if (src->cmdqv != dst->cmdqv) { > + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, > + _("Target domain IOMMU device cmdqv value '%1$d' does > not > match source '%2$d'"), > + dst->cmdqv, src->cmdqv); > + return false; > + } > if (src->dma_translation != dst->dma_translation) { > virReportError(VIR_ERR_CONFIG_UNSUPPORTED, > _("Target domain IOMMU device dma translation '%1$s' > does not > match source '%2$s'"), > @@ -28941,6 +28952,10 @@ virDomainIOMMUDefFormat(virBuffer *buf, > virBufferAsprintf(&driverAttrBuf, " pciBus='%d'", > iommu->pci_bus); > } > + if (iommu->cmdqv != VIR_TRISTATE_SWITCH_ABSENT) { > + virBufferAsprintf(&driverAttrBuf, " cmdqv='%s'", > + virTristateSwitchTypeToString(iommu->cmdqv)); > + } > if (iommu->granule != 0) { > if (iommu->granule == -1) { > virBufferAddLit(&driverChildBuf, "<granule mode='host'/>\n"); > diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h > index a13f6d79e9..41dba29a4f 100644 > --- a/src/conf/domain_conf.h > +++ b/src/conf/domain_conf.h > @@ -3075,6 +3075,7 @@ struct _virDomainIOMMUDef { > virTristateSwitch xtsup; > virTristateSwitch pt; > int granule; /* -1 means 'host', 0 unset, page size in KiB otherwise */ > + virTristateSwitch cmdqv; > }; > > typedef enum { > diff --git a/src/conf/domain_validate.c b/src/conf/domain_validate.c > index 1ad614935f..cac5dabf06 100644 > --- a/src/conf/domain_validate.c > +++ b/src/conf/domain_validate.c > @@ -3208,7 +3208,8 @@ virDomainIOMMUDefValidate(const > virDomainIOMMUDef *iommu) > iommu->eim != VIR_TRISTATE_SWITCH_ABSENT || > iommu->iotlb != VIR_TRISTATE_SWITCH_ABSENT || > iommu->dma_translation != VIR_TRISTATE_SWITCH_ABSENT || > - iommu->pci_bus >= 0) { > + iommu->pci_bus >= 0 || > + iommu->cmdqv != VIR_TRISTATE_SWITCH_ABSENT) { > virReportError(VIR_ERR_XML_ERROR, > _("iommu model '%1$s' doesn't support some > additional > attributes"), > virDomainIOMMUModelTypeToString(iommu->model)); > @@ -3231,6 +3232,7 @@ virDomainIOMMUDefValidate(const > virDomainIOMMUDef *iommu) > iommu->aw_bits != 0 || > iommu->dma_translation != VIR_TRISTATE_SWITCH_ABSENT || > iommu->pci_bus >= 0 || > + iommu->cmdqv != VIR_TRISTATE_SWITCH_ABSENT || > iommu->granule != 0) { > virReportError(VIR_ERR_XML_ERROR, > _("iommu model '%1$s' doesn't support some > additional > attributes"), > @@ -3243,6 +3245,7 @@ virDomainIOMMUDefValidate(const > virDomainIOMMUDef *iommu) > if (iommu->pt != VIR_TRISTATE_SWITCH_ABSENT || > iommu->xtsup != VIR_TRISTATE_SWITCH_ABSENT || > iommu->pci_bus >= 0 || > + iommu->cmdqv != VIR_TRISTATE_SWITCH_ABSENT || > iommu->granule != 0) { > virReportError(VIR_ERR_XML_ERROR, > _("iommu model '%1$s' doesn't support some > additional > attributes"), > diff --git a/src/conf/schemas/domaincommon.rng > b/src/conf/schemas/domaincommon.rng > index dafbdc63e7..2677207ae4 100644 > --- a/src/conf/schemas/domaincommon.rng > +++ b/src/conf/schemas/domaincommon.rng > @@ -6352,6 +6352,11 @@ > <data type="unsignedInt"/> > </attribute> > </optional> > + <optional> > + <attribute name="cmdqv"> > + <ref name="virOnOff"/> > + </attribute> > + </optional> > <optional> > <element name="granule"> > <choice> > diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c > index a742998e4c..3735387ebd 100644 > --- a/src/qemu/qemu_command.c > +++ b/src/qemu/qemu_command.c > @@ -6330,6 +6330,7 @@ qemuBuildPCINestedSmmuv3DevProps(const > virDomainDef *def, > "s:driver", "arm-smmuv3", > "s:primary-bus", bus, > "s:id", iommu->info.alias, > + "B:tegra241-cmdqv", (iommu->cmdqv == > VIR_TRISTATE_SWITCH_ON), > NULL) < 0) > return NULL; > > -- > 2.43.0
