On a Wednesday in 2025, Nathan Chen via Devel wrote:
Introduce support for "pciBus" driver attribute for
"smmuv3" IOMMU model. The "pciBus" attribute indicates
the index of the controller that a smmuv3 IOMMU device
is attached to, and differentiates the device-pluggable
arm-smmuv3 model from the virt-machine-associated smmuv3
model.
Signed-off-by: Nathan Chen <[email protected]>
---
docs/formatdomain.rst | 4 ++
src/conf/domain_conf.c | 16 +++++++
src/conf/domain_conf.h | 1 +
src/conf/domain_validate.c | 28 ++++++++++--
src/conf/schemas/domaincommon.rng | 5 ++
src/qemu/qemu_command.c | 76 ++++++++++++++++++++++++++++---
6 files changed, 121 insertions(+), 9 deletions(-)
diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index 4c245f41a9..a181462d13 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -9238,6 +9238,10 @@ Example:
Enable x2APIC mode. Useful for higher number of guest CPUs.
:since:`Since 11.5.0` (QEMU/KVM and ``amd`` model only)
+ ``pciBus``
+ The ``pciBus`` attribute notes the index of the controller that an
+ IOMMU device is attached to. (QEMU/KVM and ``smmuv3`` model only)
+
The ``virtio`` IOMMU devices can further have ``address`` element as
described
in `Device addresses`_ (address has to by type of ``pci``).
diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/
domaincommon.rng
index ae3fa95904..9afc679258 100644
--- a/src/conf/schemas/domaincommon.rng
+++ b/src/conf/schemas/domaincommon.rng
@@ -6322,6 +6322,11 @@
<ref name="virOnOff"/>
</attribute>
</optional>
+ <optional>
+ <attribute name="pciBus">
+ <data type="unsignedInt"/>
+ </attribute>
+ </optional>
</element>
</optional>
<optional>
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 97fe4267ec..ad749afc41 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -6239,6 +6239,62 @@ qemuBuildBootCommandLine(virCommand *cmd,
}
+static virJSONValue *
+qemuBuildPCINestedSmmuv3DevProps(const virDomainDef *def,
+ const virDomainIOMMUDef *iommu,
+ size_t id)
+{
+ g_autoptr(virJSONValue) props = NULL;
+ g_autofree char *bus = NULL;
+ g_autofree char *smmuv3_id = NULL;
+ size_t i;
+
+ for (i = 0; i < def->ncontrollers; i++) {
+ virDomainControllerDef *cont = def->controllers[i];
+ if (cont->idx == iommu->pci_bus) {
+ if (cont->type == VIR_DOMAIN_CONTROLLER_TYPE_PCI) {
+ const char *alias = cont->info.alias;
+
+ if (!alias)
+ return NULL;
+
+ if (virDomainDeviceAliasIsUserAlias(alias)) {
+ if (cont->model ==
VIR_DOMAIN_CONTROLLER_MODEL_PCI_ROOT &&
+ iommu->pci_bus == 0) {
+ if (qemuDomainSupportsPCIMultibus(def))
+ bus = g_strdup("pci.0");
+ else
+ bus = g_strdup("pci");
+ } else if (cont->model ==
VIR_DOMAIN_CONTROLLER_MODEL_PCIE_ROOT) {
+ bus = g_strdup("pcie.0");
+ }
+ } else {
+ bus = g_strdup(alias);
+ }
+ break;
+ }
+ }
+ }
This duplicates parts of 'qemuBuildDeviceAddressPCIGetBus'
+
+ if (!bus) {
+ virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+ _("Could not find a suitable controller for
smmuv3."));
+ return NULL;
+ }
+
+ smmuv3_id = g_strdup_printf("smmuv3.%zu", id);
+
+ if (virJSONValueObjectAdd(&props,
+ "s:driver", "arm-smmuv3",
+ "s:primary-bus", bus,
+ "s:id", smmuv3_id,
+ NULL) < 0)
+ return NULL;
+
+ return g_steal_pointer(&props);
+}
+
+
static int
qemuBuildIOMMUCommandLine(virCommand *cmd,
const virDomainDef *def,
@@ -6286,9 +6342,6 @@ qemuBuildIOMMUCommandLine(virCommand *cmd,
return -1;
return 0;
- case VIR_DOMAIN_IOMMU_MODEL_SMMUV3:
- /* There is no -device for SMMUv3, so nothing to be done
here */
- return 0;
case VIR_DOMAIN_IOMMU_MODEL_AMD:
if (virJSONValueObjectAdd(&wrapperProps,
@@ -6318,6 +6371,17 @@ qemuBuildIOMMUCommandLine(virCommand *cmd,
return 0;
+ case VIR_DOMAIN_IOMMU_MODEL_SMMUV3:
+ if (iommu->pci_bus >= 0) {
+ if (!(props = qemuBuildPCINestedSmmuv3DevProps(def,
iommu, i)))
+ return -1;
+ if (qemuBuildDeviceCommandlineFromJSON(cmd, props,
def, qemuCaps) < 0)
+ return -1;
+ break;
+ } else {
+ return 0;
+ }
No need for the else branch.
+
case VIR_DOMAIN_IOMMU_MODEL_LAST:
default:
virReportEnumRangeError(virDomainIOMMUModel, iommu->model);
@@ -10822,15 +10886,15 @@ qemuBuildCommandLine(virDomainObj *vm,
if (qemuBuildBootCommandLine(cmd, def) < 0)
return NULL;
- if (qemuBuildIOMMUCommandLine(cmd, def, qemuCaps) < 0)
- return NULL;
-
if (qemuBuildGlobalControllerCommandLine(cmd, def) < 0)
return NULL;
if (qemuBuildControllersCommandLine(cmd, def, qemuCaps) < 0)
return NULL;
+ if (qemuBuildIOMMUCommandLine(cmd, def, qemuCaps) < 0)
+ return NULL;
+
Formatting the IOMMU devices after the controllers makes sense, but
should be in a separate patch.
if (qemuBuildMemoryDeviceCommandLine(cmd, cfg, def, priv) < 0)
return NULL;
Reviewed-by: Ján Tomko <[email protected]>
