[RFC PATCH 1/7] qemu: add IOMMU model smmuv3Dev

23 Sep 2025

Introduce support for "smmuv3Dev" IOMMU model and
"parentIdx" and "accel" IOMMU device attributes. The
former indicates the index of the controller that a
smmuv3Dev IOMMU device is attached to, while the
latter indicates whether hardware accelerated SMMUv3
support is to be enabled.

Signed-off-by: Nathan Chen <nathanc@nvidia.com>
---
 docs/formatdomain.rst             | 13 +++++-
 src/conf/domain_conf.c            | 35 +++++++++++++++
 src/conf/domain_conf.h            |  3 ++
 src/conf/domain_validate.c        | 26 +++++++++--
 src/conf/schemas/domaincommon.rng | 11 +++++
 src/qemu/qemu_command.c           | 73 +++++++++++++++++++++++++++++--
 src/qemu/qemu_domain_address.c    |  2 +
 src/qemu/qemu_validate.c          | 16 +++++++
 8 files changed, 170 insertions(+), 9 deletions(-)

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index f50dce477f..2f1e06ba0e 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -9161,8 +9161,17 @@ Example:
 ``model``
    Supported values are ``intel`` (for Q35 guests) ``smmuv3``
    (:since:`since 5.5.0`, for ARM virt guests), ``virtio``
-   (:since:`since 8.3.0`, for Q35 and ARM virt guests) and
-   ``amd`` (:since:`since 11.5.0`).
+   (:since:`since 8.3.0`, for Q35 and ARM virt guests),
+   ``amd`` (:since:`since 11.5.0`), and ``smmuv3Dev`` (for
+   ARM virt guests).
+
+``parentIdx``
+   The ``parentIdx`` attribute notes the index of the controller that a
+   smmuv3Dev IOMMU device is attached to.
+
+``accel``
+   The ``accel`` attribute with possible values ``on`` and ``off`` can be used
+   to enable hardware acceleration support for smmuv3Dev IOMMU devices.
 
 ``driver``
    The ``driver`` subelement can be used to configure additional options, some
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 281846dfbe..42b2a5c74f 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -1353,6 +1353,7 @@ VIR_ENUM_IMPL(virDomainIOMMUModel,
               "smmuv3",
               "virtio",
               "amd",
+              "smmuv3Dev",
 );
 
 VIR_ENUM_IMPL(virDomainVsockModel,
@@ -2813,6 +2814,8 @@ virDomainIOMMUDefNew(void)
 
     iommu = g_new0(virDomainIOMMUDef, 1);
 
+    iommu->parent_idx = -1;
+
     return g_steal_pointer(&iommu);
 }
 
@@ -14407,6 +14410,14 @@ virDomainIOMMUDefParseXML(virDomainXMLOption *xmlopt,
                        VIR_XML_PROP_REQUIRED, &iommu->model) < 0)
         return NULL;
 
+    if (virXMLPropInt(node, "parentIdx", 10, VIR_XML_PROP_NONE,
+                      &iommu->parent_idx, -1) < 0)
+        return NULL;
+
+    if (virXMLPropTristateSwitch(node, "accel", VIR_XML_PROP_NONE,
+                               &iommu->accel) < 0)
+        return NULL;
+
     if ((driver = virXPathNode("./driver", ctxt))) {
         if (virXMLPropTristateSwitch(driver, "intremap", VIR_XML_PROP_NONE,
                                      &iommu->intremap) < 0)
@@ -22092,6 +22103,18 @@ virDomainIOMMUDefCheckABIStability(virDomainIOMMUDef *src,
                        dst->aw_bits, src->aw_bits);
         return false;
     }
+    if (src->parent_idx != dst->parent_idx) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("Target domain IOMMU device parent_idx value '%1$d' does not match source '%2$d'"),
+                       dst->parent_idx, src->parent_idx);
+        return false;
+    }
+    if (src->accel != dst->accel) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("Target domain IOMMU device accel value '%1$d' does not match source '%2$d'"),
+                       dst->accel, src->accel);
+        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'"),
@@ -28417,6 +28440,18 @@ virDomainIOMMUDefFormat(virBuffer *buf,
     virBufferAsprintf(&attrBuf, " model='%s'",
                       virDomainIOMMUModelTypeToString(iommu->model));
 
+    if (iommu->parent_idx >= 0 && iommu->model == VIR_DOMAIN_IOMMU_MODEL_SMMUV3_DEV) {
+        virBufferAsprintf(&attrBuf, " parentIdx='%d'",
+                          iommu->parent_idx);
+    }
+
+    if (iommu->model == VIR_DOMAIN_IOMMU_MODEL_SMMUV3_DEV) {
+        if (iommu->accel != VIR_TRISTATE_SWITCH_ABSENT) {
+            virBufferAsprintf(&attrBuf, " accel='%s'",
+                              virTristateSwitchTypeToString(iommu->accel));
+        }
+    }
+
     virXMLFormatElement(buf, "iommu", &attrBuf, &childBuf);
 }
 
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 39807b5fe3..c4541589d3 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -3039,6 +3039,7 @@ typedef enum {
     VIR_DOMAIN_IOMMU_MODEL_SMMUV3,
     VIR_DOMAIN_IOMMU_MODEL_VIRTIO,
     VIR_DOMAIN_IOMMU_MODEL_AMD,
+    VIR_DOMAIN_IOMMU_MODEL_SMMUV3_DEV,
 
     VIR_DOMAIN_IOMMU_MODEL_LAST
 } virDomainIOMMUModel;
@@ -3050,10 +3051,12 @@ struct _virDomainIOMMUDef {
     virTristateSwitch eim;
     virTristateSwitch iotlb;
     unsigned int aw_bits;
+    int parent_idx;
     virDomainDeviceInfo info;
     virTristateSwitch dma_translation;
     virTristateSwitch xtsup;
     virTristateSwitch pt;
+    virTristateSwitch accel;
 };
 
 typedef enum {
diff --git a/src/conf/domain_validate.c b/src/conf/domain_validate.c
index 93a2bc9b01..ba12ea706d 100644
--- a/src/conf/domain_validate.c
+++ b/src/conf/domain_validate.c
@@ -3108,7 +3108,8 @@ virDomainIOMMUDefValidate(const virDomainIOMMUDef *iommu)
             iommu->eim != VIR_TRISTATE_SWITCH_ABSENT ||
             iommu->iotlb != VIR_TRISTATE_SWITCH_ABSENT ||
             iommu->aw_bits != 0 ||
-            iommu->dma_translation != VIR_TRISTATE_SWITCH_ABSENT) {
+            iommu->dma_translation != VIR_TRISTATE_SWITCH_ABSENT ||
+            iommu->accel != VIR_TRISTATE_SWITCH_ABSENT) {
             virReportError(VIR_ERR_XML_ERROR,
                            _("iommu model '%1$s' doesn't support additional attributes"),
                            virDomainIOMMUModelTypeToString(iommu->model));
@@ -3120,7 +3121,8 @@ virDomainIOMMUDefValidate(const virDomainIOMMUDef *iommu)
         if (iommu->caching_mode != VIR_TRISTATE_SWITCH_ABSENT ||
             iommu->eim != VIR_TRISTATE_SWITCH_ABSENT ||
             iommu->aw_bits != 0 ||
-            iommu->dma_translation != VIR_TRISTATE_SWITCH_ABSENT) {
+            iommu->dma_translation != VIR_TRISTATE_SWITCH_ABSENT ||
+            iommu->accel != VIR_TRISTATE_SWITCH_ABSENT) {
             virReportError(VIR_ERR_XML_ERROR,
                            _("iommu model '%1$s' doesn't support some additional attributes"),
                            virDomainIOMMUModelTypeToString(iommu->model));
@@ -3130,7 +3132,24 @@ virDomainIOMMUDefValidate(const virDomainIOMMUDef *iommu)
 
     case VIR_DOMAIN_IOMMU_MODEL_INTEL:
         if (iommu->pt != VIR_TRISTATE_SWITCH_ABSENT ||
-            iommu->xtsup != VIR_TRISTATE_SWITCH_ABSENT) {
+            iommu->xtsup != VIR_TRISTATE_SWITCH_ABSENT ||
+            iommu->accel != VIR_TRISTATE_SWITCH_ABSENT) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("iommu model '%1$s' doesn't support some additional attributes"),
+                           virDomainIOMMUModelTypeToString(iommu->model));
+            return -1;
+        }
+        break;
+
+    case VIR_DOMAIN_IOMMU_MODEL_SMMUV3_DEV:
+        if (iommu->intremap != VIR_TRISTATE_SWITCH_ABSENT ||
+            iommu->caching_mode != VIR_TRISTATE_SWITCH_ABSENT ||
+            iommu->eim != VIR_TRISTATE_SWITCH_ABSENT ||
+            iommu->iotlb != VIR_TRISTATE_SWITCH_ABSENT ||
+            iommu->aw_bits != 0 ||
+            iommu->dma_translation != VIR_TRISTATE_SWITCH_ABSENT ||
+            iommu->xtsup != VIR_TRISTATE_SWITCH_ABSENT ||
+            iommu->pt != VIR_TRISTATE_SWITCH_ABSENT) {
             virReportError(VIR_ERR_XML_ERROR,
                            _("iommu model '%1$s' doesn't support some additional attributes"),
                            virDomainIOMMUModelTypeToString(iommu->model));
@@ -3155,6 +3174,7 @@ virDomainIOMMUDefValidate(const virDomainIOMMUDef *iommu)
 
     case VIR_DOMAIN_IOMMU_MODEL_VIRTIO:
     case VIR_DOMAIN_IOMMU_MODEL_AMD:
+    case VIR_DOMAIN_IOMMU_MODEL_SMMUV3_DEV:
     case VIR_DOMAIN_IOMMU_MODEL_LAST:
         break;
     }
diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/domaincommon.rng
index b9230a35b4..1aaa1a3180 100644
--- a/src/conf/schemas/domaincommon.rng
+++ b/src/conf/schemas/domaincommon.rng
@@ -6266,8 +6266,19 @@
           <value>smmuv3</value>
           <value>virtio</value>
           <value>amd</value>
+          <value>smmuv3Dev</value>
         </choice>
       </attribute>
+      <optional>
+        <attribute name="parentIdx">
+          <data type="unsignedInt"/>
+        </attribute>
+      </optional>
+      <optional>
+        <attribute name="accel">
+          <ref name="virOnOff"/>
+        </attribute>
+      </optional>
       <interleave>
         <optional>
           <element name="driver">
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 031f09b7a5..53088f8d8f 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -6294,6 +6294,63 @@ qemuBuildBootCommandLine(virCommand *cmd,
 }
 
 
+static virJSONValue *
+qemuBuildPCISmmuv3DevDevProps(const virDomainDef *def,
+                              const virDomainIOMMUDef *iommu)
+{
+    g_autoptr(virJSONValue) props = NULL;
+    g_autofree char *bus = NULL;
+    size_t i;
+    bool contIsPHB = false;
+
+    for (i = 0; i < def->ncontrollers; i++) {
+        virDomainControllerDef *cont = def->controllers[i];
+        if (cont->idx == iommu->parent_idx) {
+            if (cont->type == VIR_DOMAIN_CONTROLLER_TYPE_PCI) {
+                const char *alias = cont->info.alias;
+                contIsPHB = virDomainControllerIsPSeriesPHB(cont);
+
+                if (!alias)
+                    return NULL;
+
+                if (virDomainDeviceAliasIsUserAlias(alias)) {
+                    if (cont->model == VIR_DOMAIN_CONTROLLER_MODEL_PCI_ROOT &&
+                        iommu->parent_idx <= 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;
+            }
+        }
+    }
+
+    if (!bus)
+        return NULL;
+
+    if (contIsPHB && iommu->parent_idx > 0) {
+        char *temp_bus = g_strdup_printf("%s.0", bus);
+        g_free(bus);
+        bus = temp_bus;
+    }
+
+    if (virJSONValueObjectAdd(&props,
+                              "s:driver", "arm-smmuv3",
+                              "s:primary-bus", bus,
+                              "b:accel", (iommu->accel == VIR_TRISTATE_SWITCH_ON),
+                              NULL) < 0)
+        return NULL;
+
+    return g_steal_pointer(&props);
+}
+
+
 static int
 qemuBuildIOMMUCommandLine(virCommand *cmd,
                           const virDomainDef *def,
@@ -6342,7 +6399,6 @@ qemuBuildIOMMUCommandLine(virCommand *cmd,
         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:
@@ -6373,6 +6429,14 @@ qemuBuildIOMMUCommandLine(virCommand *cmd,
 
         return 0;
 
+    case VIR_DOMAIN_IOMMU_MODEL_SMMUV3_DEV:
+        if (!(props = qemuBuildPCISmmuv3DevDevProps(def, iommu)))
+            return -1;
+        if (qemuBuildDeviceCommandlineFromJSON(cmd, props, def, qemuCaps) < 0)
+            return -1;
+
+        return 0;
+
     case VIR_DOMAIN_IOMMU_MODEL_LAST:
     default:
         virReportEnumRangeError(virDomainIOMMUModel, iommu->model);
@@ -7206,6 +7270,7 @@ qemuBuildMachineCommandLine(virCommand *cmd,
         case VIR_DOMAIN_IOMMU_MODEL_INTEL:
         case VIR_DOMAIN_IOMMU_MODEL_VIRTIO:
         case VIR_DOMAIN_IOMMU_MODEL_AMD:
+        case VIR_DOMAIN_IOMMU_MODEL_SMMUV3_DEV:
             /* These IOMMUs are formatted in qemuBuildIOMMUCommandLine */
             break;
 
@@ -10860,15 +10925,15 @@ 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;
+
     if (qemuBuildMemoryDeviceCommandLine(cmd, cfg, def, priv) < 0)
         return NULL;
 
diff --git a/src/qemu/qemu_domain_address.c b/src/qemu/qemu_domain_address.c
index 96a9ca9b14..06bf4fab32 100644
--- a/src/qemu/qemu_domain_address.c
+++ b/src/qemu/qemu_domain_address.c
@@ -952,6 +952,7 @@ qemuDomainDeviceCalculatePCIConnectFlags(virDomainDeviceDef *dev,
 
             case VIR_DOMAIN_IOMMU_MODEL_INTEL:
             case VIR_DOMAIN_IOMMU_MODEL_SMMUV3:
+            case VIR_DOMAIN_IOMMU_MODEL_SMMUV3_DEV:
             case VIR_DOMAIN_IOMMU_MODEL_LAST:
                 /* These are not PCI devices */
                 return 0;
@@ -2378,6 +2379,7 @@ qemuDomainAssignDevicePCISlots(virDomainDef *def,
 
         case VIR_DOMAIN_IOMMU_MODEL_INTEL:
         case VIR_DOMAIN_IOMMU_MODEL_SMMUV3:
+        case VIR_DOMAIN_IOMMU_MODEL_SMMUV3_DEV:
         case VIR_DOMAIN_IOMMU_MODEL_LAST:
             /* These are not PCI devices */
             break;
diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
index c7ecb467a3..aac004c544 100644
--- a/src/qemu/qemu_validate.c
+++ b/src/qemu/qemu_validate.c
@@ -5414,6 +5414,22 @@ qemuValidateDomainDeviceDefIOMMU(const virDomainIOMMUDef *iommu,
         }
         break;
 
+    case VIR_DOMAIN_IOMMU_MODEL_SMMUV3_DEV:
+        if (!qemuDomainIsARMVirt(def)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("IOMMU device: '%1$s' is only supported with ARM Virt machines"),
+                           virDomainIOMMUModelTypeToString(iommu->model));
+            return -1;
+        }
+        // TODO: Check for pluggable device SMMUv3 qemu capability
+        if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_MACHINE_VIRT_IOMMU)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("IOMMU device: '%1$s' is not supported with this QEMU binary"),
+                           virDomainIOMMUModelTypeToString(iommu->model));
+            return -1;
+        }
+        break;
+
     case VIR_DOMAIN_IOMMU_MODEL_LAST:
     default:
         virReportEnumRangeError(virDomainIOMMUModel, iommu->model);
-- 
2.43.0

    