From fdb3a965d8cea1b1fcaf91504d1e5447ae7b6358 Mon Sep 17 00:00:00 2001
Message-ID: <fdb3a965d8cea1b1fcaf91504d1e5447ae7b6358.1774618368.git.jdenemar@redhat.com>
From: Pavel Hrdina <phrdina@redhat.com>
Date: Fri, 13 Mar 2026 11:57:57 +0100
Subject: [PATCH] conf: Introduce domain iommufd element

In addition to configuring IOMMUFD for each host device add
configuration for the whole VM. This will be extended to add support for
passing FD to libvirt from management applications.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
(cherry picked from commit c03b8f0804f648a2bbc2eb7e957f2f8821b8e167)

Resolves: https://redhat.atlassian.net/browse/RHEL-159175
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
---
 docs/formatdomain.rst                  | 21 ++++++++++++
 src/conf/domain_conf.c                 | 46 ++++++++++++++++++++++++++
 src/conf/domain_conf.h                 |  2 ++
 src/conf/schemas/domaincommon.rng      | 12 +++++++
 tests/genericxml2xmlindata/iommufd.xml | 18 ++++++++++
 tests/genericxml2xmltest.c             |  2 ++
 6 files changed, 101 insertions(+)
 create mode 100644 tests/genericxml2xmlindata/iommufd.xml

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index ff07f2fc17..20ea10bd35 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -1382,6 +1382,27 @@ Block I/O Tuning
    ``write_iops_sec``
       Write I/O operations per second limit. :since:`Since 1.2.2`
 
+Host Device IOMMUFD
+-------------------
+
+::
+
+   <domain>
+     ...
+     <iommufd enabled='yes'/>
+     ...
+   </domain>
+
+``iommufd``
+   :since:`Since 12.2.0 (QEMU/KVM only)` The optional ``iommufd`` element with
+   mandatory ``enabled`` attribute can be used to enable IOMMUFD backend for
+   VFIO host devices. This provides an interface to propagate DMA mappings to
+   kernel for assigned devices. Libvirt will open the /dev/iommu and VFIO device
+   cdev and pass associated file descriptors to QEMU.
+
+   This controls IOMMUFD usage for all host devices, each device can change this
+   global default by setting ``iommufd`` attribute for ``driver`` element.
+
 Resource partitioning
 ---------------------
 
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index d029fc01ea..59908d9da6 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -19773,6 +19773,31 @@ virDomainDefControllersParse(virDomainDef *def,
     return 0;
 }
 
+static int
+virDomainDefIommufdParse(virDomainDef *def,
+                         xmlXPathContextPtr ctxt)
+{
+    int n;
+    g_autofree xmlNodePtr *nodes = NULL;
+
+    if ((n = virXPathNodeSet("./iommufd", ctxt, &nodes)) < 0)
+        return -1;
+
+    if (n > 1) {
+        virReportError(VIR_ERR_XML_ERROR, "%s",
+                       _("only one 'iommufd' element is supported"));
+        return -1;
+    }
+
+    if (n == 0)
+        return 0;
+
+    if (virXMLPropTristateBool(nodes[0], "enabled", VIR_XML_PROP_REQUIRED, &def->iommufd) < 0)
+        return -1;
+
+    return 0;
+}
+
 static virDomainDef *
 virDomainDefParseXML(xmlXPathContextPtr ctxt,
                      virDomainXMLOption *xmlopt,
@@ -19851,6 +19876,9 @@ virDomainDefParseXML(xmlXPathContextPtr ctxt,
         !virDomainIOThreadIDArrayHasPin(def))
         def->placement_mode = VIR_DOMAIN_CPU_PLACEMENT_MODE_AUTO;
 
+    if (virDomainDefIommufdParse(def, ctxt) < 0)
+        return NULL;
+
     if ((n = virXPathNodeSet("./resource", ctxt, &nodes)) < 0)
         return NULL;
 
@@ -27988,6 +28016,22 @@ virDomainHubDefFormat(virBuffer *buf,
 }
 
 
+static void
+virDomainDefIommufdFormat(virBuffer *buf,
+                          virDomainDef *def)
+{
+    g_auto(virBuffer) attrBuf = VIR_BUFFER_INITIALIZER;
+
+    if (def->iommufd == VIR_TRISTATE_BOOL_ABSENT)
+        return;
+
+    virBufferAsprintf(&attrBuf, " enabled='%s'",
+                      virTristateBoolTypeToString(def->iommufd));
+
+    virXMLFormatElement(buf, "iommufd", &attrBuf, NULL);
+}
+
+
 static void
 virDomainResourceDefFormat(virBuffer *buf,
                            virDomainResourceDef *def)
@@ -29526,6 +29570,8 @@ virDomainDefFormatInternalSetRootName(virDomainDef *def,
     if (virDomainNumatuneFormatXML(buf, def->numa) < 0)
         return -1;
 
+    virDomainDefIommufdFormat(buf, def);
+
     virDomainResourceDefFormat(buf, def->resource);
 
     for (i = 0; i < def->nsysinfo; i++) {
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index a1cc2f05ac..145084e4fd 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -3240,6 +3240,8 @@ struct _virDomainDef {
     virTristateSwitch apic_eoi;
     virDomainFeatureTCG *tcg_features;
 
+    virTristateBool iommufd;
+
     bool tseg_specified;
     unsigned long long tseg_size;
 
diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/domaincommon.rng
index fa7220deae..de505e6c49 100644
--- a/src/conf/schemas/domaincommon.rng
+++ b/src/conf/schemas/domaincommon.rng
@@ -1025,6 +1025,10 @@
         <ref name="numatune"/>
       </optional>
 
+      <optional>
+        <ref name="iommufd"/>
+      </optional>
+
       <optional>
         <ref name="respartition"/>
       </optional>
@@ -1368,6 +1372,14 @@
     </element>
   </define>
 
+  <define name="iommufd">
+    <element name="iommufd">
+      <attribute name="enabled">
+        <ref name="virYesNo"/>
+      </attribute>
+    </element>
+  </define>
+
   <define name="respartition">
     <element name="resource">
       <optional>
diff --git a/tests/genericxml2xmlindata/iommufd.xml b/tests/genericxml2xmlindata/iommufd.xml
new file mode 100644
index 0000000000..63ea839383
--- /dev/null
+++ b/tests/genericxml2xmlindata/iommufd.xml
@@ -0,0 +1,18 @@
+<domain type='kvm'>
+  <name>foo</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <iommufd enabled='yes'/>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+  </devices>
+</domain>
diff --git a/tests/genericxml2xmltest.c b/tests/genericxml2xmltest.c
index 6757fc44de..6be694cac5 100644
--- a/tests/genericxml2xmltest.c
+++ b/tests/genericxml2xmltest.c
@@ -263,6 +263,8 @@ mymain(void)
 
     DO_TEST("iothreadids");
 
+    DO_TEST("iommufd");
+
     virObjectUnref(caps);
     virObjectUnref(xmlopt);
 
-- 
2.53.0