Implement a new iommufd attribute under hostdevs' PCI
subsystem driver that can be used to specify associated
iommufd object when launching a qemu VM.

Signed-off-by: Nathan Chen <nathanc@nvidia.com>
---
 docs/formatdomain.rst           |  8 ++++++++
 src/conf/device_conf.c          |  9 +++++++++
 src/conf/device_conf.h          |  1 +
 src/conf/schemas/basictypes.rng |  5 +++++
 src/qemu/qemu_command.c         | 19 +++++++++++++++++++
 5 files changed, 42 insertions(+)

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index 972493e62c..221bb22f3a 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -4836,6 +4836,7 @@ or:
    device; if PCI ROM loading is disabled through this attribute, attempts to
    tweak the loading process further using the ``bar`` or ``file`` attributes
    will be rejected. :since:`Since 4.3.0 (QEMU and KVM only)`.
+
 ``address``
    The ``address`` element for USB devices has a ``bus`` and ``device``
    attribute to specify the USB bus and device number the device appears at on
@@ -4876,6 +4877,13 @@ or:
    found is "problematic" in some way, the generic vfio-pci driver
    similarly be forced.
 
+   The ``<driver>`` element's ``iommufd`` attribute is used to specify
+   using the iommufd interface to propagate DMA mappings to the kernel,
+   instead of legacy VFIO. When the attribute is present, an iommufd
+   object will be created by the resulting qemu command. Libvirt will
+   open the /dev/iommu and VFIO device cdev, passing the associated
+   file descriptor numbers to the qemu command.
+
    (Note: :since:`Since 1.0.5`, the ``name`` attribute has been
    described to be used to select the type of PCI device assignment
    ("vfio", "kvm", or "xen"), but those values have been mostly
diff --git a/src/conf/device_conf.c b/src/conf/device_conf.c
index c278b81652..88979ecc39 100644
--- a/src/conf/device_conf.c
+++ b/src/conf/device_conf.c
@@ -60,6 +60,8 @@ int
 virDeviceHostdevPCIDriverInfoParseXML(xmlNodePtr node,
                                       virDeviceHostdevPCIDriverInfo *driver)
 {
+    virTristateBool iommufd;
+    driver->iommufd = false;
     if (virXMLPropEnum(node, "name",
                        virDeviceHostdevPCIDriverNameTypeFromString,
                        VIR_XML_PROP_NONZERO,
@@ -67,6 +69,10 @@ virDeviceHostdevPCIDriverInfoParseXML(xmlNodePtr node,
         return -1;
     }
 
+    if (virXMLPropTristateBool(node, "iommufd", VIR_XML_PROP_NONE, &iommufd) < 0)
+        return -1;
+    virTristateBoolToBool(iommufd, &driver->iommufd);
+
     driver->model = virXMLPropString(node, "model");
     return 0;
 }
@@ -93,6 +99,9 @@ virDeviceHostdevPCIDriverInfoFormat(virBuffer *buf,
 
     virBufferEscapeString(&driverAttrBuf, " model='%s'", driver->model);
 
+    if (driver->iommufd)
+        virBufferAddLit(&driverAttrBuf, " iommufd='yes'");
+
     virXMLFormatElement(buf, "driver", &driverAttrBuf, NULL);
     return 0;
 }
diff --git a/src/conf/device_conf.h b/src/conf/device_conf.h
index e570f51824..7bdbd80b0a 100644
--- a/src/conf/device_conf.h
+++ b/src/conf/device_conf.h
@@ -47,6 +47,7 @@ VIR_ENUM_DECL(virDeviceHostdevPCIDriverName);
 struct _virDeviceHostdevPCIDriverInfo {
     virDeviceHostdevPCIDriverName name;
     char *model;
+    bool iommufd;
 };
 
 typedef enum {
diff --git a/src/conf/schemas/basictypes.rng b/src/conf/schemas/basictypes.rng
index 2931e316b7..089fc0f1c2 100644
--- a/src/conf/schemas/basictypes.rng
+++ b/src/conf/schemas/basictypes.rng
@@ -673,6 +673,11 @@
           <ref name="genericName"/>
         </attribute>
       </optional>
+      <optional>
+        <attribute name="iommufd">
+          <ref name="virYesNo"/>
+        </attribute>
+      </optional>
       <empty/>
     </element>
   </define>
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 9f98a18695..38dab98dee 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -4808,6 +4808,7 @@ qemuBuildPCIHostdevDevProps(const virDomainDef *def,
     g_autofree char *host = virPCIDeviceAddressAsString(&pcisrc->addr);
     const char *failover_pair_id = NULL;
     const char *driver = NULL;
+    const char *iommufdId = NULL;
     /* 'ramfb' property must be omitted unless it's to be enabled */
     bool ramfb = pcisrc->ramfb == VIR_TRISTATE_SWITCH_ON;
 
@@ -4841,6 +4842,9 @@ qemuBuildPCIHostdevDevProps(const virDomainDef *def,
         teaming->persistent)
         failover_pair_id = teaming->persistent;
 
+    if (pcisrc->driver.iommufd)
+        iommufdId = "iommufd0";
+
     if (virJSONValueObjectAdd(&props,
                               "s:driver", driver,
                               "s:host", host,
@@ -4849,6 +4853,7 @@ qemuBuildPCIHostdevDevProps(const virDomainDef *def,
                               "S:failover_pair_id", failover_pair_id,
                               "S:display", qemuOnOffAuto(pcisrc->display),
                               "B:ramfb", ramfb,
+                              "S:iommufd", iommufdId,
                               NULL) < 0)
         return NULL;
 
@@ -5265,6 +5270,9 @@ qemuBuildHostdevCommandLine(virCommand *cmd,
                             virQEMUCaps *qemuCaps)
 {
     size_t i;
+    g_autoptr(virJSONValue) props = NULL;
+    int iommufd = 0;
+    const char * iommufdId = "iommufd0";
 
     for (i = 0; i < def->nhostdevs; i++) {
         virDomainHostdevDef *hostdev = def->hostdevs[i];
@@ -5293,6 +5301,17 @@ qemuBuildHostdevCommandLine(virCommand *cmd,
            if (hostdev->info->type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_UNASSIGNED)
                continue;
 
+            if (subsys->u.pci.driver.iommufd && iommufd == 0) {
+                iommufd = 1;
+                if (qemuMonitorCreateObjectProps(&props, "iommufd",
+                                                 iommufdId,
+                                                 NULL) < 0)
+                    return -1;
+
+                if (qemuBuildObjectCommandlineFromJSON(cmd, props) < 0)
+                    return -1;
+            }
+
             if (qemuCommandAddExtDevice(cmd, hostdev->info, def, qemuCaps) < 0)
                 return -1;
 
-- 
2.43.0