conf: add socket for virtiofs filesystems

Allow passing a socket of an externally launched virtiofsd
to the vhost-user-fs device.

<filesystem type='mount'>
  <driver type='virtiofs' queue='1024'/>
  <source socket='/tmp/sock/'/>
</filesystem>

https://bugzilla.redhat.com/show_bug.cgi?id=1855789

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

docs/schemas/domaincommon.rng

@@ -2763,9 +2763,18 @@
                 <ref name="fsBinary"/>
               </optional>
               <element name="source">
+              <choice>
+              <group>
                 <attribute name="dir">
                   <ref name="absDirPath"/>
                 </attribute>
+              </group>
+              <group>
+              <attribute name="socket">
+                <ref name="absFilePath"/>
+              </attribute>
+              </group>
+              </choice>
                 <empty/>
               </element>
             </interleave>
@@ -2827,10 +2836,12 @@
           </group>
         </choice>
         <interleave>
+          <optional>
           <element name="target">
             <attribute name="dir"/>
             <empty/>
           </element>
+          </optional>
           <optional>
             <attribute name="accessmode">
               <choice>

src/conf/domain_conf.c

@@ -2480,6 +2480,7 @@ void virDomainFSDefFree(virDomainFSDef *def)
     g_free(def->virtio);
     virObjectUnref(def->privateData);
     g_free(def->binary);
+    g_free(def->sock);
 
     g_free(def);
 }
@@ -5516,7 +5517,7 @@ virDomainMemoryDefPostParse(virDomainMemoryDef *mem,
 static int
 virDomainFSDefPostParse(virDomainFSDef *fs)
 {
-    if (fs->accessmode == VIR_DOMAIN_FS_ACCESSMODE_DEFAULT)
+    if (fs->accessmode == VIR_DOMAIN_FS_ACCESSMODE_DEFAULT && !fs->sock)
         fs->accessmode = VIR_DOMAIN_FS_ACCESSMODE_PASSTHROUGH;
 
     return 0;
@@ -10031,6 +10032,7 @@ virDomainFSDefParseXML(virDomainXMLOption *xmlopt,
     g_autofree char *multidevs = NULL;
     g_autofree char *fmode = NULL;
     g_autofree char *dmode = NULL;
+    g_autofree char *sock = NULL;
 
     ctxt->node = node;
 
@@ -10113,9 +10115,9 @@ virDomainFSDefParseXML(virDomainXMLOption *xmlopt,
     cur = node->children;
     while (cur != NULL) {
         if (cur->type == XML_ELEMENT_NODE) {
-            if (!source &&
+            if (!source && !sock &&
                 virXMLNodeNameEqual(cur, "source")) {
-
+                sock = virXMLPropString(cur, "socket");
                 if (def->type == VIR_DOMAIN_FS_TYPE_MOUNT ||
                     def->type == VIR_DOMAIN_FS_TYPE_BIND) {
                     source = virXMLPropString(cur, "dir");
@@ -10237,13 +10239,13 @@ virDomainFSDefParseXML(virDomainXMLOption *xmlopt,
     }
 
     if (source == NULL && def->type != VIR_DOMAIN_FS_TYPE_RAM
-        && def->type != VIR_DOMAIN_FS_TYPE_VOLUME) {
+        && def->type != VIR_DOMAIN_FS_TYPE_VOLUME && !sock) {
         virReportError(VIR_ERR_NO_SOURCE,
                        target ? "%s" : NULL, target);
         goto error;
     }
 
-    if (target == NULL) {
+    if (target == NULL && !sock) {
         virReportError(VIR_ERR_NO_TARGET,
                        source ? "%s" : NULL, source);
         goto error;
@@ -10267,6 +10269,7 @@ virDomainFSDefParseXML(virDomainXMLOption *xmlopt,
     }
 
     def->src->path = g_steal_pointer(&source);
+    def->sock = g_steal_pointer(&sock);
     def->dst = g_steal_pointer(&target);
 
     if (virDomainDeviceInfoParseXML(xmlopt, node, ctxt, &def->info,
@@ -22199,7 +22202,7 @@ static bool
 virDomainFsDefCheckABIStability(virDomainFSDef *src,
                                 virDomainFSDef *dst)
 {
-    if (STRNEQ(src->dst, dst->dst)) {
+    if (STRNEQ_NULLABLE(src->dst, dst->dst)) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                        _("Target filesystem guest target %s does not match source %s"),
                        dst->dst, src->dst);
@@ -25337,8 +25340,10 @@ virDomainFSDefFormat(virBuffer *buf,
     switch (def->type) {
     case VIR_DOMAIN_FS_TYPE_MOUNT:
     case VIR_DOMAIN_FS_TYPE_BIND:
-        virBufferEscapeString(buf, "<source dir='%s'/>\n",
+        if (!def->sock)
-                              src);
+            virBufferEscapeString(buf, "<source dir='%s'/>\n", src);
+        else
+            virBufferEscapeString(buf, "<source socket='%s'/>\n", def->sock);
         break;
 
     case VIR_DOMAIN_FS_TYPE_BLOCK:

src/conf/domain_conf.h

@@ -861,6 +861,7 @@ struct _virDomainFSDef {
     int multidevs; /* virDomainFSMultidevs */
     unsigned long long usage; /* in bytes */
     virStorageSource *src;
+    char *sock;
     char *dst;
     bool readonly;
     virDomainDeviceInfo info;

src/qemu/qemu_validate.c

@@ -4162,6 +4162,7 @@ qemuValidateDomainDeviceDefFS(virDomainFSDef *fs,
         return -1;
 
     case VIR_DOMAIN_FS_DRIVER_TYPE_VIRTIOFS:
+        if (!fs->sock) {
             if (fs->readonly) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                            _("virtiofs does not yet support read-only mode"));
@@ -4182,6 +4183,8 @@ qemuValidateDomainDeviceDefFS(virDomainFSDef *fs,
                            _("virtiofs does not support wrpolicy"));
             return -1;
             }
+        }
+
         if (fs->model != VIR_DOMAIN_FS_MODEL_DEFAULT) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                            _("virtiofs does not support model"));

tests/qemuxml2argvdata/vhost-user-fs-sock.xml

@@ -0,0 +1,39 @@
+<domain type='kvm'>
+  <name>guest</name>
+  <uuid>126f2720-6f8e-45ab-a886-ec9277079a67</uuid>
+  <memory unit='KiB'>14680064</memory>
+  <currentMemory unit='KiB'>14680064</currentMemory>
+  <memoryBacking>
+    <source type='file'/>
+    <access mode='shared'/>
+  </memoryBacking>
+  <vcpu placement='static'>2</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu mode='custom' match='exact' check='none'>
+    <model fallback='forbid'>qemu64</model>
+    <numa>
+      <cell id='0' cpus='0-1' memory='14680064' unit='KiB' memAccess='shared'/>
+    </numa>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu-system-x86_64</emulator>
+    <controller type='usb' index='0' model='none'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <filesystem type='mount'>
+      <driver type='virtiofs' queue='1024'/>
+      <source socket='/tmp/sock'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
+    </filesystem>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <audio id='1' type='none'/>
+    <memballoon model='none'/>
+  </devices>
+</domain>

tests/qemuxml2xmloutdata/vhost-user-fs-sock.x86_64-latest.xml

@@ -0,0 +1 @@
+../qemuxml2argvdata/vhost-user-fs-sock.xml

tests/qemuxml2xmltest.c

@@ -1434,6 +1434,7 @@ mymain(void)
 
     DO_TEST_CAPS_LATEST("vhost-user-fs-fd-memory");
     DO_TEST_CAPS_LATEST("vhost-user-fs-hugepages");
+    DO_TEST_CAPS_LATEST("vhost-user-fs-sock");
 
     DO_TEST("riscv64-virt",
             QEMU_CAPS_DEVICE_VIRTIO_MMIO);