qemu: reject readonly attribute for virtiofs

This is not yet supported by virtiofsd.

Fixes #23 a.k.a. https://gitlab.com/libvirt/libvirt/-/issues/23

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>

src/qemu/qemu_validate.c

@@ -3418,6 +3418,11 @@ qemuValidateDomainDeviceDefFS(virDomainFSDefPtr fs,
         return -1;
 
     case VIR_DOMAIN_FS_DRIVER_TYPE_VIRTIOFS:
+        if (fs->readonly) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("virtiofs does not yet support read-only mode"));
+            return -1;
+        }
         if (!driver->privileged) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                            _("virtiofs is not yet supported in session mode"));

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

@@ -0,0 +1,44 @@
+<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' accessmode='passthrough'>
+      <driver type='virtiofs' queue='1024'/>
+      <binary path='/usr/libexec/virtiofsd' xattr='on'>
+        <cache mode='always'/>
+        <lock posix='off' flock='off'/>
+      </binary>
+      <source dir='/path'/>
+      <target dir='mount_tag'/>
+      <readonly/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
+    </filesystem>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='none'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -3171,6 +3171,7 @@ mymain(void)
 
     DO_TEST_CAPS_LATEST("vhost-user-fs-fd-memory");
     DO_TEST_CAPS_LATEST("vhost-user-fs-hugepages");
+    DO_TEST_CAPS_LATEST_PARSE_ERROR("vhost-user-fs-readonly");
 
     DO_TEST("riscv64-virt",
             QEMU_CAPS_DEVICE_VIRTIO_MMIO);