qemu: Implement builtin rng backend

Since v4.2-rc0, QEMU introduced a builtin rng backend that uses
getrandom() syscall to generate random. Add it to libvirt with the
backend model 'builtin'.

https://bugzilla.redhat.com/show_bug.cgi?id=1785091Signed-off-by: NHan Han <hhan@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_capabilities.c

@@ -5844,6 +5844,8 @@ virQEMUCapsFillDomainDeviceRNGCaps(virQEMUCapsPtr qemuCaps,
         VIR_DOMAIN_CAPS_ENUM_SET(rng->backendModel, VIR_DOMAIN_RNG_BACKEND_EGD);
     if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_RNG_RANDOM))
         VIR_DOMAIN_CAPS_ENUM_SET(rng->backendModel, VIR_DOMAIN_RNG_BACKEND_RANDOM);
+    if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_RNG_BUILTIN))
+        VIR_DOMAIN_CAPS_ENUM_SET(rng->backendModel, VIR_DOMAIN_RNG_BACKEND_BUILTIN);
 }
 
 

src/qemu/qemu_command.c

@@ -5583,6 +5583,7 @@ qemuBuildRNGBackendChrdevStr(virLogManagerPtr logManager,
 
     switch ((virDomainRNGBackend) rng->backend) {
     case VIR_DOMAIN_RNG_BACKEND_RANDOM:
+    case VIR_DOMAIN_RNG_BACKEND_BUILTIN:
     case VIR_DOMAIN_RNG_BACKEND_LAST:
         /* no chardev backend is needed */
         return 0;
@@ -5595,11 +5596,6 @@ qemuBuildRNGBackendChrdevStr(virLogManagerPtr logManager,
                                             cdevflags)))
             return -1;
         break;
-
-    case VIR_DOMAIN_RNG_BACKEND_BUILTIN:
-        virReportUnsupportedError();
-        return -1;
-        break;
     }
 
     return 0;
@@ -5651,8 +5647,18 @@ qemuBuildRNGBackendProps(virDomainRNGDefPtr rng,
         break;
 
     case VIR_DOMAIN_RNG_BACKEND_BUILTIN:
-        virReportUnsupportedError();
-        return -1;
+        if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_RNG_BUILTIN)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("this qemu doesn't support the rng-builtin "
+                             "backend"));
+            return -1;
+        }
+
+        if (qemuMonitorCreateObjectProps(props, "rng-builtin", objAlias,
+                                         NULL) < 0)
+            return -1;
+
+        break;
 
     case VIR_DOMAIN_RNG_BACKEND_LAST:
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",

tests/domaincapsdata/qemu_4.2.0-q35.x86_64.xml

@@ -167,6 +167,7 @@
       <enum name='backendModel'>
         <value>random</value>
         <value>egd</value>
+        <value>builtin</value>
       </enum>
     </rng>
   </devices>

tests/domaincapsdata/qemu_4.2.0-tcg.x86_64.xml

@@ -178,6 +178,7 @@
       <enum name='backendModel'>
         <value>random</value>
         <value>egd</value>
+        <value>builtin</value>
       </enum>
     </rng>
   </devices>

tests/domaincapsdata/qemu_4.2.0-virt.aarch64.xml

@@ -136,6 +136,7 @@
       <enum name='backendModel'>
         <value>random</value>
         <value>egd</value>
+        <value>builtin</value>
       </enum>
     </rng>
   </devices>

tests/domaincapsdata/qemu_4.2.0.aarch64.xml

@@ -134,6 +134,7 @@
       <enum name='backendModel'>
         <value>random</value>
         <value>egd</value>
+        <value>builtin</value>
       </enum>
     </rng>
   </devices>

tests/domaincapsdata/qemu_4.2.0.ppc64.xml

@@ -100,6 +100,7 @@
       <enum name='backendModel'>
         <value>random</value>
         <value>egd</value>
+        <value>builtin</value>
       </enum>
     </rng>
   </devices>

tests/domaincapsdata/qemu_4.2.0.s390x.xml

@@ -190,6 +190,7 @@
       <enum name='backendModel'>
         <value>random</value>
         <value>egd</value>
+        <value>builtin</value>
       </enum>
     </rng>
   </devices>

tests/domaincapsdata/qemu_4.2.0.x86_64.xml

@@ -167,6 +167,7 @@
       <enum name='backendModel'>
         <value>random</value>
         <value>egd</value>
+        <value>builtin</value>
       </enum>
     </rng>
   </devices>

tests/qemuxml2argvdata/virtio-rng-builtin.x86_64-latest.args

+LC_ALL=C \
+PATH=/bin \
+HOME=/tmp/lib/domain--1-QEMUGuest1 \
+USER=test \
+LOGNAME=test \
+XDG_DATA_HOME=/tmp/lib/domain--1-QEMUGuest1/.local/share \
+XDG_CACHE_HOME=/tmp/lib/domain--1-QEMUGuest1/.cache \
+XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name guest=QEMUGuest1,debug-threads=on \
+-S \
+-object secret,id=masterKey0,format=raw,\
+file=/tmp/lib/domain--1-QEMUGuest1/master-key.aes \
+-machine pc,accel=kvm,usb=off,dump-guest-core=off \
+-m 214 \
+-overcommit mem-lock=off \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-display none \
+-no-user-config \
+-nodefaults \
+-chardev socket,id=charmonitor,fd=1729,server,nowait \
+-mon chardev=charmonitor,id=monitor,mode=control \
+-rtc base=utc \
+-no-shutdown \
+-no-acpi \
+-boot strict=on \
+-device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x2 \
+-object rng-builtin,id=objrng0 \
+-device virtio-rng-pci,rng=objrng0,id=rng0,bus=pci.0,addr=0x3 \
+-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,\
+resourcecontrol=deny \
+-msg timestamp=on

tests/qemuxml2argvdata/virtio-rng-builtin.xml

+<domain type='kvm'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu>1</vcpu>
+  <os>
+    <type arch='x86_64' 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>
+    <emulator>/usr/bin/qemu-system-x86_64</emulator>
+    <controller type='usb' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='virtio'/>
+    <rng model='virtio'>
+      <backend model='builtin'/>
+    </rng>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -2121,6 +2121,7 @@ mymain(void)
     DO_TEST("virtio-rng-egd",
             QEMU_CAPS_DEVICE_VIRTIO_RNG,
             QEMU_CAPS_OBJECT_RNG_EGD);
+    DO_TEST_CAPS_LATEST("virtio-rng-builtin");
     DO_TEST_CAPS_VER("virtio-rng-egd-unix", "2.5.0");
     DO_TEST_CAPS_LATEST("virtio-rng-egd-unix");
     DO_TEST("virtio-rng-multiple",

tests/qemuxml2xmloutdata/virtio-rng-builtin.x86_64-latest.xml

+<domain type='kvm'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' 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>
+    <emulator>/usr/bin/qemu-system-x86_64</emulator>
+    <controller type='usb' index='0' model='piix3-uhci'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
+    </controller>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='virtio'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
+    </memballoon>
+    <rng model='virtio'>
+      <backend model='builtin'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
+    </rng>
+  </devices>
+</domain>

tests/qemuxml2xmltest.c

@@ -630,6 +630,7 @@ mymain(void)
             QEMU_CAPS_DEVICE_VIRTIO_RNG);
     DO_TEST("virtio-rng-egd",
             QEMU_CAPS_DEVICE_VIRTIO_RNG);
+    DO_TEST_CAPS_LATEST("virtio-rng-builtin");
 
     DO_TEST("pseries-nvram",
             QEMU_CAPS_DEVICE_SPAPR_PCI_HOST_BRIDGE,