qemu: add a new video device model 'ramfb'

This device is a very simple framebuffer device supported by qemu that
is mostly intended to use as a boot framebuffer in conjunction with a
vgpu. However, there is also a standalone ramfb device that can be used
as a primary display device and is useful for e.g. aarch64 guests where
different memory mappings between the host and guest can prevent use of
other devices with framebuffers such as virtio-vga.

https://bugzilla.redhat.com/show_bug.cgi?id=1679680 describes the
issues in more detail.

Reviewed-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Jonathon Jongsma <jjongsma@redhat.com>

docs/formatdomain.html.in

@@ -7032,9 +7032,10 @@ qemu-kvm -net nic,model=? /dev/null
           "vbox", "qxl" (<span class="since">since 0.8.6</span>),
           "virtio" (<span class="since">since 1.3.0</span>),
           "gop" (<span class="since">since 3.2.0</span>),
-          "none" (<span class="since">since 4.6.0</span>, or "bochs"
+          "bochs" (<span class="since">since 5.6.0</span>), "ramfb"
-          (<span class="since">since 5.6.0</span>)
+          (<span class="since">since 5.9.0</span>), or "none"
-          depending on the hypervisor features available.
+          (<span class="since">since 4.6.0</span>,  depending on the hypervisor
+          features available.
           The purpose of the type <code>none</code> is to instruct libvirt not
           to add a default video device in the guest (see the paragraph above).
           This legacy behaviour can be inconvenient in cases where GPU mediated

docs/news.xml

@@ -41,6 +41,15 @@
 <libvirt>
   <release version="v5.9.0" date="unreleased">
     <section title="New features">
+      <change>
+        <summary>
+          qemu: Introduce a new video model of type 'ramfb'
+        </summary>
+        <description>
+          Introduce a new video model type to the domain XML that supports the
+          <code>ramfb</code> standalone device in qemu.
+        </description>
+      </change>
     </section>
     <section title="Improvements">
     </section>

docs/schemas/domaincommon.rng

@@ -3598,6 +3598,7 @@
                 <value>gop</value>
                 <value>none</value>
                 <value>bochs</value>
+                <value>ramfb</value>
               </choice>
             </attribute>
             <group>

src/conf/domain_conf.c

@@ -748,6 +748,7 @@ VIR_ENUM_IMPL(virDomainVideo,
               "gop",
               "none",
               "bochs",
+              "ramfb",
 );
 
 VIR_ENUM_IMPL(virDomainVideoVGAConf,
@@ -15299,6 +15300,7 @@ virDomainVideoDefaultRAM(const virDomainDef *def,
     case VIR_DOMAIN_VIDEO_TYPE_VIRTIO:
     case VIR_DOMAIN_VIDEO_TYPE_GOP:
     case VIR_DOMAIN_VIDEO_TYPE_NONE:
+    case VIR_DOMAIN_VIDEO_TYPE_RAMFB:
     case VIR_DOMAIN_VIDEO_TYPE_LAST:
     default:
         return 0;

src/conf/domain_conf.h

@@ -1399,6 +1399,7 @@ typedef enum {
     VIR_DOMAIN_VIDEO_TYPE_GOP,
     VIR_DOMAIN_VIDEO_TYPE_NONE,
     VIR_DOMAIN_VIDEO_TYPE_BOCHS,
+    VIR_DOMAIN_VIDEO_TYPE_RAMFB,
 
     VIR_DOMAIN_VIDEO_TYPE_LAST
 } virDomainVideoType;

src/qemu/qemu_command.c

@@ -114,6 +114,7 @@ VIR_ENUM_IMPL(qemuVideo,
               "" /* don't support gop */,
               "" /* 'none' doesn't make sense here */,
               "bochs-display",
+              "", /* ramfb can't be used with -vga */
 );
 
 VIR_ENUM_DECL(qemuDeviceVideo);
@@ -132,6 +133,7 @@ VIR_ENUM_IMPL(qemuDeviceVideo,
               "" /* don't support gop */,
               "" /* 'none' doesn't make sense here */,
               "bochs-display",
+              "ramfb",
 );
 
 VIR_ENUM_DECL(qemuDeviceVideoSecondary);
@@ -150,6 +152,7 @@ VIR_ENUM_IMPL(qemuDeviceVideoSecondary,
               "" /* don't support gop */,
               "" /* 'none' doesn't make sense here */,
               "" /* no secondary device for bochs */,
+              "" /* no secondary device for ramfb */,
 );
 
 VIR_ENUM_DECL(qemuSoundCodec);

src/qemu/qemu_domain.c

@@ -5725,6 +5725,7 @@ qemuDomainDeviceDefValidateVideo(const virDomainVideoDef *video)
     case VIR_DOMAIN_VIDEO_TYPE_QXL:
     case VIR_DOMAIN_VIDEO_TYPE_VIRTIO:
     case VIR_DOMAIN_VIDEO_TYPE_BOCHS:
+    case VIR_DOMAIN_VIDEO_TYPE_RAMFB:
     case VIR_DOMAIN_VIDEO_TYPE_LAST:
         break;
     }

src/qemu/qemu_domain_address.c

@@ -936,6 +936,7 @@ qemuDomainDeviceCalculatePCIConnectFlags(virDomainDeviceDefPtr dev,
         case VIR_DOMAIN_VIDEO_TYPE_DEFAULT:
         case VIR_DOMAIN_VIDEO_TYPE_GOP:
         case VIR_DOMAIN_VIDEO_TYPE_NONE:
+        case VIR_DOMAIN_VIDEO_TYPE_RAMFB:
         case VIR_DOMAIN_VIDEO_TYPE_LAST:
             return 0;
         }
@@ -1787,8 +1788,10 @@ qemuDomainValidateDevicePCISlotsPIIX3(virDomainDefPtr def,
             return -1;
     }
 
+    /* ramfb is not a PCI device */
     if (def->nvideos > 0 &&
-        def->videos[0]->type != VIR_DOMAIN_VIDEO_TYPE_NONE) {
+        def->videos[0]->type != VIR_DOMAIN_VIDEO_TYPE_NONE &&
+        def->videos[0]->type != VIR_DOMAIN_VIDEO_TYPE_RAMFB) {
         /* Because the PIIX3 integrated IDE/USB controllers are
          * already at slot 1, when qemu looks for the first free slot
          * to place the VGA controller (which is always the first
@@ -1971,8 +1974,10 @@ qemuDomainValidateDevicePCISlotsQ35(virDomainDefPtr def,
            return -1;
     }
 
+    /* ramfb is not a PCI device */
     if (def->nvideos > 0 &&
-        def->videos[0]->type != VIR_DOMAIN_VIDEO_TYPE_NONE) {
+        def->videos[0]->type != VIR_DOMAIN_VIDEO_TYPE_NONE &&
+        def->videos[0]->type != VIR_DOMAIN_VIDEO_TYPE_RAMFB) {
         /* NB: unlike the pc machinetypes, on q35 machinetypes the
          * integrated devices are at slot 0x1f, so when qemu looks for
          * the first free slot for the first VGA, it will always be at
@@ -2351,7 +2356,8 @@ qemuDomainAssignDevicePCISlots(virDomainDefPtr def,
 
     /* Video devices */
     for (i = 0; i < def->nvideos; i++) {
-        if (def->videos[i]->type == VIR_DOMAIN_VIDEO_TYPE_NONE)
+        if (def->videos[i]->type == VIR_DOMAIN_VIDEO_TYPE_NONE ||
+            def->videos[i]->type == VIR_DOMAIN_VIDEO_TYPE_RAMFB)
             continue;
 
         if (!virDeviceInfoPCIAddressIsWanted(&def->videos[i]->info))

src/qemu/qemu_process.c

@@ -5273,7 +5273,9 @@ qemuProcessStartValidateVideo(virDomainObjPtr vm,
                  video->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_CCW &&
                  !virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_VIRTIO_GPU_CCW)) ||
                 (video->type == VIR_DOMAIN_VIDEO_TYPE_BOCHS &&
-                !virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_BOCHS_DISPLAY))) {
+                !virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_BOCHS_DISPLAY)) ||
+                (video->type == VIR_DOMAIN_VIDEO_TYPE_RAMFB &&
+                 !virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_RAMFB))) {
                 virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                                _("this QEMU does not support '%s' video device"),
                                virDomainVideoTypeToString(video->type));

tests/qemuxml2argvdata/video-ramfb-display-device.x86_64-latest.args

@@ -0,0 +1,38 @@
+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-i686 \
+-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=tcg,usb=off,dump-guest-core=off \
+-m 1024 \
+-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 \
+-drive file=/var/lib/libvirt/images/QEMUGuest1,format=qcow2,if=none,\
+id=drive-ide0-0-0,cache=none \
+-device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1,\
+write-cache=on \
+-device ramfb,id=video0 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x2 \
+-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,\
+resourcecontrol=deny \
+-msg timestamp=on

tests/qemuxml2argvdata/video-ramfb-display-device.xml

@@ -0,0 +1,29 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>1048576</memory>
+  <currentMemory unit='KiB'>1048576</currentMemory>
+  <vcpu>1</vcpu>
+  <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>
+    <emulator>/usr/bin/qemu-system-i686</emulator>
+    <disk type='file' device='disk'>
+      <driver name='qemu' type='qcow2' cache='none'/>
+      <source file='/var/lib/libvirt/images/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='ide' index='0'/>
+    <video>
+      <model type='ramfb' />
+    </video>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -2083,6 +2083,7 @@ mymain(void)
             QEMU_CAPS_DEVICE_VIDEO_PRIMARY,
             QEMU_CAPS_VIRTIO_GPU_MAX_OUTPUTS);
     DO_TEST_CAPS_LATEST("video-bochs-display-device");
+    DO_TEST_CAPS_LATEST("video-ramfb-display-device");
     DO_TEST("video-none-device",
             QEMU_CAPS_VNC);
     DO_TEST_PARSE_ERROR("video-invalid-multiple-devices", NONE);