qemu: add 'ramfb' attribute for mediated devices

The 'ramfb' attribute provides a framebuffer to the guest that can be
used as a boot display for the vgpu

For example, the following configuration can be used to provide a vgpu
with a boot display:

    <hostdev mode='subsystem' type='mdev' model='vfio-pci' display='on' ramfb='on'>
        <source>
            <address uuid='$UUID'/>
        </source>
    </hostdev>

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

docs/formatdomain.html.in

@@ -4847,6 +4847,14 @@
           <a href="#elementsGraphics">graphical framebuffer</a> in order to
           use this attribute, currently only supported with VNC, Spice and
           egl-headless graphics devices.
+
+          <span class="since">Since version 5.10.0</span>, there is an optional
+          <code>ramfb</code> attribute for devices with
+          <code>model='vfio-pci'</code>. Supported values are either
+          <code>on</code> or <code>off</code> (default is 'off').  When
+          enabled, this attribute provides a memory framebuffer device to the
+          guest.  This framebuffer will be used as a boot display when a vgpu
+          device is the primary display.
           <p>
             Note: There are also some implications on the usage of guest's
             address type depending on the <code>model</code> attribute,

docs/schemas/domaincommon.rng

@@ -4779,6 +4779,11 @@
         <value>vfio-ap</value>
       </choice>
     </attribute>
+    <optional>
+      <attribute name="ramfb">
+        <ref name="virOnOff"/>
+      </attribute>
+    </optional>
     <optional>
       <attribute name="display">
         <ref name="virOnOff"/>

src/conf/domain_conf.c

@@ -8135,6 +8135,7 @@ virDomainHostdevDefParseXMLSubsys(xmlNodePtr node,
     g_autofree char *backendStr = NULL;
     g_autofree char *model = NULL;
     g_autofree char *display = NULL;
+    g_autofree char *ramfb = NULL;
 
     /* @managed can be read from the xml document - it is always an
      * attribute of the toplevel element, no matter what type of
@@ -8148,6 +8149,7 @@ virDomainHostdevDefParseXMLSubsys(xmlNodePtr node,
     rawio = virXMLPropString(node, "rawio");
     model = virXMLPropString(node, "model");
     display = virXMLPropString(node, "display");
+    ramfb = virXMLPropString(node, "ramfb");
 
     /* @type is passed in from the caller rather than read from the
      * xml document, because it is specified in different places for
@@ -8256,6 +8258,15 @@ virDomainHostdevDefParseXMLSubsys(xmlNodePtr node,
                            display);
             return -1;
         }
+
+        if (ramfb &&
+            (mdevsrc->ramfb = virTristateSwitchTypeFromString(ramfb)) <= 0) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("unknown value '%s' for <hostdev> attribute "
+                             "'ramfb'"),
+                           ramfb);
+            return -1;
+        }
     }
 
     switch (def->source.subsys.type) {

src/conf/domain_conf.h

@@ -262,6 +262,7 @@ struct _virDomainHostdevSubsysMediatedDev {
     int model;                          /* enum virMediatedDeviceModelType */
     int display; /* virTristateSwitch */
     char uuidstr[VIR_UUID_STRING_BUFLEN];   /* mediated device's uuid string */
+    int ramfb; /* virTristateSwitch */
 };
 
 typedef enum {

src/qemu/qemu_command.c

@@ -5329,6 +5329,19 @@ qemuBuildChrChardevStr(virLogManagerPtr logManager,
 }
 
 
+static const char *
+qemuBuildHostdevMdevModelTypeString(virDomainHostdevSubsysMediatedDevPtr mdev)
+{
+    /* when the 'ramfb' attribute is set, we must use the nohotplug variant
+     * rather than 'vfio-pci' */
+    if (mdev->model == VIR_MDEV_MODEL_TYPE_VFIO_PCI &&
+        mdev->ramfb == VIR_TRISTATE_SWITCH_ON)
+        return "vfio-pci-nohotplug";
+
+    return virMediatedDeviceModelTypeToString(mdev->model);
+}
+
+
 char *
 qemuBuildHostdevMediatedDevStr(const virDomainDef *def,
                                virDomainHostdevDefPtr dev,
@@ -5342,7 +5355,7 @@ qemuBuildHostdevMediatedDevStr(const virDomainDef *def,
     if (!(mdevPath = virMediatedDeviceGetSysfsPath(mdevsrc->uuidstr)))
         return NULL;
 
-    dev_str = virMediatedDeviceModelTypeToString(mdevsrc->model);
+    dev_str = qemuBuildHostdevMdevModelTypeString(mdevsrc);
 
     if (!dev_str)
         return NULL;
@@ -5360,6 +5373,10 @@ qemuBuildHostdevMediatedDevStr(const virDomainDef *def,
     if (dev->info->bootIndex)
         virBufferAsprintf(&buf, ",bootindex=%u", dev->info->bootIndex);
 
+    if (mdevsrc->ramfb == VIR_TRISTATE_SWITCH_ON)
+        virBufferAsprintf(&buf, ",ramfb=%s",
+                          virTristateSwitchTypeToString(mdevsrc->ramfb));
+
     return virBufferContentAndReset(&buf);
 }
 

tests/qemuxml2argvdata/hostdev-mdev-display-ramfb.x86_64-latest.args

@@ -0,0 +1,37 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/tmp/lib/domain--1-QEMUGuest2 \
+USER=test \
+LOGNAME=test \
+XDG_DATA_HOME=/tmp/lib/domain--1-QEMUGuest2/.local/share \
+XDG_CACHE_HOME=/tmp/lib/domain--1-QEMUGuest2/.cache \
+XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest2/.config \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-i686 \
+-name guest=QEMUGuest2,debug-threads=on \
+-S \
+-object secret,id=masterKey0,format=raw,\
+file=/tmp/lib/domain--1-QEMUGuest2/master-key.aes \
+-machine pc,accel=tcg,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 \
+-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 \
+-vnc 127.0.0.1:0 \
+-device qxl-vga,id=video0,ram_size=67108864,vram_size=67108864,\
+vram64_size_mb=0,vgamem_mb=16,max_outputs=1,bus=pci.0,addr=0x2 \
+-device vfio-pci-nohotplug,id=hostdev0,\
+sysfsdev=/sys/bus/mdev/devices/53764d0e-85a0-42b4-af5c-2046b460b1dc,display=on,\
+bus=pci.0,addr=0x3,ramfb=on \
+-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,\
+resourcecontrol=deny \
+-msg timestamp=on

tests/qemuxml2argvdata/hostdev-mdev-display-ramfb.xml

@@ -0,0 +1,33 @@
+<domain type='qemu'>
+  <name>QEMUGuest2</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>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>
+    <controller type='usb' index='0'>
+    </controller>
+    <controller type='pci' index='0' model='pci-root'/>
+    <controller type='ide' index='0'>
+    </controller>
+    <graphics type='vnc'/>
+    <hostdev mode='subsystem' type='mdev' model='vfio-pci' display='on' ramfb='on'>
+      <source>
+        <address uuid='53764d0e-85a0-42b4-af5c-2046b460b1dc'/>
+      </source>
+    </hostdev>
+    <video>
+      <model type='qxl' heads='1'/>
+    </video>
+    <memballoon model='none'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -1605,6 +1605,7 @@ mymain(void)
     DO_TEST_PARSE_ERROR("hostdev-mdev-display-missing-graphics",
             QEMU_CAPS_DEVICE_VFIO_PCI,
             QEMU_CAPS_VFIO_PCI_DISPLAY);
+    DO_TEST_CAPS_LATEST("hostdev-mdev-display-ramfb");
     DO_TEST_PARSE_ERROR("hostdev-vfio-zpci-wrong-arch",
                         QEMU_CAPS_DEVICE_VFIO_PCI);
     DO_TEST("hostdev-vfio-zpci",