libxl: Implement basic video device selection

This started as an investigation into an issue where libvirt (using the
libxl driver) and the Xen host, like an old couple, could not agree on
who is responsible for selecting the VNC port to use.

Things usually (and a bit surprisingly) did work because, just like that
old couple, they had the same idea on what to do by default. However it
was possible that this ended up in a big argument.

The problem is that display information exists in two different places:
in the vfbs list and in the build info. And for launching the device model,
only the latter is used. But that never gets initialized from libvirt. So
Xen allows the device model to select a default port while libvirt thinks
it has told Xen that this is done by libvirt (though the vfbs config).

While fixing that, I made a stab at actually evaluating the configuration
of the video device. So that it is now possible to at least decide between
a Cirrus or standard VGA emulation and to modify the VRAM within certain
limits using libvirt.

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Jim Fehlig <jfehlig@suse.com>

src/libxl/libxl_conf.c

@@ -1433,6 +1433,72 @@ libxlMakePCIList(virDomainDefPtr def, libxl_domain_config *d_config)
     return -1;
 }
 
+static int
+libxlMakeVideo(virDomainDefPtr def, libxl_domain_config *d_config)
+
+{
+    libxl_domain_build_info *b_info = &d_config->b_info;
+    int dm_type = libxlDomainGetEmulatorType(def);
+
+    if (d_config->c_info.type != LIBXL_DOMAIN_TYPE_HVM)
+        return 0;
+
+    /*
+     * Take the first defined video device (graphics card) to display
+     * on the first graphics device (display).
+     */
+    if (def->nvideos) {
+        switch (def->videos[0]->type) {
+        case VIR_DOMAIN_VIDEO_TYPE_VGA:
+        case VIR_DOMAIN_VIDEO_TYPE_XEN:
+            b_info->u.hvm.vga.kind = LIBXL_VGA_INTERFACE_TYPE_STD;
+            if (dm_type == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
+                if (def->videos[0]->vram < 16 * 1024) {
+                    virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                                   _("videoram must be at least 16MB for VGA"));
+                    return -1;
+                }
+            } else {
+                if (def->videos[0]->vram < 8 * 1024) {
+                    virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                                   _("videoram must be at least 8MB for VGA"));
+                    return -1;
+                }
+            }
+            break;
+
+        case VIR_DOMAIN_VIDEO_TYPE_CIRRUS:
+            b_info->u.hvm.vga.kind = LIBXL_VGA_INTERFACE_TYPE_CIRRUS;
+            if (dm_type == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
+                if (def->videos[0]->vram < 8 * 1024) {
+                    virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                                   _("videoram must be at least 8MB for CIRRUS"));
+                    return -1;
+                }
+            } else {
+                if (def->videos[0]->vram < 4 * 1024) {
+                    virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                                   _("videoram must be at least 4MB for CIRRUS"));
+                    return -1;
+                }
+            }
+            break;
+
+        default:
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("video type %s is not supported by libxl"),
+                           virDomainVideoTypeToString(def->videos[0]->type));
+            return -1;
+        }
+        /* vram validated for each video type, now set it */
+        b_info->video_memkb = def->videos[0]->vram;
+    } else {
+        libxl_defbool_set(&b_info->u.hvm.nographic, 1);
+    }
+
+    return 0;
+}
+
 int
 libxlDriverNodeGetInfo(libxlDriverPrivatePtr driver, virNodeInfoPtr info)
 {
@@ -1523,6 +1589,14 @@ libxlBuildDomainConfig(virPortAllocatorPtr graphicsports,
     if (libxlMakePCIList(def, d_config) < 0)
         return -1;
 
+    /*
+     * Now that any potential VFBs are defined, update the build info with
+     * the data of the primary display. Some day libxl might implicitely do
+     * so but as it does not right now, better be explicit.
+     */
+    if (libxlMakeVideo(def, d_config) < 0)
+        return -1;
+
     d_config->on_reboot = libxlActionFromVirLifecycle(def->onReboot);
     d_config->on_poweroff = libxlActionFromVirLifecycle(def->onPoweroff);
     d_config->on_crash = libxlActionFromVirLifecycleCrash(def->onCrash);

src/libxl/libxl_domain.c

@@ -510,6 +510,28 @@ libxlDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
             pcisrc->backend = VIR_DOMAIN_HOSTDEV_PCI_BACKEND_XEN;
     }
 
+    if (dev->type == VIR_DOMAIN_DEVICE_VIDEO && STREQ(def->os.type, "hvm")) {
+        int dm_type = libxlDomainGetEmulatorType(def);
+
+        switch (dev->data.video->type) {
+        case VIR_DOMAIN_VIDEO_TYPE_VGA:
+        case VIR_DOMAIN_VIDEO_TYPE_XEN:
+            if (dev->data.video->vram == 0) {
+                if (dm_type == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN)
+                    dev->data.video->vram = 16 * 1024;
+                else
+                    dev->data.video->vram = 8 * 1024;
+                }
+        case VIR_DOMAIN_VIDEO_TYPE_CIRRUS:
+            if (dev->data.video->vram == 0) {
+                if (dm_type == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN)
+                    dev->data.video->vram = 8 * 1024;
+                else
+                    dev->data.video->vram = 4 * 1024;
+            }
+        }
+    }
+
     return 0;
 }