Xen: Defer setting default vram value to Xen drivers

Allow the Xen drivers to determine default vram values.  Sane
default vaules depend on the device model being used, so the
drivers are in the best position to determine the defaults.

For the legacy xen driver, it is best to maintain the existing
logic for setting default vram values to ensure there are no
regressions.  The libxl driver currently does not support
configuring a video device.  Support will be added in a
subsequent patch, where the benefit of this change will be
reaped.
Signed-off-by: NJim Fehlig <jfehlig@suse.com>

src/conf/domain_conf.c

@@ -9953,6 +9953,10 @@ int
 virDomainVideoDefaultRAM(const virDomainDef *def,
                          int type)
 {
+    /* Defer setting default vram to the Xen drivers */
+    if (def->virtType == VIR_DOMAIN_VIRT_XEN)
+        return 0;
+
     switch (type) {
         /* Weird, QEMU defaults to 9 MB ??! */
     case VIR_DOMAIN_VIDEO_TYPE_VGA:

src/xen/xen_driver.c

@@ -353,6 +353,25 @@ xenDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
         return -1;
     }
 
+    if (dev->type == VIR_DOMAIN_DEVICE_VIDEO && dev->data.video->vram == 0) {
+        switch (dev->data.video->type) {
+        case VIR_DOMAIN_VIDEO_TYPE_VGA:
+        case VIR_DOMAIN_VIDEO_TYPE_CIRRUS:
+        case VIR_DOMAIN_VIDEO_TYPE_VMVGA:
+            dev->data.video->vram = 9 * 1024;
+        break;
+
+        case VIR_DOMAIN_VIDEO_TYPE_XEN:
+            /* Original Xen PVFB hardcoded to 4 MB */
+            dev->data.video->vram = 4 * 1024;
+            break;
+
+        case VIR_DOMAIN_VIDEO_TYPE_QXL:
+            /* Use 64M as the minimal video video memory for qxl device */
+            return 64 * 1024;
+        }
+    }
+
     return 0;
 }