[PATCH v2] libxl: Allow 4 MB of video RAM for Cirrus graphics on traditional QEMU

[Rob Hoes <rob.hoes@citrix.com>]

VMs using Cirrus graphics have always had 4 MB of video RAM on XenServer, while
libxl currently does not allow values less than 8 MB.

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
Tested-by: Fabio Fantoni <fabio.fantoni@m2r.biz>

----
v2: Fixed style issues.
---
 docs/man/xl.cfg.pod.5      |   18 ++++++++-------
 tools/libxl/libxl_create.c |   53 ++++++++++++++++++++++++++++++++++----------
 2 files changed, 51 insertions(+), 20 deletions(-)

diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index 278dba1..d2d8921 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -1028,14 +1028,16 @@ in the B<VFB_SPEC_STRING> for configuring virtual frame buffer devices
 Sets the amount of RAM which the emulated video card will contain,
 which in turn limits the resolutions and bit depths which will be
 available.
-The default amount of video ram for stdvga is 8MB which is sufficient
-for e.g. 1600x1200 at 32bpp and videoram option is currently working
-only when using the qemu-xen-traditional device-model.
-
-When using the emulated Cirrus graphics card (B<vga="cirrus">)
-the amount of video ram is fixed at 4MB which is sufficient
-for 1024x768 at 32 bpp and videoram option is currently working
-only when using the upstream qemu-xen device-model.
+
+When using the qemu-xen-traditional device-model, the default as well as
+minimum amount of video RAM for stdvga is 8 MB, which is sufficient for e.g.
+1600x1200 at 32bpp. For the upstream qemu-xen device-model, the default and
+minimum is 16 MB.
+
+When using the emulated Cirrus graphics card (B<vga="cirrus">) and the
+qemu-xen-traditional device-model, the amount of video RAM is fixed at 4 MB,
+which is sufficient for 1024x768 at 32 bpp. For the upstream qemu-xen
+device-model, the default and minimum is 8 MB.
 
 =item B<stdvga=BOOLEAN>
 
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index 1b320d3..9d793ba 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -216,20 +216,51 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc,
         if (b_info->shadow_memkb == LIBXL_MEMKB_DEFAULT)
             b_info->shadow_memkb = 0;
 
-        if (b_info->u.hvm.vga.kind == LIBXL_VGA_INTERFACE_TYPE_STD &&
-            b_info->device_model_version ==
-            LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {
+        if (!b_info->u.hvm.vga.kind)
+            b_info->u.hvm.vga.kind = LIBXL_VGA_INTERFACE_TYPE_CIRRUS;
+
+        switch (b_info->device_model_version) {
+        case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL:
+            switch (b_info->u.hvm.vga.kind) {
+            case LIBXL_VGA_INTERFACE_TYPE_STD:
+                if (b_info->video_memkb == LIBXL_MEMKB_DEFAULT)
+                    b_info->video_memkb = 8 * 1024;
+                if (b_info->video_memkb < 8 * 1024) {
+                    LOG(ERROR, "videoram must be at least 8 MB for STDVGA on QEMU_XEN_TRADITIONAL");
+                    return ERROR_INVAL;
+                }
+                break;
+            case LIBXL_VGA_INTERFACE_TYPE_CIRRUS:
+            default:
+                if (b_info->video_memkb == LIBXL_MEMKB_DEFAULT)
+                    b_info->video_memkb = 4 * 1024;
+                if (b_info->video_memkb != 4 * 1024)
+                    LOG(WARN, "ignoring videoram other than 4 MB for CIRRUS on QEMU_XEN_TRADITIONAL");
+                break;
+            }
+            break;
+        case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN:
+        default:
+            switch (b_info->u.hvm.vga.kind) {
+            case LIBXL_VGA_INTERFACE_TYPE_STD:
                 if (b_info->video_memkb == LIBXL_MEMKB_DEFAULT)
                     b_info->video_memkb = 16 * 1024;
-                else if (b_info->video_memkb < (16 * 1024) ){
-                    LOG(ERROR, "videoram must be at least 16 mb with stdvga");
+                if (b_info->video_memkb < 16 * 1024) {
+                    LOG(ERROR, "videoram must be at least 16 MB for STDVGA on QEMU_XEN");
+                    return ERROR_INVAL;
+                }
+                break;
+            case LIBXL_VGA_INTERFACE_TYPE_CIRRUS:
+            default:
+                if (b_info->video_memkb == LIBXL_MEMKB_DEFAULT)
+                    b_info->video_memkb = 8 * 1024;
+                if (b_info->video_memkb < 8 * 1024) {
+                    LOG(ERROR, "videoram must be at least 8 MB for CIRRUS on QEMU_XEN");
                     return ERROR_INVAL;
                 }
-        } else if (b_info->video_memkb == LIBXL_MEMKB_DEFAULT)
-            b_info->video_memkb = 8 * 1024;
-        else if (b_info->video_memkb < (8 * 1024) ){
-            LOG(ERROR,"videoram must be at least 8 mb");
-            return ERROR_INVAL;
+                break;
+            }
+            break;
         }
 
         if (b_info->u.hvm.timer_mode == LIBXL_TIMER_MODE_DEFAULT)
@@ -254,8 +285,6 @@ int libxl__domain_build_info_setdefault(libxl__gc *gc,
             if (!b_info->u.hvm.boot) return ERROR_NOMEM;
         }
 
-        if (!b_info->u.hvm.vga.kind)
-            b_info->u.hvm.vga.kind = LIBXL_VGA_INTERFACE_TYPE_CIRRUS;
         libxl_defbool_setdefault(&b_info->u.hvm.vnc.enable, true);
         if (libxl_defbool_val(b_info->u.hvm.vnc.enable)) {
             libxl_defbool_setdefault(&b_info->u.hvm.vnc.findunused, true);
-- 
1.7.10.4