[libvirt] [PATCH] libxl: fix default vram setting for implicit video device

[Joao Martins]

On 05/11/2016 06:01 AM, Jim Fehlig wrote:
> Commit 6879be48 moved adding of an implicit video device after XML
> parsing. As a result, libxlDomainDeviceDefPostParse() is no longer
> called to set the default vram when adding an implicit device.
> Commit 6879be48 assumes virDomainVideoDefaultRAM() will set the
> default vram, but it returns 0 if the domain virtType is
> VIR_DOMAIN_VIRT_XEN. Attempting to start an HVM domain with vram=0
> results in
> 
> error: unsupported configuration: videoram must be at least 4MB for CIRRUS
> 
> The default vram setting for Xen HVM domains depends on the device
> model used (qemu-xen vs qemu-traditional), hence setting the
> default is deferred to libxlDomainDeviceDefPostParse().
> 
> This patch addresses the problem during creation of the video
> device. If vram is 0, it is assumed unset and the default
> (depending on qemu-xen vs qemu-traditional) is applied.

Hmm, What about letting (xen) libxl decide that? If vram is set to 0 we would
set video_memkb to LIBXL_MEMKB_DEFAULT and have (xen) libxl decide the defaults
and latter update def with the value libxl set back? Altough these values are
well established defaults, these might change on libxl in which case prevent
domain creation.

> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1334557
> Signed-off-by: Jim Fehlig <jfehlig at suse.com>
> ---
>  src/libxl/libxl_conf.c | 38 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c
> index d927b37..1973ded 100644
> --- a/src/libxl/libxl_conf.c
> +++ b/src/libxl/libxl_conf.c
> @@ -1916,6 +1916,40 @@ libxlMakePCIList(virDomainDefPtr def, libxl_domain_config *d_config)
>      return -1;
>  }
>  
> +static unsigned int
> +libxlVideoDefaultRAM(const virDomainVideoType type, int dm_type)
> +{
> +    unsigned int ret = 0;
> +
> +    switch (type) {
> +    case VIR_DOMAIN_VIDEO_TYPE_VGA:
> +    case VIR_DOMAIN_VIDEO_TYPE_XEN:
> +        if (dm_type == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN)
> +            ret = 16 * 1024;
> +        else
> +            ret = 8 * 1024;
> +        break;
> +
> +    case VIR_DOMAIN_VIDEO_TYPE_CIRRUS:
> +        if (dm_type == LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN)
> +            ret = 8 * 1024;
> +        else
> +            ret = 4 * 1024;
> +        break;
> +
> +#ifdef LIBXL_HAVE_QXL
> +    case VIR_DOMAIN_VIDEO_TYPE_QXL:
> +        ret = 128 * 1024;
> +        break;
> +#endif
> +
> +    default:
> +        break;
> +    }
> +
> +    return ret;
> +}
> +
>  static int
>  libxlMakeVideo(virDomainDefPtr def, libxl_domain_config *d_config)
>  
> @@ -1931,6 +1965,10 @@ libxlMakeVideo(virDomainDefPtr def, libxl_domain_config *d_config)
>       * on the first graphics device (display).
>       */
>      if (def->nvideos) {
> +        if (def->videos[0]->vram == 0)
> +            def->videos[0]->vram = libxlVideoDefaultRAM(def->videos[0]->type,
> +                                                        dm_type);
> +
>          switch (def->videos[0]->type) {
>          case VIR_DOMAIN_VIDEO_TYPE_VGA:
>          case VIR_DOMAIN_VIDEO_TYPE_XEN:
>