Re: [Xen-devel] [libvirt] [PATCH v2] libxl: Implement basic video device selection

[Stefan Bader <stefan.bader@xxxxxxxxxxxxx>]

On 04.04.2014 15:17, Daniel P. Berrange wrote:
> On Fri, Apr 04, 2014 at 11:36:39AM +0200, Stefan Bader wrote:
>> +static int
>> +libxlSetBuildGraphics(virDomainDefPtr def, libxl_domain_config *d_config)
>> +{
>> +    libxl_domain_build_info *b_info = &d_config->b_info;
>> +
>> +    /*
>> +     * Take the first defined video device (graphics card) to display
>> +     * on the first graphics device (display).
>> +     * Right now only type and vram info is used and anything beside
>> +     * type xen and vga is mapped to cirrus.
>> +     */
>> +    if (def->nvideos) {
>> +        unsigned int min_vram = 8 * 1024;
>> +
>> +        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;
>> +                /*
>> +                 * Libxl enforces a minimal VRAM size of 8M when using
>> +                 * LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL or
>> +                 * 16M for LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN.
>> +                 * Avoid build failures and go with the minimum if less
>> +                 * is specified.
>> +                 */
>> +                switch (b_info->device_model_version) {
>> +                    case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL:
>> +                        min_vram = 8 * 1024;
>> +                        break;
>> +                    case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN:
>> +                    default:
>> +                        min_vram = 16 * 1024;
>> +                }
>> +                break;
>> +            default:
>> +                /*
>> +                 * Ignore any other device type and use Cirrus. Again fix
>> +                 * up the minimal VRAM to what libxl expects.
>> +                 */
> 
> We shouldn't do that 'default'. For any device type that Xen can't support
> we should report  VIR_ERR_CONFIG_UNSUPPORTED.

Ok, I could remove that. At some point it might be possible to enhance that
again. But that requires more careful thinking. At least with
device_model_version QEMU_XEN (not QEMU_XEN_TRADITIONAL and not to confuse with
device_model which just sets the path ;)) at least in theory there should be the
same support as for kvm... Anyway, just loud thinking.

Would you also rather want the VRAM fixup to be removed as well? I probably wait
a bit more for other feedback and then would do a v3...

-Stefan
> 
> Regards,
> Daniel
>

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