[Spice-devel] [Engine-devel] SPICE related features

[Hans de Goede]

Hi,

On 02/09/2012 09:33 AM, Itamar Heim wrote:
> On 02/09/2012 10:31 AM, Hans de Goede wrote:

<snip>

>>> so this means we need to ask the user for linux guests if they want
>>> single head or multiple heads when they choose multi monitor?
>>
>> We could ask the user, but I don't think that that is a good idea.
>>
>>> this will cause their (single) head to spin...
>>
>> With which you seem to agree :)
>>
>>> any better UX we can suggest users?
>>
>> Yes, no UI at all, the current solution using multiple single monitor
>> pci cards means using Xinerama, which disables Xrandr, and thus allows
>> no dynamic adjustment of the monitor settings of the guest, instead
>> an xorg.conf file must be written (the linux agent can generate one
>> based on the current client monitor info) and Xorg needs to be restarted.
>>
>> This is the result of the multiple pci cards which each 1 monitor model
>> we've been using for windows guests being a poor match for Linux guests.
>>
>> So we are working on adding support to drive multiple monitors from a
>> single qxl pci device. This requires changes on both the host and
>> guest side, but if both sides support it this configuration is much
>> better, so IMHO ovirt should just automatically enable it
>> if both the host (the cluster) and the guest support it.
>>
>> On the guest side, this is the current status:
>>
>> RHEL <= 6.1 no multi monitor support
>> RHEL 6.2(*) - 6.? multi monitor support using Xinerama (so 1
>> monitor/card, multiple cards)
>> RHEL >= 6.? multi monitor support using a single card with multiple outputs
>>
>> Just like when exactly the new multi mon support will be available
>> for guests, it is a similar question mark for when it will be available for
>> the host.
>
> this is the ovirt mailing list, so upstream versions are more relevant here.
> in any case, I have the same issue with backward compatibilty.
> say you fix this in fedora 17.
> user started a guest VM when host was fedora 16.
> admin upgraded host and changed cluster level to utilize new features.
> suddenly on next boot guest will move from 4 heads to single head? I'm guessing it will break user configuration.
> i.e., user should be able to choose to move to utilize the new mode?

I see this as something which gets decided at vm creation time, and then
stored in the vm config. So if the vm gets created with a guest OS which
does not support multiple monitors per qxl device, or when the cluster does
not support it, it uses the old setup with 1 card / monitor. Even if the
guest OS or the cluster gets upgraded later.

Regards,

Hans