KVM and Xen guest fail with cirrus emulated graphic card

Pekka Paalanen ppaalanen at gmail.com
Thu Nov 24 12:06:43 UTC 2016

On Mon, 21 Nov 2016 17:55:28 +0100
Dario Faggioli <dario.faggioli at citrix.com> wrote:

> Hello,
> I've recently tried Fedora 25 inside both a KVM and Xen guest. In both
> cases, the emulated graphic card selected by default is the "bad old"
> Cirrus.
> So, as I reported in my comment to this (already existing) bug:
> https://bugzilla.redhat.com/show_bug.cgi?id=1227770
>  - on Wayland, with Cirrus as emulated graphic card, I don't see the 
>    GNOME login screen appearing.
>  - if I keep Cirrus and disable Wayland (via /etc/gdm/custom.conf),
>    both Xen and KVM guests works ok.
>  - if I keep wayland and use a different graphic card (vga or qxl, for
>    instance), both Xen and KVM guests works ok.
> There's not much information online, and what's there suggests that it
> may be due to the hw characteristics of Cirrus (e.g., the 24bpp thing),
> which are not supported by Wayland.
> The issue has been brought up and is being discussed in this thread
> too:
> https://lists.xen.org/archives/html/xen-devel/2016-11/msg01579.html
> Now, what we're interested to know is, if possible:
>  - how we can actually figure out what the issue is
>    (I've poked around, but haven't found much in any log)?
>  - is it something that can be made to work? If yes, is
>    it likely to happen, or will this be a 'won't fix'?
> This is relevant because, as I said, for both for KVM and Xen, what
> we're getting _by_default_ is a non working guest, if Wayland is used.
> :-(
> Thanks and Regards,
> Dario
> PS. please, keep me in Cc, if possible, as I'm not subscribed right
> now...


Wayland does not do anything with any hardware. You might want to
contact the display server project, i.e. gnome-shell or whatever is
running there. Display servers (Wayland compositors) deal with
hardware, Wayland does not.

wayland-devel@ would the right address if this problem is present on

...Assuming you really insist on using Cirrus which by sounds of the other
comments is your actual bug. Otherwise you will need to test and fix
every single Wayland compositor out there.

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