[Pkg-xen-devel] Bug#776742: xen-utils-common: no support for VGA Passthrough

[Brian Paterni]

Package: xen-utils-common
Version: 4.4.1-6
Severity: normal

Dear Maintainer,

(There appear to be several reports on the BTS with concerns relating to
this report. Some unarchiving/merging may be necessary. Reassignment may
be needed as well since I'm not sure which package this problem would
fall under. Ultimately decided to file with xen-utils-common with 'xl'
being the frontend interface for the xen system.)


It looks like VGA passthrough is currently unsupported/broken in the xen
system packages or in its dependencies.

With gfx_passthru=0 (default), I'm able to boot a domU and access its
interface using vnc. However if I enable gfx_passthru, the domU fails to
boot, and I'm greeted with an error message telling me the device model
failed to spawn:

    libxl: error: libxl_dm.c:1371:device_model_spawn_outcome: domain 16 device model: spawn failed (rc=-3)
    libxl: error: libxl_create.c:1186:domcreate_devmodel_started: device model did not start: -3
    libxl: error: libxl_dm.c:1475:kill_device_model: Device Model already exited

According to xl.cfg(5) this is to be expected since the default
'upstream qemu-xen device-model currently does not have support for
gfx_passthru.'

xl.cfg(5) also mentions that 'gfx_passthru is currently only supported
with the qemu-xen-traditional device-model'. However if I request this
device-model be used instead with:

    device_model_version="qemu-xen-traditional"

I receive another error message mentioning that this device-model does
not exist:

    libxl: error: libxl_dm.c:1233:libxl__spawn_local_dm: device model /usr/lib/xen-4.4/bin/qemu-dm is not executable: No such file or directory
    libxl: error: libxl_dm.c:1371:device_model_spawn_outcome: (null): spawn failed (rc=-3)
    libxl: error: libxl_create.c:1186:domcreate_devmodel_started: device model did not start: -3
    libxl: error: libxl_dm.c:1467:kill_device_model: unable to find device model pid in /local/domain/17/image/device-model-pid
    libxl: error: libxl.c:1421:libxl__destroy_domid: libxl__destroy_device_model failed for 17

But again, this is to be expected since qemu-traditional support has
been removed in recent xen system packages:

    xen (4.4.0-1) unstable; urgency=medium
    
      [ Bastian Blank ]
          *** snip ***
    
      [ Ian Campbell ]
          *** snip ***
      * Disable qemu-traditional and rombios support using new configure option
        instead of by patching. No need to build-depend on ipxe any more.
          *** snip ***
    
     -- Bastian Blank <waldi at debian.org>  Sat, 09 Aug 2014 13:09:00 +0200

I understand there is a desire to shift away from qemu-xen-traditional,
and I think this is fine, but has there been any movement upstream to
add support for gfx_passthru in what is known as the 'qemu-xen'
device-model? (honest question... I'm not too familiar with qemu/xen
development) Would it be too much to ask for the re-enablement of
'qemu-traditional' in the meantime?


-- System Information:
Debian Release: 8.0
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages xen-utils-common depends on:
ii  lsb-base        4.1+Debian13+nmu1
ii  python          2.7.8-2
ii  ucf             3.0030
ii  udev            215-11
ii  xenstore-utils  4.4.1-6

xen-utils-common recommends no packages.

xen-utils-common suggests no packages.

-- no debconf information