The heavily corrupted console got me thinking and there's a more telling/simpler
way to see the problem:

Boot guest to lighdm

ssh in twice and get root.

in the 1st ssh do a   chvt 1
  This doesn't return

so that's probably the underlying problem.
In the 2nd vt I did an
echo t > /proc/sysrq-trigger

and for chvt I got:

[   85.553746] chvt            S ffff88007fd14500     0  1800   1799 0x00000000
[   85.553746]  ffff88006b8ddd08 0000000000000002 ffff88006b8ddfd8 0000000000014500
[   85.553746]  ffff88006b8ddfd8 0000000000014500 ffff880067815ec0 ffff88006b8ddd9c
[   85.553746]  ffff880067815ec0 0000000000005607 ffff880036991c00 00000000fffffffa
[   85.553746] Call Trace:
[   85.553746]  [<ffffffff81710659>] schedule+0x29/0x70
[   85.553746]  [<ffffffff8145409a>] __vt_event_wait.isra.0.part.1+0x5a/0x90
[   85.553746]  [<ffffffff81089020>] ? wake_up_atomic_t+0x30/0x30
[   85.553746]  [<ffffffff81454285>] vt_waitactive+0x65/0xb0
[   85.553746]  [<ffffffff8106e069>] ? ns_capable+0x29/0x50
[   85.553746]  [<ffffffff81454bf7>] vt_ioctl+0x7b7/0x11c0
[   85.553746]  [<ffffffff81448d5d>] tty_ioctl+0x26d/0xbc0
[   85.553746]  [<ffffffff8104f46f>] ? kvm_clock_read+0x1f/0x30
[   85.553746]  [<ffffffff8101b8a9>] ? sched_clock+0x9/0x10
[   85.553746]  [<ffffffff8109b45d>] ? sched_clock_local+0x1d/0x80
[   85.553746]  [<ffffffff811c4615>] do_vfs_ioctl+0x2e5/0x4d0
[   85.553746]  [<ffffffff8109c0b4>] ? vtime_account_user+0x54/0x60
[   85.553746]  [<ffffffff811c4881>] SyS_ioctl+0x81/0xa0
[   85.553746]  [<ffffffff8171ba7f>] tracesys+0xe1/0xe6


with the X processes in:
[   85.553746] Xorg            x ffff88007fc14500     0   950    928 0x00000000
[   85.553746]  ffff88006e48b510 0000000000000002 ffff88006e48bfd8 0000000000014500
[   85.553746]  ffff88006e48bfd8 0000000000014500 ffff880078968000 ffff880078968650
[   85.553746]  ffff880078967ff0 ffff88006d995ec0 ffff880078967ff0 ffff880078968000
[   85.553746] Call Trace:
[   85.553746]  [<ffffffff81710659>] schedule+0x29/0x70
[   85.553746]  [<ffffffff81066edf>] do_exit+0x6ff/0xa50
[   85.553746]  [<ffffffff817142af>] oops_end+0xaf/0x150
[   85.553746]  [<ffffffff810172bb>] die+0x4b/0x70
[   85.553746]  [<ffffffff817139f0>] do_trap+0x60/0x170
[   85.553746]  [<ffffffff81014512>] do_invalid_op+0xa2/0x100
[   85.553746]  [<ffffffffa00d12d6>] ? qxl_send_monitors_config+0x136/0x140 [qxl]
[   85.553746]  [<ffffffff81088ec8>] ? finish_wait+0x58/0x70
[   85.553746]  [<ffffffffa00d4a2a>] ? wait_for_io_cmd_user+0x20a/0x3c0 [qxl]
[   85.553746]  [<ffffffff8171d09e>] invalid_op+0x1e/0x30
[   85.553746]  [<ffffffffa00d12d6>] ? qxl_send_monitors_config+0x136/0x140 [qxl]
[   85.553746]  [<ffffffffa00d15da>] qxl_enc_commit+0x12a/0x220 [qxl]
[   85.553746]  [<ffffffffa00ac1b1>] drm_crtc_helper_set_mode+0x381/0x510 [drm_kms_helper]
[   85.553746]  [<ffffffffa00ad7d5>] drm_crtc_helper_set_config+0x9c5/0xb20 [drm_kms_helper]
[   85.553746]  [<ffffffffa00545fd>] drm_mode_set_config_internal+0x5d/0xe0 [drm]
[   85.553746]  [<ffffffffa00ab681>] drm_fb_helper_set_par+0x71/0xf0 [drm_kms_helper]
[   85.553746]  [<ffffffff813d1db1>] fb_set_var+0x191/0x430
[   85.553746]  [<ffffffff8109694d>] ? ttwu_do_activate.constprop.75+0x5d/0x70
[   85.553746]  [<ffffffff813deb41>] fbcon_blank+0x1d1/0x2d0
[   85.553746]  [<ffffffff8145e674>] do_unblank_screen+0xb4/0x1e0
[   85.553746]  [<ffffffff814543ba>] complete_change_console+0x5a/0xe0
[   85.553746]  [<ffffffff814553ea>] vt_ioctl+0xfaa/0x11c0
[   85.553746]  [<ffffffff81448d5d>] tty_ioctl+0x26d/0xbc0
[   85.553746]  [<ffffffff8104f46f>] ? kvm_clock_read+0x1f/0x30
[   85.553746]  [<ffffffff8101b8a9>] ? sched_clock+0x9/0x10
[   85.553746]  [<ffffffff8109b45d>] ? sched_clock_local+0x1d/0x80
[   85.553746]  [<ffffffff811c4615>] do_vfs_ioctl+0x2e5/0x4d0
[   85.553746]  [<ffffffff8109c0b4>] ? vtime_account_user+0x54/0x60
[   85.553746]  [<ffffffff811c4881>] SyS_ioctl+0x81/0xa0
[   85.553746]  [<ffffffff8171ba7f>] tracesys+0xe1/0xe6
[   85.553746] Xorg            S ffff88007fd14500     0  1168    928 0x00400000
[   85.553746]  ffff88006d83bce0 0000000000000006 ffff88006d83bfd8 0000000000014500
[   85.553746]  ffff88006d83bfd8 0000000000014500 ffff88006d995ec0 ffff88006d995ec0
[   85.553746]  0000000000000000 ffff88006d995ec0 ffff88006d83bd88 ffffffff81f17608
[   85.553746] Call Trace:
[   85.553746]  [<ffffffff81710659>] schedule+0x29/0x70
[   85.553746]  [<ffffffff810cd55d>] futex_wait_queue_me+0xdd/0x140
[   85.553746]  [<ffffffff810ce202>] futex_wait+0x182/0x290
[   85.553746]  [<ffffffff81098810>] ? wake_up_state+0x10/0x20
[   85.553746]  [<ffffffff810cd626>] ? wake_futex+0x66/0x80
[   85.553746]  [<ffffffff8104f46f>] ? kvm_clock_read+0x1f/0x30
[   85.553746]  [<ffffffff8104f46f>] ? kvm_clock_read+0x1f/0x30
[   85.553746]  [<ffffffff810d040e>] do_futex+0xde/0x670
[   85.553746]  [<ffffffff8110b1ac>] ? acct_account_cputime+0x1c/0x20
[   85.553746]  [<ffffffff8109ba8c>] ? account_user_time+0x8c/0xa0
[   85.553746]  [<ffffffff810d0a11>] SyS_futex+0x71/0x150
[   85.553746]  [<ffffffff81020e15>] ? syscall_trace_enter+0x145/0x250
[   85.553746]  [<ffffffff8171ba7f>] tracesys+0xe1/0xe6
[   85.553746] Xorg            S ffff88007fd14500     0  1169    928 0x00400000
[   85.553746]  ffff88006d861ce0 0000000000000006 ffff88006d861fd8 0000000000014500
[   85.553746]  ffff88006d861fd8 0000000000014500 ffff88006d994710 ffff88006d994710
[   85.553746]  0000000000000000 ffff88006d994710 ffff88006d861d88 ffffffff81f16180
[   85.553746] Call Trace:
[   85.553746]  [<ffffffff81710659>] schedule+0x29/0x70
[   85.553746]  [<ffffffff810cd55d>] futex_wait_queue_me+0xdd/0x140
[   85.553746]  [<ffffffff810ce202>] futex_wait+0x182/0x290
[   85.553746]  [<ffffffff8104f46f>] ? kvm_clock_read+0x1f/0x30
[   85.553746]  [<ffffffff8104f46f>] ? kvm_clock_read+0x1f/0x30
[   85.553746]  [<ffffffff810d040e>] do_futex+0xde/0x670
[   85.553746]  [<ffffffff8110b1ac>] ? acct_account_cputime+0x1c/0x20
[   85.553746]  [<ffffffff8109ba8c>] ? account_user_time+0x8c/0xa0
[   85.553746]  [<ffffffff810d0a11>] SyS_futex+0x71/0x150
[   85.553746]  [<ffffffff81020e15>] ? syscall_trace_enter+0x145/0x250
[   85.553746]  [<ffffffff8171ba7f>] tracesys+0xe1/0xe6