virtio-gpu: Hang on shutdown after suspend/resume with virtio

[Christian Borntraeger <borntraeger@de.ibm.com>]

Gerd,

another thing with virtio-gpu.

I can successfully do suspend/resume (echo disk > /sys/power/state) on my system. As soon as I have a
virtio-gpu the system hangs on reboot/shutdown:

e.g.

crash> bt 1
PID: 1      TASK: 6bef0000          CPU: 4   COMMAND: "systemd"
 #0 [6beef4c0] __schedule at a55d60
 #1 [6beef530] schedule at a563f2
 #2 [6beef548] virtio_gpu_queue_ctrl_buffer_locked at 7ea708
 #3 [6beef650] virtio_gpu_queue_ctrl_buffer at 7ea830
 #4 [6beef680] virtio_gpu_primary_plane_update at 7ed5ee
 #5 [6beef710] drm_atomic_helper_commit_planes at 7a2b46
 #6 [6beef760] vgdev_atomic_commit_tail at 7e9dbc
 #7 [6beef790] commit_tail at 7a7126
 #8 [6beef7c0] drm_atomic_helper_commit at 7a73fe
 #9 [6beef800] restore_fbdev_mode_atomic at 7aa38a
#10 [6beef8a0] drm_fb_helper_pan_display at 7ab7aa
#11 [6beef8f0] fb_pan_display at 74a248
#12 [6beef928] bit_update_start at 7573c0
#13 [6beef958] fbcon_switch at 7542b4
#14 [6beefa50] redraw_screen at 77b2b8
#15 [6beefaa0] csi_J at 77b476
#16 [6beefad8] do_con_trol at 77ee12
#17 [6beefb40] do_con_write at 77f80c
#18 [6beefc10] con_write at 78003c
#19 [6beefc40] n_tty_write at 7662d4
#20 [6beefce0] tty_write at 761734
#21 [6beefd48] __vfs_write at 3483cc
#22 [6beefe00] vfs_write at 3486e8
#23 [6beefe60] sys_write at 3489de
#24 [6beefea8] system_call at a5b6a8
 PSW:  0705100180000000 000003ff8111251c (user space)
 GPRS: 0000000000000000 000003ff00000002 000000000000000e 000003ff80deaef0 
       000000000000000a 0000000000000000 000000000000000f 00000000000003ef 
       0000000000000000 000000000000000e 000003ff80deaef0 000000000000000a 
       000003ff81228f58 000000000000000e 000003ff81112510 000003fffdefedf8 




Turns out that the virtio-gpu console (via vnc) prints the image loading but then
stops and show no login prompt. (but agetty is running on tty1) So I assume it 
already hangs after resume (and I am working on the serial sclp console).

Does suspend resume works for you with virtio-gpu on x86? If yes, then I would
not to look into the s390 code (virtio-blk and net seems to work fine). Otherwise
it would be good if you could have a look.

Christian