[Qemu-devel] qemu and software suspend

[ace]

Hi.

Has somebody tried to hibernate Linux while qemu is running?
Here is my experience:
1. I was running qemu 0.7.2 fullscreen (under X with SDL),
on Linux 2.6.14 host, with Win95 quest. All was fine,
together with kqemu.
2. I changed to a virtual console and initiated hibernate
(software suspend2 2.2-rc9). Everything latest stuff :)
3. That's when weird things started. The kernel throwed
a "BUG", with the usual instruction and stack dump. The
offending process was kswapd0.
4. But it successfully hibernated anyway. This was my first
kernel complaint at hibernating ever.
5. After resuming the machine later, it seemed to work fine.
I switched to qemu, but it was almost dead. Actually, qemu
was fine, but the guest OS was almost dead. I could move
application windows a bit, click on things to select them,
but all this stopped after a while (seconds) and it didn't
respond again. But qemu was going along. I could toggle
fullscreen and it was taking 100% CPU (which is correct
here). The management console worked fine.
6. On the host side, I noticed kswapd0 (kernel swap thread)
was killed, but the OS still swapped fine.
7. I couldn't wake win95 so I had to quit qemu.

My questions:
1. May there be a problem with the kqemu module? Does
it have proper suspend/resume routines? Or it doesn't need
them (it is not a device driver)?
2. Can the problem also be inside Win95? What happens
in qemu when the time in the host system suddenly changes?
Mine skipped 20 hours. Does the time in the quest continue
without skips, thus the guest has different time than the
host? Before win95 completelly stopped responding, it showed
the old time from before the suspending on the taskbar.
Or does qemu synchronise the time to the host? But I doubt
that, mine was drifting behind even without suspending, the
machine is quite slow.

I'd like to ask if suspending with qemu is officially
declared "A bad thing to do", or it should work, but I have
something wrong with my system. I run latest Slackware 10.2
on a Pentium MMX.

Peter