Hello,
I have an (as far as I understand it) complex problem. I just got some
good debugging hints, so I tried some more things and reproduced the
problem with recent KVM.
I tested it now with kvm-76 (both kernel and userspace) with virtio
Ethernet on Linux 2.6.27-rc7. The guest runs Windows Server 2003
(Standard Edition, SP2) with the virtio guest driver (Version
5.1.0.3107).
First a description of my environment. I start KVM's qemu:
/usr/local/bin/qemu-system-x86_64 -m 3584 -boot n -hda hda.dat \
-net nic,macaddr=00:50:56:24:0b:37,model=virtio \
-net tap,ifname=vm03,script=no,downscript=no \
-usb -usbdevice tablet
This does a DHCP request via an etherboot virtio rom; it reports the
version as Etherboot 5.4.3, the MD5 sum is:
9b3dbc97cc819508f2984ac00b90adc0 /usr/local/share/qemu/pxe-virtio.bin
This starts pxegrub; pxegrub configuration is compiled-in and boots
from harddisk:
default 0
timeout 5
title boot from first disk
root (hd0)
chainloader +1
(This is our way of configuring DHCP to boot the locally-installed
Windows. In order to boot a network Linux, the DHCP configuration is
automatically changed.)
Now the problem: When I reboot Windows (shutdown /r), the newly booted
windows hangs during boot. (The problem stays the same when I reset
the VM (using the monitor command "system_reset") instead of rebooting
with "shutdown /r".) It hangs in the first graphical screen (where
the windows logo and "Microsoft Windows Server 2003" are displayed in
the center), and the "activity bar" below this stops after some
seconds (and qemu starts eating 100% CPU). Resetting the VM with
"system_reset" does not solve the problem; the next booted Windows
hangs in the same place.
There are many ways that make the problem disappear:
When I stop the qemu process and start a new one, Windows boots again
(but the problem can be reproduced by rebooting Windows as described
above).
When I reset the VM with "system_reset", boot Linux (Version 2.6.25.9)
from network, reboot this Linux and then boot Windows again, it works.
When I use the Realtek network driver (model=rtl8139), Windows boots
again.
When I do not use the network boot, etherboot and pxegrub sequence
(using "-boot c" instead of "-boot n"), Windows boots again.
And now the real fun: when I remove the "-usb -usbdevice tablet"
option (and this is the only change!), everything works. (It is the
"-usb" part that makes the difference, "-usbdevice tablet" doesn't
influence this problem.) I have no idea how virtio Ethernet and USB
interact in order to cause this problem...
Trying a summary: When using virtio Ethernet and "-usb"; Windows
leaves something (virtio Ethernet or USB ?) in a state that isn't
reset by my reboot sequence (etherboot/pxegrub) and makes the next
Windows boot hang. Booting Linux inbetween resets that state, and
using the "-boot c" path does that too.
So my first workaround would be to not use the USB tablet, because
this isn't critical for me. But it took us some time to diagnose the
problem, hence I wanted to tell you about this in order to save you
the same work.
Sven
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