On Wed, 3 Sep 2014, Andrey Korolyov wrote: > Given 2.1 and isa-serial output, set as ttyS0 for the guest VM with > 9600 baud rate. > > The test case is quite simple - display as much data as possible over > serial console and do not hang the system. While qemu-1.1 works > perfectly, with complaining for lost interrupts (known bug for used > guest kernel), 2.1 just hangs after some seconds, eating up all > available cpu quota. > > Test case is 'while true; dmesg; done' in serial console. I`d like to > ask to consider this bug as very serious as VM going completely > unresponsive in matter of tens of seconds and there are a lot of side > attacks to produce enough number of printk() to the ttyS0 with serial > console being set up and default settings for almost any distro in > such a way that message suppression would not work and VM can be DoSed > by an unprivileged user. > >
I tried to reproduce the described behaviour with aboriginal linux and QEMU 2.1.0 but without luck. The configurations I tried: qemu-system-i386 -cpu pentium3 -no-reboot -kernel bzImage -hda hda.sqf \ -append "root=/dev/hda rw init=/sbin/init.sh panic=1 console=ttyS0 HOST=i686" qemu-system-i386 -cpu pentium3 -no-reboot -kernel bzImage -hda hda.sqf \ -append "root=/dev/hda rw init=/bin/ash panic=1 console=ttyS0,9600 HOST=i686" With all output the system did not hang. In particular I alway could switch to QEMU monitor and stop the VM from there. Can you give an exact QEMU command line which leads to the bug? -- Kirill
