Re: qemu-kvm 0.12.4 hanging forever

[Brian Jackson <iggy@theiggy.com>]

On Thursday, July 01, 2010 05:37:29 pm Zach Carter wrote:
> Hi:
> 
> Under certain 100% reproducible circumstances, when I try to run qemu-kvm,
> it completely hangs without appearing to do anything
> 
> I have tried this with qemu-kvm 0.12.4 and with the latest code from the
> git repository.
> 
> Here are some more interesting details.  The 64 bit host, kernel, and kvm
> kernel module are all vanilla CentOS 5.4.  If I use the kmod-
> kvm-83-105.el5_4.9 version of the kernel module, it works fine.  Yum update
> to anything past that and the hang occurs 100% of the time.  Update all
> the way to the very latest CentOS 5.5 packages, and I still get the hang. 
> Downgrade just the kvm kernel modules and it starts working again.


That's pretty well known. Use a newer kernel with a newer qemu-kvm, or use the 
packages that come with CentOS.


> 
> I'm sure I could use the qemu-kvm that ships from CentOS with the
> corresponding kernel module, however that lacks certain essential features,
> including support for scsi disk drive emulation.


There's a reason Redhat disables scsi support in their kvm... it's not really 
suggested to use it.


> 
> After messing around with gdb and some printf statements, it looks to me
> like it just loops forever and ever in the "while (1)" loop on about line
> 1710 of qemu-kvm.c.   Killing it and grabbing a backtrace shows that it is
> spending its time mostly sitting in the "select" system call on about line
> 1288 in vt.c.  Maybe its normal to sit in that loop and poll for events,
> but something else should happen eventually.  What is it waiting for?
> 
> If I add the -no-kvm option to the command line, it works fine.
> 
> Any ideas on how to further troubleshoot?
> 
> thanks!
> 
> -Zach
> 
> My command line:
> 
> /opt/qemu-git/bin/qemu-system-x86_64 -drive
> file=my.vmdk,if=scsi,cache=writeback -cdrom my.iso -boot d -nographic -m
> 1024 - no-kvm-irqchip -kernel my.vmlinuz -initrd my.initrd.img -append
> 'initrd=initrd.img root=/dev/ram0 console=tty0 console=ttyS0,19200 quiet
> action=install mode=silent ramdisk_size=147169 mkvm_cpu_lm
> mkvm_device=/dev/sda mkvm'
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