Re: qemu-system-x86_64 locks hard when used with kvm

[Jan Frey <linux-vNYXhaxa7OiELgA04lAiVw@public.gmane.org>]

On Wednesday 24 October 2007, Amit Shah wrote:
> On Monday 15 October 2007 01:54:03 Jan Frey wrote:
> > Hi,
> >
> > I intended to use qemu-system-x86_64 with kvm for full virtualization.
> > My host is
> >
> > # cat /proc/cpuinfo
> > processor       : 0
> > vendor_id       : AuthenticAMD
> > cpu family      : 15
> > model           : 127
> > model name      : AMD Athlon(tm) 64 Processor 3500+
> > stepping        : 1
> > cpu MHz         : 1000.000
> > cache size      : 512 KB
> > fpu             : yes
> > fpu_exception   : yes
> > cpuid level     : 1
> > wp              : yes
> > flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> > mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext
> > fxsr_opt rdtscp lm 3dnowext 3dnow rep_good pni cx16 lahf_lm svm
> > extapic cr8_legacy misalignsse
> > bogomips        : 2010.55
> > TLB size        : 1024 4K pages
> > clflush size    : 64
> > cache_alignment : 64
> > address sizes   : 40 bits physical, 48 bits virtual
> > power management: ts fid vid ttp tm stc 100mhzsteps
> >
> >
> > So you can see AMD's "svm" is existent.
> > Host's kernel is 2.6.23.1, config file is attached.
> > KVM/Qemu sources I've tried include -37, -40, -45 and -46.
> >
> > When I run something like
> > qemu-system-x86_64 -m 384 -no-kvm <somevdisk>
> >
> > The virtual machine boots and everything works fine (except the
> > slowliness ;-)).
> > But when I try without the "-no-kvm" switch the whole host machine
> > immediately freezes hard (no windows come up, no text on the console,
> > mouse frozen, amazing though that machine still reacts to ping on
> > network.. but anyway, even reset button at the PC doesn't help, I've
> > got to switch off power..)
> >
> > The host distribution is FC6.
>
> That's really strange. I use kvm (frequently updated to the latest git)
> daily and I don't face any such issues.
>
> Can you try this:
>
> Don't load the kvm modules (or rmmod kvm-amd; rmmod kvm if they're
> already loaded) and then try the qemu command line without --no-kvm?
> Does it lock up even then?

It complains about missing /dev/kvm, but it seems to work.
insmod'ing only kvm also doesn't break it. As soon as kvm-amd comes into 
play: immediate freeze upon qemu-system-x86_64 start.

> Also, can you try what you've tried previously on a text console (not
> within X). If there's any kernel output, it'll be dumped.

I did the tests in runlevel 3 on a root console. Same result: absolutely no 
output and the very instant I press <return> (following the 
qemu-system-x86_64 commandline) my machine is dead. Video is still up, but 
there's no way to shake it - as I mentioned before even the mainboard's 
reset button does not bring it back to live (and usually it does)...

Regards,
Jan



-- 
Jan Frey
linux [at] janfrey.de

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