Re: Second KVM process hangs eating 80-100% CPU on host during startup

[Alex Davis <alex14641@yahoo.com>]

--- On Fri, 4/18/08, Avi Kivity <avi@qumranet.com> wrote:

> From: Avi Kivity <avi@qumranet.com>
> Subject: Re: [kvm-devel] Second KVM process hangs eating 80-100% CPU on host during startup
> To: "Alex Davis" <alex14641@yahoo.com>
> Cc: kvm-devel@lists.sourceforge.net
> Date: Friday, April 18, 2008, 12:12 PM
> Alex Davis wrote:
> > Host software:
> > Linux 2.6.24.4
> > KVM 65 (I am using the kernel modules from this
> release).
> > X11 7.2 from Xorg
> > SDL 1.2.13
> > GCC 4.1.1
> > Glibc 2.4
> >
> > Host hardware:
> > Asus P5B Deluxe (P965 chipset based) motherboard
> > 4 GB RAM
> > Intel E6700 CPU
> >
> > Guest software:
> > Slackware 12.0 installed from CD-ROM.
> >
> > Command used to first KVM instance:
> > /usr/local/bin/qemu-system-x86_64 -hda
> /spare/vdisk1.img -cdrom /dev/cdrom -boot c -m 384 -net
> > nic,macaddr=DE:AD:BE:EF:11:29 -net
> tap,ifname=tap0,script=no &
> >
> > Command used to start second KVM instance:
> > /usr/local/bin/qemu-system-x86_64 -hda
> /spare/vdisk2.img -cdrom /dev/cdrom -boot c -m 384 -net
> > nic,macaddr=DE:AD:BE:EF:11:30 -net
> tap,ifname=tap1,script=no &
> >
> > tap0 and tap1 are bridged on the host. The guest OS
> was installed on /spare/vdisk1.img, 
> > which was initially created by /usr/local/bin/qemu-img
> create -f qcow /spare/vdisk.img 10G
> > After the guest installation completed, vdisk1 was
> copied to vdisk2.
> >
> > The second instance always stops after printing
> > Checking if the processor honours the WP bit even in
> supervisor mode... Ok.
> > It stays hung until I press the return key in the
> first instance; sometimes clicking in another X
> > window will wake it up as well. 
> >
> > This is a test machine so I can test patches (almost)
> at will.
> >
> >   
> 
> Strange.  Does pinning each guest to a different cpu help
> (use 'taskset 
> 1 qemu ... vdisk1.img &  ', taskset 2 qemu ...
> vdisk2.img)
> 
> 

taskset made no difference. Upgrading to kvm-66 didn't help either.
 
> Any sufficiently difficult bug is indistinguishable from a
> feature.


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