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[Xen-users] xm create of a VMX fails - qemu-dm gets SIGSEGV

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Subject: [Xen-users] xm create of a VMX fails - qemu-dm gets SIGSEGV
From: Steve Dobbelstein <steved@xxxxxxxxxx>
Date: Wed, 30 Nov 2005 18:09:47 -0600
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Greetings, all.

I'm having trouble getting a VMX domain started.  I'm running on changeset
8119.  Shortly after the "xm create" finishes the qemu-dm process goes
defunct.  I wrote a little script so that strace could attach to the
qemu-dm process right after the "xm create" finishes:

xm create $1
pid=`ps ax|grep qemu-dm|grep -v grep|awk '{print $1}'`
echo qemu-dm pid is $pid
echo strace -p $pid
strace -p $pid

Here is a sample of the strace output from one of the runs:
(See attached file: strace.qemu-dm)

It appears that the qemu-dm process is getting a SIGSEGV.

I noticed from some other runs that the qemu-dm process is getting launched

[root@dib ~]# xm create /tmp/vmx1.cfg;ps ax|grep qemu
Using config file "/tmp/vmx1.cfg".
Started domain vmx1
 9583 ?        R      0:00 /usr/lib/xen/bin/qemu-dm -d 16 -p 3 -m 768 -boot
c -localtime -serial pty -vcpus 1 -hda /dev/sdb -macaddr 00:16:3e:61:5f:87
-bridge xenbr0 -nographic
 9586 ?        R      0:00 /usr/lib/xen/bin/qemu-dm -d 16 -p 3 -m 768 -boot
c -localtime -serial pty -vcpus 1 -hda /dev/sdb -macaddr 00:16:3e:61:5f:87
-bridge xenbr0 -nographic
 9590 pts/1    S+     0:00 grep qemu

On another occasion it was the qemu-ifup that had two occurrences running:

[root@dib ~]# xm create /tmp/vmx1.cfg;ps ax|grep qemu
Using config file "/tmp/vmx1.cfg".
Started domain vmx1
10019 ?        S      0:00 /usr/lib/xen/bin/qemu-dm -d 17 -p 3 -m 768 -boot
c -localtime -serial pty -vcpus 1 -hda /dev/sdb -macaddr 00:16:3e:53:48:e4
-bridge xenbr0 -nographic
10022 ?        R      0:00 /bin/sh /etc/xen/qemu-ifup tun0 xenbr0
10023 ?        R      0:00 /bin/sh /etc/xen/qemu-ifup tun0 xenbr0
10027 pts/0    S+     0:00 grep qemu

Is this normal?  Two occurrences of the same program sounds like asking for
contention trouble, but then I am fairly clueless about the mechanics of
how VMX sessions work.

I will note that this worked on the same machine with changeset 8112.
(Well, I only once saw a VMX boot all the way once.  Subsequent attempts
using vnc, sdl, and serial output all started to boot but each ran into its
own problems during the boot.)  Now nothing appears to start since qemu-dm
dies shortly after it is launched.

Here is the output from xen-bugtool.  I should note that it is from a run
after the run done with the strace above.
(See attached file: xen-bugtool_xm-create-vmx.tar.bz2)

Here is the config file for creating the VMX domain.
(See attached file: vmx1.cfg)

Any help on solving the problem or pointers to where to look will be

Steve D.

P.S.  I notice that "xm list" lists the VMX domain in the blocked state.
Is this a bug?  It seems to me that if qemu is dead that Xen should pick up
on that, clean up its records of the domain and take the appropriate action
for a crashed domU.  Just a thought.

Attachment: strace.qemu-dm
Description: Binary data

Attachment: xen-bugtool_xm-create-vmx.tar.bz2
Description: Binary data

Attachment: vmx1.cfg
Description: Binary data

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