Comment 17 for bug 457716

=Comment: #0=================================================
SANTWANA SAMANTRAY <email address hidden> -

virsh save of the kvm guest hangs in Fedora12 rawhide.
After this, virsh doesn't respond properly, and even restarting libvirtd doesn't help.

Attachment: dmesg and strace of virsh save

[root@mx3550 ~]# strace -o virsh_save -f virsh save rhel6 /home/latest_save
-------HANGS HERE-----------

uname -a :Linux mx3550.in.ibm.com 2.6.31.5-96.fc12.x86_64 #1 SMP Fri Oct 23 19:30:30 EDT 2009 x86_64
x86_64 x86_64 GNU/Linux

Below are the versions installed:
[root@mx3550 ~]# rpm -qa|grep libvirt
libvirt-client-0.7.1-13.fc12.x86_64
libvirt-debuginfo-0.7.1-13.fc12.x86_64
libvirt-devel-0.7.1-13.fc12.x86_64
libvirt-python-0.7.1-13.fc12.x86_64
libvirt-0.7.1-13.fc12.x86_64

[root@mx3550 ~]# rpm -qa|grep kvm
qemu-kvm-0.11.0-9.fc12.x86_64

=Comment: #1=================================================
ANOOP C. VIJAYAN <email address hidden> -
The save hangs because the qemu process is not able to write to the file which libvirtd created.
This happens because qemu-kvm runs with uid of qemu user whereas libvirtd runs as a root user.
Moreover libvirtd creates the save file with only owner (root) read & write permissions.

[root@mx3550 ~]# tail /var/log/libvirt/qemu/rhel6.log
LC_ALL=C PATH=/sbin:/usr/sbin:/bin:/usr/bin HOME=/root USER=root LOGNAME=root QEMU_AUDIO_DRV=none
/usr/bin/qemu-kvm -S -M pc-0.11 -m 500 -smp 1 -name rhel6 -uuid 47b90387-e42a-d493-f037-0425f580cb9d
-monitor unix:/var/lib/libvirt/qemu/rhel6.monitor,server,nowait -boot c -drive
file=/var/lib/libvirt/images/rhel6.raw,if=ide,index=0,boot=on,format=raw -drive
file=,if=ide,media=cdrom,index=2 -net nic,macaddr=52:54:00:39:3f:5c,vlan=0,name=nic.0 -net
tap,fd=17,vlan=0,name=tap.0 -serial pty -parallel none -usb -vnc 127.0.0.1:0 -vga cirrus
char device redirected to /dev/pts/1
sh: /home/newguest: Permission denied <=======

[root@mx3550 ~]# ls -l /home/newguest
-rw------- 1 root root 1468 2009-11-03 15:59 /home/newguest

[root@mx3550 ~]# ps -eaf|grep qemu
qemu 4616 1 71 15:56 ? 00:00:28 /usr/bin/qemu-kvm -S -M pc-0.11 -m 500 -smp 1 -name
rhel6 -uuid 47b90387-e42a-d493-f037-0425f580cb9d -monitor
unix:/var/lib/libvirt/qemu/rhel6.monitor,server,nowait -boot c -drive
file=/var/lib/libvirt/images/rhel6.raw,if=ide,index=0,boot=on,format=raw -drive
file=,if=ide,media=cdrom,index=2 -net nic,macaddr=52:54:00:39:3f:5c,vlan=0,name=nic.0 -net
tap,fd=17,vlan=0,name=tap.0 -serial pty -parallel none -usb -vnc 127.0.0.1:0 -vga cirrus

[root@mx3550 ~]# ps -eaf|grep libvirtd
root 3800 1 0 15:32 ? 00:00:02 libvirtd --daemon

file: libvirt-0.7.1/src/qemu_driver.c
3803 static int qemudDomainSave(virDomainPtr dom,
3804 const char *path)
3805 {
------cut-----------
3874 /* Write header to file, followed by XML */
3875 if ((fd = open(path, O_CREAT|O_TRUNC|O_WRONLY, S_IRUSR|S_IWUSR)) < 0) {
3876 qemudReportError(dom->conn, dom, NULL, VIR_ERR_OPERATION_FAILED,
3877 _("failed to create '%s'"), path);