[libvirt] Problem in handling fast prints from QEMU to stderr

[Saul Tamari]

Hi,

I think I spotted a bug in the way libvirtd handles stderr output from QEMU VMs.

When starting a VM and QEMU outputs too much output data to stderr
(during a given time period), libvirtd will fail and report the
following error to /var/log/messages:
libvirtd: 13:44:40.695: error : internal error Out of space while
reading console log output

I looked at the libvirt code a bit and it seems like the
stderr-handling code (I think its in qemudReadLogOutput()) is
time-dependent and if a 4K buffer overflows it will stop running this
VM.
As a workaround I added some usleep(250000) near the fprintf() calls
(inside QEMU) and I now manage to get the VM running.

Is this the way libvirtd is supposed to behave?


Thanks,
Saul

p.s. This was tested on FC11 and libvirtd is version 0.6.2