Re: [Qemu-devel] Providing a mechanism to reopen() file based chardevs

[Daniel P. Berrange]

On Sat, Dec 06, 2014 at 08:35:19AM +1100, Tony Breeds wrote:
> Hi All,
>     Openstcak (Nova) has had an issue for a longish time where a running
> instance (qemu via libvirt) which has a file based console can fill the disk 
> of
> the hypervisor causing all guests to stall.
> 
> I'm looking at ways to fix this.  Clearly it can be done in openstack wothout
> changing qemu but it seems to be that a better idea would be to teach qemu to
> reopen() these files when it recieves a sighup and/or something in the 
> monitor.

My long term desired approach to deal with this problem in OpenStack (and
other libvirt based mgmt apps) is to have a separate log daemon in libvirt
eg a virtlogd daemon. Take QEMU out of the business of writing to files
entirely and instead it would always just be a given a pipe FD which is
connected to the daemon. This avoidis the need to give QEMU permission to
open files at all, which is inline with our general security strategy for
host resources QEMU accesses.

Regards,
Daniel
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