[libvirt] [PATCH] qemu: turn on virtlockd by default

[Ján Tomko]

On Fri, Jan 22, 2016 at 03:56:08PM +0000, Daniel P. Berrange wrote:
> We have had virtlockd available for a long time now but
> have always defaulted to the 'nop' lock driver which does
> no locking. This gives users an unsafe deployment by
> default unless they know to turn on lockd.

Does the default setup of virtlockd offer any safety?

After looking at:
https://bugzilla.redhat.com/show_bug.cgi?id=1191802
It seems that with dynamic_ownership enabled we first apply
the security labels, then check the disk locks by calling
virDomainLockProcessResume right before starting the CPUs
in virDomainLockProcessResume. After that fails, resetting
the uid:gid back to root:root cuts off the access to the disk
for the already running domain.

Is there a reason why the locks are checked so late?

I assume this only ever worked for the case of migration with
shared storage (and shared lockspace).

Jan
> virtlockd will
> auto-activate via systemd when guests launch, so setting
> it on by default will only cause upgrade pain for people
> on non-systemd distros.
> 
> Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
> ---
>  src/qemu/qemu.conf     | 3 ++-
>  src/qemu/qemu_driver.c | 2 +-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
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