[libvirt] [PATCH] qemu: Always refresh capabilities if no <guests> found (bz 1000116)

[Michal Privoznik]

On 16.04.2015 21:08, Cole Robinson wrote:
> - Remove all qemu emulators
> - Restart libvirtd
> - Install qemu emulators
> - Call 'virsh version' -> errors
> 
> The only thing that will force the qemu driver to refresh it's cached
> capablities info is an explict API call to GetCapabilities.
> 
> However in the case when the initial caps lookup at driver connect didn't
> find a single qemu emulator to poll, the driver is effectively useless
> and really can't do anything until it's populated some qemu capabilities
> info.
> 
> With the above steps, the user would have to either know about the
> magic refresh capabilities call, or restart libvirtd to pick up the
> changes.
> 
> Instead, this patch changes things so that every time a part of th
> driver requests access to capabilities info, check to see if
> we've previously seen any emulators. If not, force a refresh.
> 
> In the case of 'still no emulators found', this is still very quick, so
> I can't think of a downside.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=1000116
> ---
>  src/qemu/qemu_conf.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
> index 2cf3905..b662b69 100644
> --- a/src/qemu/qemu_conf.c
> +++ b/src/qemu/qemu_conf.c
> @@ -965,6 +965,13 @@ virCapsPtr virQEMUDriverGetCapabilities(virQEMUDriverPtr driver,
>          qemuDriverLock(driver);
>      }
>  
> +    if (driver->caps->nguests == 0 && !refresh) {
> +        VIR_DEBUG("Capabilities didn't detect any guests. Forcing a "
> +            "refresh.");
> +        qemuDriverUnlock(driver);
> +        return virQEMUDriverGetCapabilities(driver, true);
> +    }
> +
>      ret = virObjectRef(driver->caps);
>      qemuDriverUnlock(driver);
>      return ret;
> 

ACK, although I'd remove "(bz ...)" from the $subj and keep the BZ link
in the commit message.

Michal