Re: qemu modularization of qemu-5.1 vs libvirt domcapabilities cache?

On 8/20/20 8:56 AM, Jim Fehlig wrote: > On 8/20/20 6:54 AM, Christian Ehrhardt wrote: > > On Thu, Aug 20, 2020 at 12:43 PM Martin Wilck <mwilck(a)suse.com&gt; wrote: > > > > > > On Thu, 2020-08-20 at 11:00 +0100, Daniel P. Berrangé wrote: > > > > On Wed, Aug 05, 2020 at 10:19:26AM +0200, Andrea Bolognani wrote: > > > > > contents change. > > > > > > > > > > That said, if upgrading QEMU results in losing features, even > > > > > though > > > > > you can recover them through additional steps I would argue that's > > > > > a > > > > > bug in the packaging that should be addressed on the QEMU side. > > > > > > > > Potentially we can consider this a  distro packaging problem and fix > > > > it at the RPM level. > > > > > > > > eg the libvirt RPM can define a trigger that runs when *any* of the > > > > qemu-device*  RPMs is installed/updated. This trigger can simply > > > > touch a file on disk somewhere, and libvirtd can monitor this one > > > > file, instead of having to monitor every module. > > > > > > The simplest approach is to touch the qemu binaries. We discussed this > > > already. It has the drawback that it makes "rpm -V" complain about > > > wrong timestamps. It might also confuse backup software. Still, it > > > might be a viable short-term workaround if nothing else is available. > > > > Qemu already allows to save modules in /var/run/qemu/ [1] to better handle > > module upgrades which is already used in Debian and Ubuntu to avoid > > late module load errors after upgrades. > > > > This was meant for upgrades, but if libvirt would define a known path in > > there like /var/run/qemu/last_packaging_change the packages could easily > > touch it on any install/remove/update as Daniel suggested and libvirt could > > check this path like it does with the date of the qemu binary already. > > That would require changes in libvirt and the various module packages > right? Are you fine with Daniel's suggestion of handling this all within > libvirt? E.g. on the packaging side libvirt could define a trigger to be > notified when the modules dir is updated and touch a well-known file > > %filetriggerin -- %{_libdir}/qemu > touch /var/cache/libvirt/qemu/capabilities/module-changed > %filetriggerun -- %{_libdir}/qemu > touch /var/cache/libvirt/qemu/capabilities/module-changed Hmm, this is still problematic for session mode. I think your suggestion covers both system and session modes nicely.