Re: [libvirt] QMP Capability Detection Issues with GIT version of QEMU

I ran into trouble today trying to use the GIT level of QEMU. In a nutshell: the capability detection with QMP is failing and the fallback using -help isn't working with the GIT level probably due to help text reformatting. The failure reason is that QEMU cannot bind to the QMP monitor socket in the /var/lib/libvirt/qemu directory. That's because the child process is stripped of all capabilities and this directory is chown'ed to qemu:qemu by the QEMU driver. Note that this is failing with the release QEMU as well, with the difference that the fallback is working there. I am willing to provide a patch, however I'd like to get feedback on the approach to use: 1. Add back Linux capabilities CAP_DAC_OVERRIDE, CAP_DAC_READ_SEARCH to allow QEMU to bind to the monitor socket. This seems to be hacky/dodging the problem. 2. Use a separate directory for the QMP probing instance of QEMU. 3. Run the QMP QEMU under the configured qemu user. This would be my favorite.