> -----Original Message----- > From: Daniel P. Berrangé <berrange@xxxxxxxxxx> > Sent: 01 March 2021 15:39 > To: Thanos Makatos <thanos.makatos@xxxxxxxxxxx> > Cc: libvir-list@xxxxxxxxxx > Subject: Re: using libvirt 4.5 with upstream qemu > > On Mon, Mar 01, 2021 at 03:30:58PM +0000, Thanos Makatos wrote: > > I'm trying to use QEMU master with libvirt 4.5 and QEMU seems to be > > hanging when I try to start a guest. > > > > My environment is a modified CentOS 7.9 installation using libvirt > > 4.5.0. When I use a modified version of QEMU 2.12 (reasonably close to > > the stock CentOS > > version) everything works fine. When I try to use a fairly recent > > version of QEMU (e.g. v5.2.0-729-g89ff714f4b). > > > > qemu 118657 1.6 0.0 0 0 ? Z 14:50 0:00 [qemu-kvm] > <defunct> > > qemu 118664 0.0 0.0 207340 3560 ? Ssl 14:50 0:00 > /usr/libexec/qemu-kvm -S -no-user-config -nodefaults -nographic -machine > none,accel=kvm:tcg -qmp > unix:/var/lib/libvirt/qemu/capabilities.monitor.sock,server,nowait -pidfile > /var/lib/libvirt/qemu/capabilities.pidfile -daemonize > > qemu 118666 0.0 0.0 275008 13916 ? Sl 14:50 0:00 > /usr/libexec/qemu-kvm -S -no-user-config -nodefaults -nographic -machine > none,accel=kvm:tcg -qmp > unix:/var/lib/libvirt/qemu/capabilities.monitor.sock,server,nowait -pidfile > /var/lib/libvirt/qemu/capabilities.pidfile -daemonize > > > > /var/lib/libvirt/qemu/capabilities.pidfile contains the PID of the 2nd > > QEMU process and by experimenting I found that by killing the QEMU > > process NOT in the PID file the same thing happens again (maybe once > > more or twice) and then the guest boots fine. > > > > Does libvirt have some specific QEMU dependency? Is there some > > compatibility matrix I might have missed? I understand this may not be > > a supported configuration given that I'm not using vanilla > > libvirt/QEMU, however I'd appreciate some pointers so I can further > > debug this. I've trying debugging this in case there's some obvious error but > didn't find anything interesting. > > You want libvirt to be the same age as the QEMU you're using, or newer. Makes sense, thanks. > > New libvirt is expected to work with old QEMU. > > Old libvirt may not work with new QEMU. > > QEMU's deprecation process leads to code/behaviour being > removed/changed over time and this may break old libvirt. I don't know the > cause of the problem in your specific case, but personally i wouldn't spend > time trying to debug it as it isn't a scenario we attempt to support.
