Re: [libvirt] [PATCH 4/4] qemu: Wire up better early error reporting

The previous patches added infrastructure to report better errors from monitor in some cases. This patch finalizes this "feature" by enabling this enhanced error reporting on early phases of VM startup. In these phases the possibility of qemu producing a useful error message is really high compared to running it during the whole life cycle. After the start up is complete, the feature is disabled to provide the usual error messages so that users are not confused by possibly irrelevant messages that may be in the domain log. The original motivation to do this enhancement is to capture errors when using VFIO device passthrough, where qemu reports errors after the monitor is initialized and the existing error catching code couldn't catch this producing a unhelpful message: # virsh start test error: Failed to start domain test error: Unable to read from monitor: Connection reset by peer With this change, the message is changed to: # virsh start test error: Failed to start domain test error: internal error: early end of file from monitor: possible problem: qemu-system-x86_64: -device vfio-pci,host=00:1a.0,id=hostdev0,bus=pci.0,addr=0x5: vfio: error, group 8 is not viable, please ensure all devices within the iommu_group are bound to their vfio bus driver. qemu-system-x86_64: -device vfio-pci,host=00:1a.0,id=hostdev0,bus=pci.0,addr=0x5: vfio: failed to get group 8 qemu-system-x86_64: -device vfio-pci,host=00:1a.0,id=hostdev0,bus=pci.0,addr=0x5: Device 'vfio-pci' could not be initialized --- src/qemu/qemu_process.c | 30 +++++++++++++++++++----------- 1 file changed, 19 insertions(+), 11 deletions(-) diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c index 846cee6..43b5c2b 100644 --- a/src/qemu/qemu_process.c +++ b/src/qemu/qemu_process.c @@ -1389,7 +1389,7 @@ static qemuMonitorCallbacks monitorCallbacks = { }; static int -qemuConnectMonitor(virQEMUDriverPtr driver, virDomainObjPtr vm) +qemuConnectMonitor(virQEMUDriverPtr driver, virDomainObjPtr vm, int logfd) { qemuDomainObjPrivatePtr priv = vm->privateData; int ret = -1; @@ -1415,6 +1415,9 @@ qemuConnectMonitor(virQEMUDriverPtr driver, virDomainObjPtr vm) &monitorCallbacks, driver); + if (mon && qemuMonitorSetDomainLog(mon, logfd) < 0) + goto error; + virObjectLock(vm); priv->monStart = 0;