[libvirt] [PATCHv2 2/4] qemu: monitor: Add infrastructure to access VM logs for better err msgs

Early VM startup errors usually produce a better error message in the machine log file. Currently we were accessing it only when the process exited during certain phases of startup. This will help adding a more comprehensive error extraction for early qemu startup phases. This patch adds infrastructure to keep a file descriptor for the machine log file that will be used in case an error happens. --- Notes: Version 2: - no changes, just explained motivation in reply to previous version src/qemu/qemu_monitor.c | 27 +++++++++++++++++++++++++++ src/qemu/qemu_monitor.h | 2 ++ 2 files changed, 29 insertions(+) diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c index ecec8e2..c3701fe 100644 --- a/src/qemu/qemu_monitor.c +++ b/src/qemu/qemu_monitor.c @@ -88,6 +88,9 @@ struct _qemuMonitor { /* If found, path to the virtio memballoon driver */ char *balloonpath; bool ballooninit; + + /* Log file fd of the qemu process to dig for usable info */ + int logfd; }; static virClassPtr qemuMonitorClass; @@ -254,6 +257,7 @@ static void qemuMonitorDispose(void *obj) VIR_FREE(mon->buffer); virJSONValueFree(mon->options); VIR_FREE(mon->balloonpath); + VIR_FORCE_CLOSE(mon->logfd); } @@ -715,6 +719,7 @@ qemuMonitorOpenInternal(virDomainObjPtr vm, return NULL; mon->fd = -1; + mon->logfd = -1; if (virCondInit(&mon->notify) < 0) { virReportError(VIR_ERR_INTERNAL_ERROR, "%s", _("cannot initialize monitor condition")); @@ -3843,3 +3848,25 @@ qemuMonitorGetDeviceAliases(qemuMonitorPtr mon, return qemuMonitorJSONGetDeviceAliases(mon, aliases); } + + +/** + * qemuMonitorSetDomainLog: + * Set the file descriptor of the open VM log file to report potential + * early startup errors of qemu. + * + * @mon: Monitor object to set the log file reading on + * @logfd: File descriptor of the already open log file + */ +int +qemuMonitorSetDomainLog(qemuMonitorPtr mon, int logfd) +{ + VIR_FORCE_CLOSE(mon->logfd); + if (logfd >= 0 && + (mon->logfd = dup(logfd)) < 0) { + virReportSystemError(errno, "%s", _("failed to duplicate log fd")); + return -1; + } + + return 0; +} diff --git a/src/qemu/qemu_monitor.h b/src/qemu/qemu_monitor.h index 5fe33db..06ba7e8 100644 --- a/src/qemu/qemu_monitor.h +++ b/src/qemu/qemu_monitor.h @@ -761,6 +761,8 @@ int qemuMonitorDetachCharDev(qemuMonitorPtr mon, int qemuMonitorGetDeviceAliases(qemuMonitorPtr mon, char ***aliases); +int qemuMonitorSetDomainLog(qemuMonitorPtr mon, int logfd); + /** * When running two dd process and using <> redirection, we need a * shell that will not truncate files. These two strings serve that -- 1.8.3.2