It was introduced by commit 7a51d9ebb, which started to use monitor commands without job acquiring, which is unsafe and leads to simultaneous access to vm->mon structure by different threads. Crash backtrace is the following (shortened): Program received signal SIGSEGV, Segmentation fault. qemuMonitorSend (mon=mon@entry=0x7f4ef4000d20, msg=msg@entry=0x7f4f18e78640) at qemu/qemu_monitor.c:1011 1011 while (!mon->msg->finished) { 0 qemuMonitorSend () at qemu/qemu_monitor.c:1011 1 0x00007f691abdc720 in qemuMonitorJSONCommandWithFd () at qemu/qemu_monitor_json.c:298 2 0x00007f691abde64a in qemuMonitorJSONCommand at qemu/qemu_monitor_json.c:328 3 qemuMonitorJSONQueryCPUs at qemu/qemu_monitor_json.c:1408 4 0x00007f691abcaebd in qemuMonitorGetCPUInfo g@entry=false) at qemu/qemu_monitor.c:1931 5 0x00007f691ab96863 in qemuDomainRefreshVcpuHalted at qemu/qemu_domain.c:6309 6 0x00007f691ac0af99 in qemuDomainGetStatsVcpu at qemu/qemu_driver.c:18945 7 0x00007f691abef921 in qemuDomainGetStats at qemu/qemu_driver.c:19469 8 qemuConnectGetAllDomainStats at qemu/qemu_driver.c:19559 9 0x00007f693382e806 in virConnectGetAllDomainStats at libvirt-domain.c:11546 10 0x00007f6934470c40 in remoteDispatchConnectGetAllDomainStats at remote.c:6267 (gdb) p mon->msg $1 = (qemuMonitorMessagePtr) 0x0 This change fixes it by calling qemuDomainRefreshVcpuHalted only when job is acquired. Signed-off-by: Maxim Nestratov <mnestratov(a)virtuozzo.com&gt; --- v1-v2: don't output halted cpu info if it wasn't rathered v2-v3: syntax-check recommendation src/qemu/qemu_driver.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index a82e58b..05a88c2 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -18978,7 +18978,7 @@ qemuDomainGetStatsVcpu(virQEMUDriverPtr driver, virDomainObjPtr dom, virDomainStatsRecordPtr record, int *maxparams, - unsigned int privflags ATTRIBUTE_UNUSED) + unsigned int privflags) { size_t i; int ret = -1; @@ -19005,10 +19005,16 @@ qemuDomainGetStatsVcpu(virQEMUDriverPtr driver, VIR_ALLOC_N(cpuwait, virDomainDefGetVcpus(dom->def)) < 0) goto cleanup; - if (qemuDomainRefreshVcpuHalted(driver, dom, - QEMU_ASYNC_JOB_NONE) == 0 && - VIR_ALLOC_N(cpuhalted, virDomainDefGetVcpus(dom->def)) < 0) - goto cleanup; + if (HAVE_JOB(privflags) && virDomainObjIsActive(dom)) { + if (qemuDomainRefreshVcpuHalted(driver, dom, + QEMU_ASYNC_JOB_NONE) < 0) { + /* it's ok to be silent and go ahead, because halted vcpu info + * wasn't here from the beginning */ + virResetLastError(); + } else if (VIR_ALLOC_N(cpuhalted, virDomainDefGetVcpus(dom->def)) < 0) { + goto cleanup; + } + } if (qemuDomainHelperGetVcpus(dom, cpuinfo, cpuwait, virDomainDefGetVcpus(dom->def), @@ -19462,7 +19468,7 @@ static struct qemuDomainGetStatsWorker qemuDomainGetStatsWorkers[] = { { qemuDomainGetStatsState, VIR_DOMAIN_STATS_STATE, false }, { qemuDomainGetStatsCpu, VIR_DOMAIN_STATS_CPU_TOTAL, false }, { qemuDomainGetStatsBalloon, VIR_DOMAIN_STATS_BALLOON, true }, - { qemuDomainGetStatsVcpu, VIR_DOMAIN_STATS_VCPU, false }, + { qemuDomainGetStatsVcpu, VIR_DOMAIN_STATS_VCPU, true }, { qemuDomainGetStatsInterface, VIR_DOMAIN_STATS_INTERFACE, false }, { qemuDomainGetStatsBlock, VIR_DOMAIN_STATS_BLOCK, true }, { qemuDomainGetStatsPerf, VIR_DOMAIN_STATS_PERF, false }, -- 2.4.11