On 28/03/2017 13:46, Josh Poimboeuf wrote: > On Tue, Mar 28, 2017 at 03:51:01AM -0400, Paolo Bonzini wrote: >> >>> While debugging a kernel issue, I found that QEMU always reboots when an >>> x86 triple fault occurs, which complicates debugging. QEMU and libvirt >>> have a facility for creating a dump when KVM reports >>> KVM_SYSTEM_EVENT_CRASH. So change the VMX triple fault handler to do >>> that. This gives user space the ability to decide whether to dump, >>> pause, shutdown, or reboot. >> >> You probably want QEMU's -no-reboot option. >> >> Triple faults are already reported to userspace with KVM_EXIT_SHUTDOWN, >> and it's up to userspace to decide what to do with it. This patch cannot >> be applied, because there are guests that do a triple-fault intentionally >> in order to reset the machine. > > Ok. Any idea how to force libvirt to create a dump? It has a > 'coredump-destroy' option, but that only seems to work with 'on_crash': > > https://libvirt.org/formatdomain.html#elementsEvents Probably QEMU, when invoked with -no-shutdown -no-reboot, should treat KVM_EXIT_SHUTDOWN as a panic. I can have a go at it, but note that QEMU is now in hard freeze for the next release, so it will take a while. However you're using libvirt and it doesn't use -no-reboot. It's probably possible for libvirt to use -no-reboot more often. The price would be that if libvirtd crashes and a VM wants to reset, then the VM gets stuck. Alternatively, we could generalize -no-shutdown and -no-reboot to something like: -action reset=stop|restart|quit, poweroff=stop|quit, triple-fault=stop|panic|restart|quit and teach libvirt about it. The current semantics map relatively easily to the new option: | reset | poweroff | triple-fault --------------------------+-------------+------------+------------------- no option | restart | quit | restart -no-shutdown | restart | stop | restart -no-reboot | quit | quit | quit -no-shutdown -no-reboot | stop | stop | stop (panic?) Paolo
