On Fri, Apr 17, 2009 at 10:53 AM, Marcelo Tosatti <mtosatti@xxxxxxxxxx> wrote: > Hi Glauber, > > On Fri, Apr 17, 2009 at 01:15:21AM -0400, Glauber Costa wrote: >> As KVM cpus runs on threads, it is possible that >> we call kvm_load_registers() from a cpu thread, while the >> apic has not yet fully initialized. kvm_load_registers() is called >> from ap_main_loop. >> >> This is not a problem when we're starting the whole machine together, >> but is a problem for hotplug, since we don't have the protection >> of the locks that protect machine initialization. Currently, some executions >> of cpu hotplug on rainy sundays fail with a segfault. > > /* and wait for machine initialization */ > while (!qemu_system_ready) > qemu_cond_wait(&qemu_system_cond); > pthread_mutex_unlock(&qemu_mutex); > > Shouldnt this cover the cpu hotplug case too? Perhaps have: > > /* wait for machine initialization */ > while (!qemu_system_ready) > qemu_cond_wait(&qemu_system_cond); > /* wait for vcpu initialization */ > while (!env->initialized) > qemu_cond_wait(&qemu_system_cond); > pthread_mutex_unlock(&qemu_mutex); > > And then set env->initialized when the cpu is good to go. >From my understanding, all this is only useful when the whole machine is starting, since they are global locks that wait for a system wide condition. This is not the case with cpu hotplug, since the box is already on. > > Because there could be other dependencies other than APIC > initialization, for eg in pc_new_cpu > > if (cpu != 0) > env->halted = 1; it is okay for the cpu to be halted. Btw, I believe this should be moved inside cpu init. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
