On Mon, Jul 25, 2011 at 03:18:19PM +0200, Jan Kiszka wrote: > On 2011-07-24 18:11, Jan Kiszka wrote: > >>> I had a closer look and identified two further issues, one generic, one > >>> CPU-hotplug-specific: > >>> - (qdev) devices that are hotplugged do not receive any reset. That > >>> does not only apply to the APIC in case of CPU hotplugging, it is > >>> also broken for NICs, storage controllers, etc. when doing PCI > >>> hot-add as I just checked via gdb. > >>> - CPU hotplugging was always (or at least for a fairly long time), > >>> well, fragile as it failed to make CPU thread creation and CPU > >>> initialization atomic against APIC addition and other initialization > >>> steps. IOW, we need to create CPUs stopped, finish all init work, > >>> sync their states completely to the kernel > >>> (cpu_synchronize_post_init), and then kick them of. Actually I'm > >> Syncing the state to the kernel should be done by vcpu thread, so I it > >> cannot be stopped while the sync is done. May be I misunderstood what > >> you mean here. > > > > Stopped first of all means not entering kvm_cpu_exec before the whole > > setup and the initial sync are done. > > > > Syncing the initial state may also happen over the creating context as > > long as the vcpus are stopped (analogously to > > kvm_cpu_synchronize_post_init). > > OK, hacks below plus the following three patches make CPU hotplug work > again - with some exceptions. Here are the patches: > > 1. http://thread.gmane.org/gmane.comp.emulators.kvm.devel/76484 > 2. http://thread.gmane.org/gmane.comp.emulators.qemu/110272 > 3. http://thread.gmane.org/gmane.comp.emulators.qemu/110426 > > And here are the hacks (well, the first hunk is clearly a fix, the last > one clearly a hack, /me still undecided about the rest): > > diff --git a/hw/acpi_piix4.c b/hw/acpi_piix4.c > index c30a050..f650250 100644 > --- a/hw/acpi_piix4.c > +++ b/hw/acpi_piix4.c > @@ -92,7 +92,8 @@ static void pm_update_sci(PIIX4PMState *s) > ACPI_BITMASK_POWER_BUTTON_ENABLE | > ACPI_BITMASK_GLOBAL_LOCK_ENABLE | > ACPI_BITMASK_TIMER_ENABLE)) != 0) || > - (((s->gpe.sts[0] & s->gpe.en[0]) & PIIX4_PCI_HOTPLUG_STATUS) != 0); > + (((s->gpe.sts[0] & s->gpe.en[0]) & > + (PIIX4_PCI_HOTPLUG_STATUS | PIIX4_CPU_HOTPLUG_STATUS)) != 0); > > qemu_set_irq(s->irq, sci_level); > /* schedule a timer interruption if needed */ > diff --git a/hw/pc.c b/hw/pc.c > index c0a88e1..e5371be 100644 > --- a/hw/pc.c > +++ b/hw/pc.c > @@ -42,6 +42,7 @@ > #include "kvm.h" > #include "blockdev.h" > #include "ui/qemu-spice.h" > +#include "cpus.h" > > /* output Bochs bios info messages */ > //#define DEBUG_BIOS > @@ -936,6 +937,10 @@ CPUState *pc_new_cpu(const char *cpu_model) > #endif > } > > + if (vm_running) { > + pause_all_vcpus(); > + } > + > env = cpu_init(cpu_model); > if (!env) { > fprintf(stderr, "Unable to find x86 CPU definition\n"); > @@ -947,6 +952,11 @@ CPUState *pc_new_cpu(const char *cpu_model) > } > qemu_register_reset(pc_cpu_reset, env); > pc_cpu_reset(env); > + > + cpu_synchronize_post_init(env); > + if (vm_running) { > + resume_all_vcpus(); > + } > return env; > } > > diff --git a/hw/qdev.c b/hw/qdev.c > index 1626131..b91e2c2 100644 > --- a/hw/qdev.c > +++ b/hw/qdev.c > @@ -330,6 +330,7 @@ BusState *sysbus_get_default(void) > if (!main_system_bus) { > main_system_bus = qbus_create(&system_bus_info, NULL, > "main-system-bus"); > + main_system_bus->allow_hotplug = 1; > } > return main_system_bus; > } > > I see two remaining problems: > - kvmclock is somehow broken, either in my guest kernel (OpenSUSE HEAD > 3.0.0-2) or the host, -cpu host,-kvmclock works around sporadic > guest lockups on echo 1 > /sys... > - Seabios tends to lock up once every few system_reset after some > CPU has been hot-added - also in TCG mode. It seems to dislike any > setup of #CPUs > smp_cpus (whatever that implies in details). > Have you specified maxcpus? Something like -smp 1,maxcpus=4. -- Gleb. -- 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
