On 2011-07-21 13:33, Gleb Natapov wrote: > On Thu, Jul 21, 2011 at 01:06:41PM +0200, Vasilis Liaskovitis wrote: >> Hi, >> >> On Wed, Jul 20, 2011 at 10:35 AM, Gleb Natapov <gleb@xxxxxxxxxx> wrote: >>> On Tue, Jul 19, 2011 at 07:40:55PM +0200, Vasilis Liaskovitis wrote: >>>> Hello, >>>> >>>> I have encountered a problem trying to hotplug a CPU in my x86_64 guest setup. >>>> >>> You do everything right. It's qemu who is buggy. Since qemu need a patch >>> for cpu hotplug to not crash it nobody tests it, so code bit rots. >> >> thanks for your reply. >> >> As I mentioned in the original email, onlining a hotplugged-cpu with >> qemu-kvm/master results in: >> >>>> echo 1 > /sys/devices/system/cpu/cpu1/online >>>> bash: echo: write error: Input/output error >>>> >>>> in the guest, dmesg reports: >>>> >>>> [ 2325.376355] Booting Node 0 Processor 1 APIC 0x1 >>>> [ 2325.376357] smpboot cpu 1: start_ip = 9a000 >>>> [ 2330.821306] CPU1: Not responding. >> >> I tried to git-bisect between qemu-kvm-0.13.0 (last known version >> where cpu hotplug works correctly >> for me) and qemu-kvm/master. >> >> More precisely: To enable cpu-hotplug at each bisect stage, I apply >> this patch derived from: >> http://lists.gnu.org/archive/html/qemu-devel/2010-08/msg00850.html >> >> diff --git a/hw/qdev.c b/hw/qdev.c >> index 1aa1ea0..aed48ce 100644 >> --- a/hw/qdev.c >> +++ b/hw/qdev.c >> @@ -327,6 +327,7 @@ 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; >> } >> >> and test cpu hotplug functionality. >> The commit that appears to break CPU hotplug is: >> > Thank you for going through the pain of bisecting it! Bisects that > require patch to be applied between each step are especially annoying. > >> commit f4de8c1451f2265148ff4d895a27e21c0a8788aa >> Author: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> >> Date: Mon Feb 21 12:28:07 2011 +0100 >> qemu-kvm: Mark VCPU state dirty on creation >> > Jan can you look at this please? I can't promise to do debugging myself. Also, as I never succeeded in getting anything working with CPU hotplug, even back in the days it was supposed to work, I'm a bit clueless /wrt to the right test cases. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- 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
