On 2011-07-21 13:51, Gleb Natapov wrote: > On Thu, Jul 21, 2011 at 01:42:08PM +0200, Jan Kiszka wrote: >> 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. >> > CPU hotplug for Linux suppose to be easy (with allow_hotplug patch > applied). But we have two bugs currently. One is that ACPI interrupt I bet we have multiple bugs for quite a while now, which accelerated bit rotting even further. > is not send when cpu is onlined (at least this appears to be the case). > I will look at that one. Another is that after new cpu is detected it > can't be onlined. > > After fixing the first bug the test should look like this: > 1. start vm with -smp 1,macpus=2 > 2. wait for it to boot > 3. do "cpu 1 online" in monitor. > 4. do "echo 1 > /sys/devices/system/cpu/cpu1/online" > > If step 4 should succeed. It fails now. Should the above work even with the current ACPI issue unfixed? 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
