Re: [PATCH] cpu hotplug issue

Vasilis Liaskovitis
2011-08-02T09:46:03Z

Hi,

On Thu, Jul 28, 2011 at 6:52 PM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
> On 2011-07-27 18:35, Vasilis Liaskovitis wrote:
>> Hi,
>>
>> On Mon, Jul 25, 2011 at 3:18 PM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
>> Applying these 3 patches + hacks/fix on master doesn't solve the
>> initial "CPU: not responding" dmesg hotplug issue on my setup.
>> The ACPI event is delivered correctly, but "echo 1 >
>> /sys/devices/system/cpu/cpuX/online" still fails.
>> e.g. tested with "-smp 1,maxcpus=2"
>>
>> Could you share your qemu-kvm command line?
>
> Nothing special:
>
> qemu-system-x86_64 /my/image -m 1G -snapshot -smp 2,maxcpus=3 \
>        -cpu host,-kvmclock
>

ok, I have tested the patched qemu-kvm (guestOS ubuntu 10.10 with
2.6.35-24-generic kernel) with:

qemu-system-x86_64 /my/image -m 1G -smp 1,maxcpus=2 \
-cpu host,-kvmclock

on 2 different physical hosts. On the first one:

vendor_id : GenuineIntel
cpu family : 6
model : 37
model name : Intel(R) Core(TM) i3 CPU M 370 @ 2.40GHz

cpu hotplug works ok. When onlining (echo 1 >
/sys/devices/system/cpu/cpu1/online) dmesg shows:

Booting Node 0 Processor 1 APIC 0x1
TSC synchronization [CPU#0 -> CPU#1]:
Measured 3573498937792 cycles TSC warp between CPUs, turning off TSC clock.
Marking TSC unstable due to check_tsc_sync_source failed
kvm-clock: cpu 1, msr 0:1f15901, secondary cpu clock

on the second system:

vendor_id : AuthenticAMD
cpu family : 16
model : 4
model name : AMD Phenom(tm) II X4 955 Processor

onlining fails:

Booting Node 0 Processor 1 APIC 0x1
CPU1: Not Responding.

When I specify -kvmclock on the qemu command line for the AMD system,
it seems that the clocksource on the guest is hpet.
Dmesg on guest shows "Switching to clocksource hpet" and
/sys/devices/system/clocksource/clocksource0/current_clocksource
confirms.

When I don't specify -kvmclock, then the guest clocksource is actually
kvm-clock. But the onlining problem persists.

I have also tried a newer guestOS (debian-testing with 2.6.39 or 3.0.0
kernel) on the second system, same problem.

Also: what physical host have you used for testing?

thanks,

- Vasilis