During plugging we can see this event: echo 1 > cpu8/online.

But during unplugging , we can't see the event echo 0 > cpu8/online.

Just for additional check,  in my code  I have added following udev rule
echo 0 > cpu[0-9]*/online. May be this is of any help.

Thanks
Anshul Makkar

On Fri, Sep 12, 2014 at 11:53 AM, Gu Zheng <guz.fnst@cn.fujitsu.com> wrote:

> Hi Bharata,
> On 09/12/2014 04:09 PM, Bharata B Rao wrote:
>
> > On Fri, Sep 12, 2014 at 6:54 AM, Gu Zheng <guz.fnst@cn.fujitsu.com>
> wrote:
> >> Is guest os enabled acpi cpu hotplug? What's the guest's cpu info?
> >> Please try latest QEMU, and any feedback is welcome.
> >>
> >
> > Tried with latest QEMU git + your patchset and Fedora 20 guest, but
> > QEMU monitor still shows the removed CPU.
> >
> > Guest kernel messages during hotplug:
> >
> > [root@localhost cpu]# echo 1 > cpu8/online
> > [   72.936069] smpboot: Booting Node 0 Processor 8 APIC 0x8
> > [    0.003000] kvm-clock: cpu 8, msr 0:7ffc9201, secondary cpu clock
> > [   72.950003] TSC synchronization [CPU#0 -> CPU#8]:
> > [   72.950003] Measured 199886723309 cycles TSC warp between CPUs,
> > turning off TSC clock.
> > [   72.950003] tsc: Marking TSC unstable due to check_tsc_sync_source
> failed
> > [   72.972976] KVM setup async PF for cpu 8
> > [   72.973648] kvm-stealtime: cpu 8, msr 7d30df00
> > [   72.974415] Will online and init hotplugged CPU: 8
> > [   72.975307] microcode: CPU8 sig=0x663, pf=0x1, revision=0x1
> >
> > Guest kernel messages during hotunplug:
> >
> > [root@localhost cpu]# [   95.482172] Unregister pv shared memory for
> cpu 8
> > [   95.487169] smpboot: CPU 8 is now offline
> > [   95.488667] ACPI: Device does not support D3cold
> >
> >
> > Guest cpuinfo (showing for the last CPU only after adding and removing
> CPU 8)
> >
> > processor    : 7
> > vendor_id    : GenuineIntel
> > cpu family    : 6
> > model        : 6
> > model name    : QEMU Virtual CPU version 2.1.50
> > stepping    : 3
> > microcode    : 0x1
> > cpu MHz        : 2899.998
> > cache size    : 4096 KB
> > fpu        : yes
> > fpu_exception    : yes
> > cpuid level    : 4
> > wp        : yes
> > flags        : fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca
> > cmov pse36 clflush mmx fxsr sse sse2 syscall nx lm rep_good nopl pni
> > cx16 x2apic popcnt hypervisor lahf_lm
> > bogomips    : 5799.99
> > clflush size    : 64
> > cache_alignment    : 64
> > address sizes    : 40 bits physical, 48 bits virtual
> > power management:
>
> Guest ejected CPU 8 successfully.
> I confirmed it with the same environment as yours, it works well.
> Could you please offer your QEMU config and the guest start cmd?
> It may help me to investigate the issue.
>
> Thanks,
> Gu
>
> >
> > [root@localhost boot]# grep -ir hot config-3.11.10-301.fc20.x86_64
> > CONFIG_TICK_ONESHOT=y
> > # CONFIG_MEMORY_HOTPLUG is not set
> > CONFIG_HOTPLUG_CPU=y
> > # CONFIG_BOOTPARAM_HOTPLUG_CPU0 is not set
> > # CONFIG_DEBUG_HOTPLUG_CPU0 is not set
> > CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG=y
> > CONFIG_ACPI_HOTPLUG_CPU=y
> > CONFIG_HOTPLUG_PCI_PCIE=y
> > CONFIG_HOTPLUG_PCI=y
> > CONFIG_HOTPLUG_PCI_ACPI=y
> > CONFIG_HOTPLUG_PCI_ACPI_IBM=m
> > # CONFIG_HOTPLUG_PCI_CPCI is not set
> > CONFIG_HOTPLUG_PCI_SHPC=m
> > .
> >
>
>
>