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Date: Mon, 8 Dec 2014 18:12:11 +0800
From: Gu Zheng <guz.fnst@cn.fujitsu.com>
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Subject: Re: [Qemu-devel] [RFC V2 10/10] cpus: reclaim allocated vCPU objects
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To: Bharata B Rao <bharata.rao@gmail.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, tangchen@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, Anshul Makkar <anshul.makkar@profitbricks.com>, ChenFan <chen.fan.fnst@cn.fujitsu.com>, Igor Mammedov <imammedo@redhat.com>, "afaerber@suse.de" <afaerber@suse.de>

Hi Bharata,
On 12/08/2014 05:16 PM, Bharata B Rao wrote:

> On Thu, Aug 28, 2014 at 9:06 AM, Gu Zheng <guz.fnst@cn.fujitsu.com> wrote=
:
>> After ACPI get a signal to eject a vCPU, the vCPU must be
>> removed from CPU list=EF=BC=8Cbefore the vCPU really removed,  then
>> release the all related vCPU objects.
>> But we do not close KVM vcpu fd, just record it into a list, in
>> order to reuse it.
>=20
> Hi Gu Zheng,
>=20
> So this approach of parking the vcpu fd in QEMU and reusing it next
> time during CPU hotplug will only work if all architectures supported
> by KVM driver are ok with reuse of vcpu object in the kernel. I am
> using relevant bits of this patch of yours with PowerPC architecture
> to support cpu unplug and I realize that there is at least one case
> where reuse of vcpu object in the kernel causes problems. Before I
> attempt to fix that in ppc KVM, I wanted to check if there is
> consensus on this approach (parking and reusing kvm vcpu fd) in QEMU.

Not yet, also no objection.
But it's the best way that I can find to handle the vcpu object without
touching the CPU array in kernel.

>=20
> Also is there a latest version of this patchset that I can try ?

A new version is on the respinning, and will be sent out once the 2.2 relea=
sed.

Thanks,
Gu

>=20
> Regards,
> Bharata.
> .
>=20