linux-kernel - Re: [PATCH 0] A series patches for kvm&qemu to enable vcpu destruction in kvm

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Message-ID: <4ECFD645.2060201@web.de>
Date:	Fri, 25 Nov 2011 15:54:13 -0200
From:	Jan Kiszka <jan.kiszka@....de>
To:	Liu Ping Fan <kernelfans@...il.com>
CC:	kvm@...r.kernel.org, qemu-devel@...gnu.org,
	linux-kernel@...r.kernel.org, avi@...hat.com, aliguori@...ibm.com,
	ryanh@...ibm.com
Subject: Re: [PATCH 0] A series patches for kvm&qemu to enable vcpu destruction
 in kvm

On 2011-11-25 00:35, Liu Ping Fan wrote:
> A series of patches from kvm, qemu to guest. These patches will finally enable vcpu destruction in kvm instance and let vcpu thread exit in qemu.
>  
> Currently, the vcpu online feature enables the dynamical creation of vcpu and vcpu thread, while the offline feature can not destruct the vcpu and let vcpu thread exit, it just halt in kvm. Because currently, the vcpu will only be destructed when kvm instance is destroyed. We can 
> change vcpu as an refer of kvm instance, and then vcpu's destruction MUST and CAN come before kvm's destruction.
> 
> These patches use guest driver to notify the CPU_DEAD event to qemu, and later qemu asks kvm to release the dead vcpu and finally exit the 
> thread. 
> The usage is: 
> 	qemu$cpu_set n online
> 	qemu$cpu_set n zap   ------------ This will destroy the vcpu-n in kvm and let vcpu thread exit
>      OR	
> 	qemu$cpu_set n offline 	--------- This will just block vcpu-n in kvm
> 
> Any comment and suggestion are welcome.

The cpu_set command will probably not make it to QEMU upstream
(device_add/delete is the way to go - IMHO). So I would refrain from
adding anything to qemu-kvm at this point anyway. Also, what would be
the advantage of 'zap' from user perspective?

> 
> 
> Patches include:
> |-- guest
> |   `-- 0001-virtio-add-a-pci-driver-to-notify-host-the-CPU_DEAD-.patch
> |-- kvm
> |   |-- 0001-kvm-make-vcpu-life-cycle-separated-from-kvm-instance.patch
> |   `-- 0002-kvm-exit-to-userspace-with-reason-KVM_EXIT_VCPU_DEAD.patch
> `-- qemu
>     |-- 0001-Add-cpu_phyid_to_cpu-to-map-cpu-phyid-to-CPUState.patch
>     |-- 0002-Add-cpu_free-to-support-arch-related-CPUState-releas.patch
>     |-- 0003-Introduce-a-pci-device-cpustate-to-get-CPU_DEAD-even.patch
>     |-- 0004-Release-vcpu-and-finally-exit-vcpu-thread-safely.patch
>     `-- 0005-tmp-patches-for-linux-header-files.patch
> 

I only found kvm patch 0001 so far. Something probably went wrong with
your postings.

Jan


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