From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH 2/2] kvm: exit to userspace with reason
 KVM_EXIT_VCPU_DEAD
Date: Sun, 27 Nov 2011 12:50:00 +0200
Message-ID: <20111127105000.GL2557@redhat.com>
References: <1322188529-11609-1-git-send-email-kernelfans@gmail.com>
	<1322361735-21428-1-git-send-email-kernelfans@gmail.com>
	<4ED212C7.1080901@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: aliguori@us.ibm.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Liu Ping Fan <kernelfans@gmail.com>, qemu-devel@nongnu.org,
	ryanh@us.ibm.com, jan.kiszka@web.de
To: Avi Kivity <avi@redhat.com>
Return-path: <qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org>
Content-Disposition: inline
In-Reply-To: <4ED212C7.1080901@redhat.com>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org
Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org
List-Id: kvm.vger.kernel.org

On Sun, Nov 27, 2011 at 12:36:55PM +0200, Avi Kivity wrote:
> On 11/27/2011 04:42 AM, Liu Ping Fan wrote:
> > From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> >
> > The vcpu can be safely released when
> > --1.guest tells us that the vcpu is not needed any longer.
> > --2.vcpu hits the last instruction _halt_
> >
> > If both of the conditions are satisfied, kvm exits to userspace
> > with the reason vcpu dead. So the user thread can exit safely.
> >
> >
> 
> Seems to be completely unnecessary.  If you want to exit from the vcpu
> thread, send it a signal.
> 
Also if guest "tells us that the vcpu is not needed any longer" (via
ACPI I presume) and vcpu actually doing something critical instead of
sitting in 1:hlt; jmp 1b loop then it is guest's problem if it stops
working after vcpu destruction.

--
			Gleb.