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Date: Mon, 28 Jul 2014 16:19:35 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH/RFC 4/5] s390x/kvm: test whether a cpu is
 STOPPED when checking "has_work"
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To: David Hildenbrand <dahi@linux.vnet.ibm.com>, Alexander Graf <agraf@suse.de>
Cc: linux-s390 <linux-s390@vger.kernel.org>, KVM <kvm@vger.kernel.org>, qemu-devel <qemu-devel@nongnu.org>, Christian Borntraeger <borntraeger@de.ibm.com>, Jens Freimann <jfrei@linux.vnet.ibm.com>, Cornelia Huck <cornelia.huck@de.ibm.com>

Il 28/07/2014 16:16, David Hildenbrand ha scritto:
> Later, another vcpu might decide to turn that vcpu back on (by e.g. sending a
> SIGP START to that vcpu).
> 
> I am not sure if such a mechanism/scenario is applicable to any other arch. They
> all seem to reset the cs->halted flag if they know they are able to run (e.g.
> due to an interrupt) - they have no such thing as "stopped cpus", only
> "halted/waiting cpus".

On x86, INIT_RECEIVED is pretty much a stopped CPU.  It can only run
(and receive interrupts) after getting a special startup interrupt ("SIPI").

Paolo