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Date: Fri, 16 Mar 2012 16:05:04 +0800
From: Wen Congyang <wency@cn.fujitsu.com>
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To: Avi Kivity <avi@redhat.com>
CC: Jan Kiszka <jan.kiszka@siemens.com>, Gleb Natapov <gleb@redhat.com>,
        Eric Northup <digitaleric@google.com>,
        "Daniel P. Berrange" <berrange@redhat.com>,
        kvm list <kvm@vger.kernel.org>, qemu-devel <qemu-devel@nongnu.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Amit Shah <amit.shah@redhat.com>
Subject: Re: [PATCH 0/2 v3] kvm: notify host when guest panicked
References: <4F60726E.3090807@cn.fujitsu.com> <4F607325.6050607@redhat.com> <20120314104608.GU2304@redhat.com> <4F607789.4010109@redhat.com> <4F607CE4.2060809@cn.fujitsu.com> <4F609822.7050502@redhat.com> <20120314131415.GB2304@redhat.com> <4F609A15.5020902@redhat.com> <20120314132552.GC2304@redhat.com> <CAG7+5M0gEpoJ_jnC8_4Ae-xe2rr7+CJLZh3JjAhh=p=-2bEAcA@mail.gmail.com> <20120315103923.GL2304@redhat.com> <4F61D1AF.4040603@siemens.com> <4F61D688.5040406@redhat.com>
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At 03/15/2012 07:46 PM, Avi Kivity Wrote:
> On 03/15/2012 01:25 PM, Jan Kiszka wrote:
>>>>
>>> There was such vm exit (KVM_EXIT_HYPERCALL), but it was deemed to be a
>>> bad idea.
>>
>> BTW, this would help a lot in emulating hypercalls of other hypervisors
>> (or of KVM's VAPIC in the absence of in-kernel irqchip - I had to jump
>> through hoops therefore) in user space. Not all those hypercall handlers
>> actually have to reside in the KVM module.
>>
> 
> That is true.  On the other hand the hypercall ABI might go to pieces if
> there was no central implementation.
> 

I prefer this:
host <-> guest kernel: use hypercall

host <-> guest userspace: use virtio-serial(or other way that not modify kernel)

Thanks
Wen Congyang