From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: kvm: qemu: stop/start cpus before/after devices
Date: Thu, 26 Mar 2009 13:36:40 -0300
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Cc: kvm-devel <kvm@vger.kernel.org>, Dor Laor <dlaor@redhat.com>,
	Yaniv Kamay <yaniv@redhat.com>
To: Avi Kivity <avi@redhat.com>
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On Thu, Mar 26, 2009 at 12:03:30PM +0200, Avi Kivity wrote:
> Marcelo Tosatti wrote:
>> On Wed, Mar 25, 2009 at 11:26:19AM -0300, Marcelo Tosatti wrote:
>>   
>>> On Wed, Mar 25, 2009 at 01:45:52PM +0200, Avi Kivity wrote:
>>>     
>>>> Marcelo Tosatti wrote:
>>>>       
>>>>> From: Yaniv Kamay <yaniv@qumranet.com>
>>>>>
>>>>> Stop cpus before devices when stopping the VM, start cpus after devices
>>>>> when starting VM.
>>>>>
>>>>>           
>>>> Why is this needed?
>>>>       
>>> A vcpu could access a stopped device otherwise.     
>>
>> Actually on vm_stop its safe because the order happens to be correct,
>> but on vm_start its the other way around (vcpus start first, and they
>> should be started last).
>>   
>
> But, we are holding qemu_mutex.  How can vcpus access the devices?

You're right, they can't. But its not bad to make it explicit, instead
of relying on the locking behaviour?