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Date: Thu, 26 Aug 2010 08:22:31 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH V2] balloon: Don't try fetching info if
	machine is stopped
References: <8450ea8e785c9049f0b3edddc01650a8c4b9ffe7.1282265244.git.amit.shah@redhat.com>	<4C719C7E.6030606@codemonkey.ws>	<20100826060513.GF18351@amit-laptop.redhat.com>	<4C762058.8070301@redhat.com>
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To: "Daniel P. Berrange" <berrange@redhat.com>
Cc: Amit Shah <amit.shah@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, agl@us.ibm.com, qemu list <qemu-devel@nongnu.org>, Juan Quintela <quintela@redhat.com>

On 08/26/2010 03:14 AM, Daniel P. Berrange wrote:
> On Thu, Aug 26, 2010 at 10:05:44AM +0200, Paolo Bonzini wrote:
>    
>> On 08/26/2010 08:05 AM, Amit Shah wrote:
>>      
>>> This is what I have currently. It would need some timer handling in
>>> the save/load case as well, right?
>>>        
>> When loading you won't have any pending "info balloon" command, so I
>> think the timer need not be preserved across migration.
>>
>> Also, 5 seconds for a stopped guest is actually a lot, so maybe Amit's
>> original patch or a variant thereof would make sense anyway.
>>      
> We should have a combination of both. If we know the guest is stopped
> we should return immediately, otherwise we should use the timer as a
> way to cope with a crashed/evil guest.
>    

Stopped doesn't necessarily mean that it's permanently stopped or even 
that a user has stopped it.

We stop a guest during live migration and in some other cases (like on 
disk error).

Returning immediately is an optimization on something that should be a 
proper fix.  Otherwise, you have a guest initiated DoS attack on 
management tools.

Regards,

Anthony Liguori

> Daniel
>