From mboxrd@z Thu Jan  1 00:00:00 1970
From: Anthony Liguori <aliguori@us.ibm.com>
Subject: Re: Balloon device in qemu?
Date: Sun, 03 Aug 2008 20:05:44 -0500
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Cc: Marcelo Tosatti <mtosatti@redhat.com>,
	Avi Kivity <avi@qumranet.com>, KVM list <kvm@vger.kernel.org>
To: Andrea Arcangeli <andrea@qumranet.com>
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Andrea Arcangeli wrote:
> On Fri, Aug 01, 2008 at 02:47:39PM -0500, Anthony Liguori wrote:
>   
>> Is there a way to detect MMU notifiers from userspace?  I don't think it's 
>> currently safe to madvise unconditionally.
>>     
>
> There is no way to detect mmu notifiers from userspace (well strictly
> speaking you could check /proc/kallsyms) but the point is that without
> mmu notifiers madvise won't be enough (the memory may not be freed
> without the other ioctl proposed by Marcelo that also flushes sptes).
>   

Right.  Ideally, I'd like to just disable the balloon device if mmu 
notifiers *and* kvm support for it are not present.  If you're saying 
there is no way to probe for this now from userspace, then that's 
something we need to add.

Regards,

Anthony Liguori