From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:50442)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <aik@ozlabs.ru>) id 1axWJc-0003Ec-1o
	for qemu-devel@nongnu.org; Tue, 03 May 2016 05:08:30 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <aik@ozlabs.ru>) id 1axWJH-0006SK-7G
	for qemu-devel@nongnu.org; Tue, 03 May 2016 05:08:18 -0400
Received: from mail-pf0-x232.google.com ([2607:f8b0:400e:c00::232]:36481)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <aik@ozlabs.ru>) id 1axWJF-0006E5-Ud
	for qemu-devel@nongnu.org; Tue, 03 May 2016 05:08:03 -0400
Received: by mail-pf0-x232.google.com with SMTP id c189so7732889pfb.3
	for <qemu-devel@nongnu.org>; Tue, 03 May 2016 02:07:47 -0700 (PDT)
From: Alexey Kardashevskiy <aik@ozlabs.ru>
Message-ID: <65fbea72-f65f-fda9-775c-f9044f1e144d@ozlabs.ru>
Date: Tue, 3 May 2016 19:07:39 +1000
MIME-Version: 1.0
Content-Type: text/plain; charset=koi8-r; format=flowed
Content-Transfer-Encoding: 7bit
Subject: [Qemu-devel] memory_listener_unregister does not call region_del()
 - why?
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel/>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: David Gibson <david@gibson.dropbear.id.au>, Paolo Bonzini <pbonzini@redhat.com>, Alex Williamson <alex.williamson@redhat.com>

Hi!

Noticed a thing - when we do vfio-pci hotplug, we register a memory 
listener on PCI address space:

memory_listener_register(&container->listener, container->space->as);

Then on the "pseries" machine, I add IOMMU subregions and this ends up in 
vfio_listener_region_add() where I can create hardware window and hook it 
to KVM, etc, some stuff. So far so good.

Now I am trying hot unplug. So vfio_instance_finalize() is called, and from 
it - vfio_put_group -> vfio_disconnect_container -> vfio_listener_release 
-> memory_listener_unregister(&container->listener), as expected.

Hoewever, unlike memory_listener_register() (which calls region_add() 
callbacks), memory_listener_unregister() is as simple as this:

void memory_listener_unregister(MemoryListener *listener)
{
     QTAILQ_REMOVE(&memory_listeners, listener, link);
}

No region_del() calls => no proper cleanup. Hm.

Is there any particular reason for it to be that simple and there is 
another way to be notified about some memory listener being unregistered? 
Thanks.


-- 
Alexey