From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:49954) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T62oX-0006WB-Bb for qemu-devel@nongnu.org; Mon, 27 Aug 2012 13:09:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1T62oU-0004gC-TO for qemu-devel@nongnu.org; Mon, 27 Aug 2012 13:09:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:15270) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T62oU-0004ft-Km for qemu-devel@nongnu.org; Mon, 27 Aug 2012 13:09:22 -0400 Message-ID: <503BA9BC.5010207@redhat.com> Date: Mon, 27 Aug 2012 10:09:16 -0700 From: Avi Kivity MIME-Version: 1.0 References: <1345801763-24227-1-git-send-email-qemulist@gmail.com> <1345801763-24227-11-git-send-email-qemulist@gmail.com> <503792F1.4090109@redhat.com> <503B1B4B.6050108@redhat.com> <503B260E.70607@web.de> In-Reply-To: <503B260E.70607@web.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 10/10] qdev: fix create in place obj's life cycle problem List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Paolo Bonzini , Liu Ping Fan , liu ping fan , Anthony Liguori , qemu-devel@nongnu.org On 08/27/2012 12:47 AM, Jan Kiszka wrote: > On 2012-08-27 09:01, Paolo Bonzini wrote: > > Il 25/08/2012 09:42, liu ping fan ha scritto: > >>>> > >>>> I don't see why MMIO dispatch should hold the IDEBus ref rather than the > >>>> PCIIDEState. > >>>> > >> When transfer memory_region_init_io() 3rd para from void* opaque to > >> Object* obj, the obj : opaque is not neccessary 1:1 map. For such > >> situation, in order to let MemoryRegionOps tell between them, we > >> should pass PCIIDEState->bus[0], bus[1] separately. > > > > The rule should be that the obj is the object that you want referenced, > > and that should be the PCIIDEState. > > > > But this is anyway moot because it only applies to objects that are > > converted to use unlocked dispatch. This likely will not be the case > > for IDE. > > BTW, I'm pretty sure - after implementing the basics for BQL-free PIO > dispatching - that device objects are the wrong target for reference > counting. We keep memory regions in our dispatching tables (PIO > dispatching needs some refactoring for this), and those regions need > protection for BQL-free use. Devices can't pass away as long as the have > referenced regions, memory region deregistration services will have to > take care of this. > > I'm currently not using reference counting at all, I'm enforcing that > only BQL-protected regions can be deregistered. That's a pretty harsh constraint. > Also note that there seems to be another misconception in the > discussions: deregistration is not only bound to device unplug. It also > happens on device reconfiguration, e.g. PCI BAR (re-)mapping. Another > strong indicator that we should worry about individual memory regions, > not devices. > > Deregistration is fine, the problem is destruction. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.