From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57314) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ws6Fj-0006Vp-Lx for qemu-devel@nongnu.org; Wed, 04 Jun 2014 04:09:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ws6Fa-0005Zr-L5 for qemu-devel@nongnu.org; Wed, 04 Jun 2014 04:08:55 -0400 Received: from mail-we0-x230.google.com ([2a00:1450:400c:c03::230]:58282) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ws6Fa-0005YX-Cj for qemu-devel@nongnu.org; Wed, 04 Jun 2014 04:08:46 -0400 Received: by mail-we0-f176.google.com with SMTP id q59so7822130wes.7 for ; Wed, 04 Jun 2014 01:08:45 -0700 (PDT) Date: Wed, 4 Jun 2014 10:08:41 +0200 From: Stefan Hajnoczi Message-ID: <20140604080841.GC21259@stefanha-thinkpad.redhat.com> References: <1401448669-4655-1-git-send-email-stefanha@redhat.com> <20140603171123.49fb8b8f.cornelia.huck@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140603171123.49fb8b8f.cornelia.huck@de.ibm.com> Subject: Re: [Qemu-devel] [PATCH v3 0/8] virtio-blk: use alias properties in transport devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cornelia Huck Cc: peter.crosthwaite@xilinx.com, qemu-devel@nongnu.org, Stefan Hajnoczi , pbonzini@redhat.com, afaerber@suse.de, fred.konrad@greensocs.com On Tue, Jun 03, 2014 at 05:11:23PM +0200, Cornelia Huck wrote: > On Fri, 30 May 2014 13:17:41 +0200 > Stefan Hajnoczi wrote: > > > v3: > > * Split qdev_alias_all_properties() into its own patch [Peter Crosthwaite] > > * Do not dereference DEVICE_CLASS(class) inline [Peter Crosthwaite] > > > > v2: > > * Add qdev_alias_all_properties() instead of virtio-blk-specific function [Paolo] > > * Explain refcount handling in doc comment [Paolo] > > * Fix "property" duplicate typo [Peter Crosthwaite] > > * Add "the same object or" to clarify commit description [Igor] > > > > Thanks for the feedback on the RFC. This time around the alias property is > > implemented at the QOM property level instead of at the qdev property level. > > > > Note that this series only addresses virtio-blk. In later series we can > > convert virtio net, scsi, rng, and serial. > > > > The virtio transport/device split is broken as follows: > > > > 1. The virtio-blk device is never finalized because the transport devices > > (virtio-blk-pci and friends) leak the refcount. > > > > 2. If we fix the refcount leak then we double-free the 'serial' string property > > upon hot unplug since its char* is copied into the virtio-blk device which > > has an identical 'serial' qdev property. > > > > This series solves both of these problems as follows: > > > > 1. Introduce a QOM alias property that lets the transport device forward > > property accesses into the virtio device (the child). > > > > 2. Use alias properties in transport devices, instead of keeping a duplicate > > copy of the VirtIOBlkConf struct. > > > > 3. Fix the virtio-blk device refcount leak. It's now safe to do this since the > > double-free has been resolved. > > > > Tested that hotplug/hotunplug of virtio-blk-pci still works. > > FWIW: > > I gave your qom-alias-property branch a quick test on s390. > > virtio-ccw: seems to work fine, hotunplug of virtio-blk-ccw is still > fine, and the virtio-blk memory leaks due to missing finalization that > valgind complained about are gone. > > s390-virtio: still boots, but with x-data-plane=on we get the > predictable segfault in virtio_blk_data_plane_start() since s390-virtio > doesn't do notifiers. Maybe the dataplane code should do a quick check > for existence of the notifier callback when it allocates the dataplane > structure? Okay, good idea. Thanks! Stefan