From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59780) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZOgTT-0005YG-V0 for qemu-devel@nongnu.org; Mon, 10 Aug 2015 02:22:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZOgTM-0006MF-0r for qemu-devel@nongnu.org; Mon, 10 Aug 2015 02:22:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49533) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZOgTL-0006M8-S8 for qemu-devel@nongnu.org; Mon, 10 Aug 2015 02:22:11 -0400 Message-ID: <55C8430F.90505@redhat.com> Date: Mon, 10 Aug 2015 14:22:07 +0800 From: Jason Wang MIME-Version: 1.0 References: <20150807012346-mutt-send-email-mst@redhat.com> <55C43D17.6010902@redhat.com> <20150807124942.6c127a6b.cornelia.huck@de.ibm.com> In-Reply-To: <20150807124942.6c127a6b.cornelia.huck@de.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] virtio 1 issues List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cornelia Huck Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" On 08/07/2015 06:49 PM, Cornelia Huck wrote: > On Fri, 07 Aug 2015 13:07:35 +0800 > Jason Wang wrote: > >>> 2. ring resizing is broken - it actually has a comment: >>> /* TODO: need a way to put num back on reset. */ >>> guest that runs out of memory might down-size the ring. >>> Afterwards, ring size won't come back up after reset - not nice. >>> >> Then we need a new field to keep track the original queue size and >> migrate this. > virtio-ccw neatly sidesteps it by not implementing ring size changes at > all :) > > But it isn't really all good, see > > /* TODO: Add interface to handle vring.num changing */ > > We either need to implement this or fence off changing the ring size, I > guess. Yes. >>> Given that the modern layout is disabled by default, >>> I don't think these are release blockers. >>> >> Yes and looks like we need a new subsection and transport specific >> callbacks to fix above? > Agreed, it's not urgent as virtio-1 is not yet the default (and not > even enabled for ccw). > > I'm not sure we need transport-specific callbacks. Shouldn't the core > be able to track initial and actual size (and migrate in an optional > subsection), as long as the transports use defined interfaces to > interact with it? > For size, I agree it should be tracked by core. But we need also track transport specific data like dfselect/gfselect for pci.