From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35792) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e1w7I-0001QA-6O for qemu-devel@nongnu.org; Tue, 10 Oct 2017 11:06:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e1w7B-0008Fd-P0 for qemu-devel@nongnu.org; Tue, 10 Oct 2017 11:06:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43496) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e1w7B-0008FM-FO for qemu-devel@nongnu.org; Tue, 10 Oct 2017 11:06:37 -0400 Date: Tue, 10 Oct 2017 16:06:28 +0100 From: "Daniel P. Berrange" Message-ID: <20171010150628.GI30015@redhat.com> Reply-To: "Daniel P. Berrange" References: <20170911165929.2791-1-marcandre.lureau@redhat.com> <20170911165929.2791-3-marcandre.lureau@redhat.com> <20171009110336.GA17824@redhat.com> <20171009144344.38bbd1e9@nial.brq.redhat.com> <20171009130218.GK2954@redhat.com> <20171010003951-mutt-send-email-mst@kernel.org> <20171010083143.GA30015@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v6 2/7] hw/misc: add vmcoreinfo device List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?utf-8?Q?Marc-Andr=C3=A9?= Lureau Cc: "Michael S. Tsirkin" , Eduardo Habkost , QEMU , Dave Anderson , Igor Mammedov , Laszlo Ersek On Tue, Oct 10, 2017 at 05:00:18PM +0200, Marc-Andr=C3=A9 Lureau wrote: > Hi >=20 > On Tue, Oct 10, 2017 at 10:31 AM, Daniel P. Berrange > wrote: > > On Tue, Oct 10, 2017 at 12:44:26AM +0300, Michael S. Tsirkin wrote: > >> On Mon, Oct 09, 2017 at 02:02:18PM +0100, Daniel P. Berrange wrote: > >> > On Mon, Oct 09, 2017 at 02:43:44PM +0200, Igor Mammedov wrote: > >> > > On Mon, 9 Oct 2017 12:03:36 +0100 > >> > > "Daniel P. Berrange" wrote: > >> > > > >> > > > On Mon, Sep 11, 2017 at 06:59:24PM +0200, Marc-Andr=C3=A9 Lure= au wrote: > >> > > > > See docs/specs/vmcoreinfo.txt for details. > >> > > > > > >> > > > > "etc/vmcoreinfo" fw_cfg entry is added when using "-device v= mcoreinfo". > >> > > > > >> > > > I'm wondering if you considered just adding the entry to fw_cf= g by > >> > > > default, without requiring any -device arg ? Unless I'm misund= erstanding, > >> > > > this doesn't feel like a device to me - its just a well known = bucket > >> > > > in fw_cfg IIUC ? Obviously its existance would need to be tie= d to > >> > > > the latest machine type for ABI reasons though. The benefit of= this > >> > > > is that it would "just work" without us having to plumb it thr= ough to > >> > > > all the downstream applications that use QEMU for mgmt guest (= OpenStack, > >> > > > oVirt, GNOME Boxes, virt-manager, and countless other mgmt app= s). > >> > > it follows model set by pvpanic device, it's easier to manage fr= om migration > >> > > POV, one could use it even for old machine types with new qemu (= just by adding > >> > > device, it makes instance not backwards migratable to old qemu b= ut should work > >> > > for forward migration) and if user doesn't need it, device could= be just omitted > >> > > from CLI. > >> > > >> > Sure but it means that in effect no one will have this functionali= ty enabled > >> > for several years. pvpanic has been around a long time and I rarel= y see it > >> > present in configured guests :-( > >> > > >> > > >> > Regards, > >> > Daniel > >> > >> libvirt runs with -nodefaults, right? I'd argue pretty strongly -nod= efaults > >> shouldn't add optional devices anyway. > > > > This isn't really adding a device though is it - it is just a well kn= own > > location in fw_cfg to receive data. >=20 > Enabling the device on some configurations by default can be done as a > follow-up patch. Can we get this series reviewed & merged? The problem with the -device approach + turning it on by default is that = there is no way to turn it off again if you don't want it. eg there's way to un= do an implicit '-device foo' except via -nodefaults, but since libvirt uses = that already it would negate the effect of enabling it by default unconditiona= lly. Your previous approach of "-global fw_cfg.vmcoreinfo=3Don" is nicer in th= is respect, as you can trivially turn it on/off, overriding the default stat= e in both directions. Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| |: https://libvirt.org -o- https://fstop138.berrange.c= om :| |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|