From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54992) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e1zzv-0003i4-PQ for qemu-devel@nongnu.org; Tue, 10 Oct 2017 15:15:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e1zzs-0007CN-Ik for qemu-devel@nongnu.org; Tue, 10 Oct 2017 15:15:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59318) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e1zzs-0007Bv-0k for qemu-devel@nongnu.org; Tue, 10 Oct 2017 15:15:20 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B7F064A702 for ; Tue, 10 Oct 2017 19:15:18 +0000 (UTC) Date: Tue, 10 Oct 2017 16:15:02 -0300 From: Eduardo Habkost Message-ID: <20171010191502.GA32108@localhost.localdomain> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20171010003951-mutt-send-email-mst@kernel.org> 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: "Michael S. Tsirkin" Cc: "Daniel P. Berrange" , qemu-devel@nongnu.org, anderson@redhat.com, =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Igor Mammedov , lersek@redhat.com 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: > > >=20 > > > > On Mon, Sep 11, 2017 at 06:59:24PM +0200, Marc-Andr=E9 Lureau wro= te: > > > > > See docs/specs/vmcoreinfo.txt for details. > > > > >=20 > > > > > "etc/vmcoreinfo" fw_cfg entry is added when using "-device vmco= reinfo". =20 > > > >=20 > > > > I'm wondering if you considered just adding the entry to fw_cfg b= y > > > > default, without requiring any -device arg ? Unless I'm misunders= tanding, > > > > this doesn't feel like a device to me - its just a well known buc= ket > > > > in fw_cfg IIUC ? Obviously its existance would need to be tied t= o > > > > the latest machine type for ABI reasons though. The benefit of th= is > > > > is that it would "just work" without us having to plumb it throug= h to > > > > all the downstream applications that use QEMU for mgmt guest (Ope= nStack, > > > > oVirt, GNOME Boxes, virt-manager, and countless other mgmt apps). > > > it follows model set by pvpanic device, it's easier to manage from = migration > > > POV, one could use it even for old machine types with new qemu (jus= t by adding > > > device, it makes instance not backwards migratable to old qemu but = should work > > > for forward migration) and if user doesn't need it, device could be= just omitted > > > from CLI. > >=20 > > Sure but it means that in effect no one will have this functionality = enabled > > for several years. pvpanic has been around a long time and I rarely s= ee it > > present in configured guests :-( > >=20 > >=20 > > Regards, > > Daniel >=20 > libvirt runs with -nodefaults, right? I'd argue pretty strongly -nodefa= ults > shouldn't add optional devices anyway. Does it mean every time we make a PC device configurable, we should make it be disabled by -nodefaults, and require libvirt to adapt? I don't think that would be a good idea. Imagine the hassle the "pc: make .* configurable" patches[1] would generate for libvirt. >=20 > So it's up to you guys, you can add it to VMs by default if you want to= . To be honest, I think "no defaults" is a misleading name for an option. If it really meant "create no optional device at all", it would eventually become a synonym for "-machine none", and I don't think that's its goal. I expect PC to always have a set of devices/features that are disabled by -nodefaults, and a set of devices/features that are not disabled by -nodefaults. We need good judgement to decide on which set the device will be, and I believe Daniel exposed good arguments to put vmcoreinfo in the second set. [1] https://www.mail-archive.com/qemu-devel@nongnu.org/msg393493.html Subject: [RFC PATCH v2 00/12] Guest startup time optimization --=20 Eduardo