From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:51565) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h0qiO-0001al-DA for qemu-devel@nongnu.org; Mon, 04 Mar 2019 11:45:21 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h0qiN-0000am-Ev for qemu-devel@nongnu.org; Mon, 04 Mar 2019 11:45:20 -0500 Date: Mon, 4 Mar 2019 17:45:01 +0100 From: Igor Mammedov Message-ID: <20190304174501.65381c02@redhat.com> In-Reply-To: <20190304150218.GN4239@redhat.com> References: <1551454936-205218-1-git-send-email-imammedo@redhat.com> <1551454936-205218-2-git-send-email-imammedo@redhat.com> <20190301154947.GJ21251@redhat.com> <20190301183328.20b63e23@redhat.com> <20190301174806.GN21251@redhat.com> <15464582-e8a6-6654-7679-15d87c10af38@redhat.com> <20190304145510.57c73177@redhat.com> <20190304135909.GL4239@redhat.com> <20190304155457.206a7ff7@redhat.com> <20190304150218.GN4239@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [Qemu-ppc] [libvirt] [PATCH 1/2] numa: deprecate 'mem' parameter of '-numa node' option List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. =?UTF-8?B?QmVycmFuZ8Op?=" Cc: Thomas Huth , peter.maydell@linaro.org, ehabkost@redhat.com, libvir-list@redhat.com, qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , qemu-arm@nongnu.org, qemu-ppc@nongnu.org, pbonzini@redhat.com, david@gibson.dropbear.id.au On Mon, 4 Mar 2019 15:02:18 +0000 Daniel P. Berrang=C3=A9 wrote: > On Mon, Mar 04, 2019 at 03:54:57PM +0100, Igor Mammedov wrote: > > On Mon, 4 Mar 2019 13:59:09 +0000 > > Daniel P. Berrang=C3=A9 wrote: > > =20 > > > On Mon, Mar 04, 2019 at 02:55:10PM +0100, Igor Mammedov wrote: =20 > > > > On Mon, 4 Mar 2019 09:11:19 +0100 > > > > Thomas Huth wrote: > > > > =20 > > > > > On 01/03/2019 18.48, Daniel P. Berrang=C3=A9 wrote: > > > > > [...] =20 > > > > > > So I think this patch has to be dropped & replaced with one that > > > > > > simply documents that memdev syntax is preferred. =20 > > > > >=20 > > > > > That's definitely not enough. I've had a couple of cases already = where > > > > > we documented that certain options should not be used anymore, and > > > > > people simply ignored it (aka. if it ain't broken, don't do any c= hange). > > > > > Then they just started to complain when I really tried to remove = the > > > > > option after the deprecation period. =20 > > > > =20 > > > > > So Igor, if you can not officially deprecate these things here ye= t, you > > > > > should at least make sure that they can not be used with new mach= ine > > > > > types anymore. Then, after a couple of years, when we feel sure t= hat > > > > > there are only some few or no people left who still use it with t= he old > > > > > machine types, we can start to discuss the deprecation process ag= ain, I > > > > > think. =20 > > > > Is it acceptable to silently disable CLI options (even if they are = broken > > > > like in this case) for new machine types? > > > > I was under impression that it should go through deprecation first.= =20 > > >=20 > > > Yes, it must go through deprecation. I was saying we can't disable > > > the CLI options at all, until there is a way for libvirt to correctly > > > use the new options. =20 > >=20 > > I'm not adding new options (nor plan to for numa case (yet)), > > -numa node,memdev is around several years by now and should be used > > as default for creating new configs. > >=20 > > In light of keeping 'mem' option around for old machines, > > Deprecation should have served for notifying users that legacy > > options will be disabled later on (for new machines at least > > if no way found for migration compatible transition for older ones). > >=20 > > What I'm mainly aiming here is to prevent using broken legacy options > > for new VMs (like in RHBZ1624223 case) and deprecation is the only way > > we have now to notify users about CLI breaking changes. =20 >=20 > The idea of doing advance warnings via deprecations is that applications > have time to adapt to the new mechanism several releases before the old > mechanism is removed/disabled. Since the new mechanism isn't fully > usable yet, applications can't adapt to use it. So we can't start the > deprecation process yet, as it would be telling apps to do a switch > that isn't possible for many to actually do. At least a hope attempt to deprecate 'mem', served its purpose somewhat. Now it's clear that libvirt defaults to wrong legacy mode and should use 'memdev' instead. I hope that it will be addressed on libvirt side regardless of the fate of 'mem' deprecation process. Basically new VM should default to 'memdev' if it's available.=20 > In the meantime, qemu-options.hx could be updated. It documents both > "mem" and "memdev" currently but doesn't tell people that "memdev" is > the preferred syntax for future usage / warn against using "mem". Will do so. >=20 > Regards, > Daniel