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Tsirkin" Subject: Re: [PATCH] i386/acpi: restore device paths for pre-5.1 vms Message-ID: <20210326011250.74fb7a1e@redhat.com> In-Reply-To: <20210323152835-mutt-send-email-mst@kernel.org> References: <20210301195919.9333-1-cheptsov@ispras.ru> <20210322114116-mutt-send-email-mst@kernel.org> <20210323104542-mutt-send-email-mst@kernel.org> <71AD039B-775A-4DF3-B16D-4BC3768A20AC@ispras.ru> <20210323152835-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=imammedo@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=216.205.24.124; envelope-from=imammedo@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-stable@nongnu.org, Vitaly Cheptsov , Thomas Lamprecht , qemu devel list Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 23 Mar 2021 15:32:23 -0400 "Michael S. Tsirkin" wrote: > On Tue, Mar 23, 2021 at 04:04:11PM +0100, Thomas Lamprecht wrote: > > On 23.03.21 15:55, Vitaly Cheptsov wrote: =20 > > >> 23 =D0=BC=D0=B0=D1=80=D1=82=D0=B0 2021 =D0=B3., =D0=B2 17:48, Michae= l S. Tsirkin =D0=BD=D0=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB(= =D0=B0): > > >> > > >> The issue is with people who installed a VM using 5.1 qemu, > > >> migrated to 5.2, booted there and set a config on a device > > >> e.g. IP on a NIC. > > >> They now have a 5.1 machine type but changing uid back > > >> like we do will break these VMs. > > >> > > >> Unlikley to be common but let's at least create a way for these peop= le > > >> to used these VMs. > > >> =20 > > > They can simply set the 5.2 VM version in such a case. I do not want = to =20 > > let this legacy hack to be enabled in any modern QEMU VM version, as it= violates ACPI specification and makes the life more difficult for various = other software like bootloaders and operating systems. > >=20 > > Yeah here I agree with Vitaly, if they already used 5.2 and made some c= onfigurations > > for those "new" devices they can just keep using 5.2? =20 >=20 > People just create a VM, the machine type gets set in stone then. >=20 > > If some of the devices got configured on 5.1 and some on 5.2 there's no= thing we can > > do anyway, from a QEMU POV - there the user always need to choose one m= achine version > > and fix up the device configured while on the other machine. =20 >=20 > I think I did not explain it well. Here is an example. >=20 >=20 > 1. start qemu version 5.1 with machine type 5.1 >=20 > 2. reboot with qemu version 5.2 still machine type 5.1 >=20 > 3. set static IP on NIC >=20 > 4. reboot with qemu version 6.0 still machine type 5.1 >=20 > at this point NIC loses the static IP. >=20 >=20 >=20 > What I suggest is that we use a property to at stage 4, Question is how users would know about fixup property, nobody knows about i= t beside new QEMU. Or even better how to make it transparent to user, so the only action user would have to do is to upgrade to the newest QEMU. > user can set a flag and avoid losing the static IP. > Yes in theory maybe at stage 2 or 4 user can switch to 5.2 machine type > but we were always telling people not to do that, let's not start. >=20