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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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=207.211.31.120; envelope-from=david@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/24 03:07:34 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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: virtio-dev@lists.oasis-open.org, Cornelia Huck , qemu-devel@nongnu.org, "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" >> GlobalProperty hw_compat_4_2[] =3D { >> { "virtio-blk-device", "queue-size", "128"}, >> { "virtio-scsi-device", "virtqueue_size", "128"}, >=20 > Okay, so the bit above is for after 5_0 is released then? Is there a Yes. > way to queue up a reminder or something so we get to it when the time > comes, or I just need to watch for 5.0 to come out and submit a patch > then? I think what happened usually happens is that someone introduces all the compat machines, sometimes directly with empty hw_compat. E.g., see commit 3eb74d2087d3bd6cb51c06a49ba94222248d2de4 Author: Cornelia Huck Date: Tue Nov 12 11:48:11 2019 +0100 hw: add compat machines for 5.0 Add 5.0 machine types for arm/i440fx/q35/s390x/spapr. and commit 9aec2e52ce9d9632a86be2d1d0dd493722d2e7be Author: Cornelia Huck Date: Wed Jul 24 12:35:24 2019 +0200 hw: add compat machines for 4.2 Add 4.2 machine types for arm/i440fx/q35/s390x/spapr. The latter already introduced hw_compat_4_1, for examnple. @Conny, do you already have a patch for 5.1 compat patch lying around somewhere? [...] > So I will probably go this route. It looks like that is the way we > went for free page reporting so it is easy enough to just do some > cut/paste/replace and have something ready to go later today without > having to second guess things. I remember that a v1->v2 vmstate migration works (e.g., old QEMU to new QEMU). But I can't tell from the top of my head what would happen when we migrate v2->v1 (e.g., new QEMU to old QEMU). My guess is that the latter won't work, but I might be wrong. Looking at migration/vmstate.c:vmstate_load_state() "incoming version_id ... is too new for local version_id" One would have to tell the new QEMU to send via vmstate v1 when running under the compat machine. I don't recall if and how that would be possible. So the other approach is a save bet. --=20 Thanks, David / dhildenb