[pve-devel] [PATCH docs v2 18/18] qm: machine version: document support in PVE

[Fiona Ebner]

Elaborate on new QEMU machine version removal policy and how PVE will
support machine versions. Make sure to also mention the years, so that
users immediately have a good idea for how long it will be.

Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---

Changes in v2:
* get rid of outdated information from "Update to a Newer Machine
  Version" section
* drop sentence about early pre-deprecation warning (doesn't exist
  anymore)

 qm.adoc | 39 +++++++++++++++++++++++++++++++--------
 1 file changed, 31 insertions(+), 8 deletions(-)

diff --git a/qm.adoc b/qm.adoc
index 94fdd4e..9d8becf 100644
--- a/qm.adoc
+++ b/qm.adoc
@@ -173,19 +173,42 @@ This means that after a fresh start, the newest machine version supported by the
 QEMU binary is used (e.g. the newest machine version QEMU 8.1 supports is
 version 8.1 for each machine type).
 
+Starting with QEMU 10.1, machine versions will be removed from upstream QEMU
+after 6 years. In {pve}, major releases happen approximately every 2 years, so a
+major {pve} release will support machine versions from approximately two
+previous major {pve} releases, more details below.
+
+Before upgrading to a new major {pve} release, you should update VM
+configurations to avoid all machine versions that will be dropped during the
+next major {pve} release. This ensures that the guests can still be used
+throughout that release. See the section
+xref:qm_machine_update[Update to a Newer Machine Version].
+
+The following table shows the expected baselines of supported machine versions
+for the current and upcoming major {pve} releases (best guesses):
+
+[width="100%",cols=">s,>,>s,2*>",options="header"]
+|===============================================================================================
+| {pve} | active development | supported baseline | dropped during life cycle | last QEMU binary
+|     8 |          2023-2025 |                2.4 |             2.3 and older |              9.2
+|     9 |          2025-2027 |                6.0 |             5.2 and older |             11.2
+|    10 |          2027-2029 |                8.0 |             7.2 and older |             13.2
+|===============================================================================================
+
+NOTE: Support for {pve} releases is longer than active development, but no new
+QEMU binary versions will be added after active development, just backports and
+fixes for existing binary versions.
+
 [[qm_machine_update]]
 
 Update to a Newer Machine Version
 +++++++++++++++++++++++++++++++++
 
-Very old machine versions might become deprecated in QEMU. For example, this is
-the case for versions 1.4 to 1.7 for the i440fx machine type. It is expected
-that support for these machine versions will be dropped at some point. If you
-see a deprecation warning, you should change the machine version to a newer one.
-Be sure to have a working backup first and be prepared for changes to how the
-guest sees hardware. In some scenarios, re-installing certain drivers might be
-required. You should also check for snapshots with RAM that were taken with
-these machine versions (i.e. the `runningmachine` configuration entry).
+If you see a deprecation warning, you should change the machine version to a
+newer one. Be sure to have a working backup first and be prepared for changes to
+how the guest sees hardware. In some scenarios, re-installing certain drivers
+might be required. You should also check for snapshots with RAM that were taken
+with these machine versions (i.e. the `runningmachine` configuration entry).
 Unfortunately, there is no way to change the machine version of a snapshot, so
 you'd need to load the snapshot to salvage any data from it.
 
-- 
2.39.5