Re: [PATCH] docs/about: Automatically deprecate versioned machine types older than 6 years

On Tue, Apr 30, 2024 at 08:45:29AM +0200, Thomas Huth wrote: > Old machine types often have bugs or work-arounds that affect our > possibilities to move forward with the QEMU code base (see for example > https://gitlab.com/qemu-project/qemu/-/issues/2213 for a bug that likely > cannot be fixed without breaking live migration with old machine types, > or https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg04516.html or > commit ea985d235b86). So instead of going through the process of manually > deprecating old machine types again and again, let's rather add an entry > that can stay, which declares that machine types older than 6 years are > considered as deprecated automatically. Six years should be sufficient to > support the release cycles of most Linux distributions. Reading this again, I think we're mixing two concepts here. With this 6 year cut off, we're declaring the actual *removal* date, not the deprecation date. A deprecation is something that happens prior to removal normally, to give people a warning of /future/ removal, as a suggestion that they stop using it. If we never set the 'deprecation_reason' on a machine type, then unless someone reads this doc, they'll never realize they are on a deprecated machine. When it comes to machine types, I see deprecation as a way to tell people they should not deploy a /new/ VM on a machine type, only use it for back compat (incoming migration / restore from saved image) with existing deployed VMs. If we delete a machine on the 6 year anniversary, then users don't want to be deploying /new/ VMs using that on the 5 year anniversary as it only gives a 1 year upgrade window. So how long far back do we consider it reasonable for a user to deploy a /new/ VM on an old machine type ? 1 year, 2 years, 3 years ? How about picking the half way point ? 3 years ? ie, set deprecation_reason for any machine that is 3 years old, but declare that our deprecation cycle lasts for 3 years, instead of the normal 1 year, when applied to machine types. This would give a strong hint that users should get off the old machine type, several years before its finally deleted.