"Daniel P. Berrange" <berra...@redhat.com> writes: > There is currently no explicit guidance on the duration of support > for features such as versioned machine types, which have a finite > useful lifespan. Thus apps / users cannot predict how much time > they might be able to use a feature for, before it is removed (if > ever). > > This adds a new appendix that lists items which have finite lifecycles, > such as machine types. For items which are generally expected to be > supported indefinitely, it sets out the policy around deprecation > and removal, should it be needed. > > Signed-off-by: Daniel P. Berrange <berra...@redhat.com> > --- > qemu-doc.texi | 34 ++++++++++++++++++++++++++++++++++ > 1 file changed, 34 insertions(+) > > diff --git a/qemu-doc.texi b/qemu-doc.texi > index 29f89d8..e3c6400 100644 > --- a/qemu-doc.texi > +++ b/qemu-doc.texi > @@ -37,6 +37,7 @@ > * QEMU Guest Agent:: > * QEMU User space emulator:: > * Implementation notes:: > +* Support lifetime:: > * Deprecations:: > * License:: > * Index:: > @@ -3017,6 +3018,39 @@ Run the emulation in single step mode. > > @include qemu-tech.texi > > +@node Support lifetime > +@appendix Support lifetime > + > +Features provided by QEMU are subject to varying support lifetimes. > + > +In general features are intended to be supported indefinitely once > +introduced. In the event that a feature needs to be removed, there > +will be some period in which it will be marked as deprecated before > +eventual removal. All deprecated features will be listed in the > +``Deprecations'' appendix of this document. They may also generate > +warnings on the console when QEMU starts up, or if activated via > +a monitor command. > + > +Certain features will have an inherently finite lifetime, and thus > +will be removed on a fixed schedule. > + > +@node Machine types > +@section Machine types > + > +For architectures which aim to support live migration compatibility > +across releases, each release will introduce a new versioned machine > +type. For example, the 2.8.0 release introduced machine types > +``pc-i440fx-2.8'' and ``pc-q35-2.8' 'for the x86_64/i686 architectures. > + > +To allow live migration of a guest running on a 2.8.0 release to a > +2.9.0, the QEMU 2.9.0 version must support the ``pc-i440fx-2.8'' and > +``pc-q35-2.8''. To allow users live migrating VMs to skip multiple
"the ``pc-i440fx-2.8'' and ``pc-q35-2.8'' machine types". > +intermediate releases when upgrading, new releases of QEMU will > +support machine types from many previous versions. Suggest s/many/several/ > + > +The supported lifetime for machine types is 12 releases, which is > +equivalent to 4 years worth of previous QEMU releases. > + Do we have consensus on this? Peter? > @node Deprecations > @appendix Deprecations