Re: [PATCH] docs/about: propose OS platform/arch support tiers

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Jan 15, 2026 at 09:39:13PM +0100, BALATON Zoltan wrote:
> On Thu, 15 Jan 2026, Daniel P. Berrangé wrote:
> > Informally we have approximately three groups of platforms
> > 
> > * Tier 1: fully built and fully tested by CI. Must always be
> >           kept working & regressions fixed immediately
> > 
> > * Tier 2: fully built and partially tested by CI. Should
> >           always be kept working & regressions fixed quickly
> > 
> > * Tier 3: code exists but is not built or tested by CI.
> >           Should not be intentionally broken but not
> > 	   guaranteed to work at any time. Downstream must
> > 	   manually test, report & fix bugs.
> > 
> > Anything else is "unclassified" and any historical code
> > remnants may be removed.
> > 
> > It is somewhat tricky to define unambiguous rules for each tier,
> > but this doc takes a stab at it. We don't need to cover every
> > eventuality. If we get the core points of view across, then it
> > at least sets the direction for maintainers/contributors/users.
> > Other aspects can be inferred with greater accuracy than today.
> > 
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> > 
> > This came out of the discussion about recent unnoticed breakage
> > in NetBSD builds and what maintainers are expected todo about
> > it (if anything)
> > 
> >  https://lists.nongnu.org/archive/html/qemu-devel/2026-01/msg02543.html
> > 
> > docs/about/build-platforms.rst | 152 +++++++++++++++++++++++++++++++++
> > 1 file changed, 152 insertions(+)
> > 
> > diff --git a/docs/about/build-platforms.rst b/docs/about/build-platforms.rst
> > index e95784cdb5..950e164c02 100644
> > --- a/docs/about/build-platforms.rst
> > +++ b/docs/about/build-platforms.rst


> > +Tier 3
> > +~~~~~~
> > +
> > +These platforms have theoretical support in the code, but have
> > +little, or no, automated build and test coverage. Downstream
> > +consumers (users or distributors) who care about these platforms
> > +are requested to perform manual testing, report bugs and provide
> > +patches.
> > +
> > + * Builds and tests may be broken at any time in Git HEAD and
> > +   releases
> > +
> > + * Builds are not integrated into CI
> > +
> > + * Tests are not integrated into CI
> > +
> > + * Merging code is not gated
> > +
> > +This covers:
> > +
> > + * NetBSD
> > + * OpenBSD
> > + * macOS (except aarch64)
> > + * FreeBSD (except x86_64)
> > + * Windows (except x86_64)
> > + * Solaris
> > +
> > +Responsibilities:
> > +
> > + * Contributors MAY test patches on Tier 3 platforms manually
> > +
> > + * Maintainers MAY request contributors to fix problems
> > +   on Tier 3 platforms
> > +
> > + * Maintainers MAY test patches on Tier 3 platforms manually
> > +
> > + * Maintainers SHOULD NOT accept patches that remove code
> > +   targetting Tier 3 platforms even if currently broken
> 
> If an OS stops supporting a platform in new versions then due to the policy
> of supporting only the last two OS versions in QEMU may lead to breaking
> this. Maybe it tries to say that Tier 3 is intended to be fixed but no
> guarantees on when? It is also clarified below so maybe this clause is not
> needed or need to be reworded?

The policy on only supporting the most recent 2 releases of an
OS applies universally regardless of the Tier levels. I should
state that explicitly in this new doc to make that clear.

IOW, maintainers are free to remove code that is only relevant
to OS versions /older/ than 2 releases whether that code is
broken or not.


> 
> > + * Downstream vendors SHOULD test RC releases on Tier 3 platforms
> > +   and provide bug reports and patches to address problems
> > +
> > +Note: if a Tier 3 platform is found to be significantly broken,
> > +no patches are contributed for a prolonged period, and there is
> > +no sign of downstream usage, it is liable to be moved to
> > +"Unclassified" and thus be subject to removal.
> > +
> > +
> > +Unclassified
> > +~~~~~~~~~~~~
> > +
> > +These platforms are not intended to be supported in the code
> > +and outside the scope of any support tiers.
> > +
> > +  * Code supporting these platforms can removed at any time
> 
> can be removed
> 
> > +  * Bugs reports related to these platforms will generally
> > +    be ignored
> > +
> > +This covers:
> > +
> > + * All 32-bit architectures on any OS
> > + * Any OS not listed above
> > +
> > +Responsibilities:
> > +
> > + * Maintainers MAY decline patches that add code targetting
> > +   unclassified platforms
> > +
> > + * Maintainers MAY accept patches that remove code targetting
> > +   unclassified platforms

With regards,
Daniel
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