Daniel P. Berrangé <[email protected]> writes: > On Wed, Dec 17, 2025 at 03:06:57PM +0100, Philippe Mathieu-Daudé wrote: >> We couldn't find a way (guest OS with VirtIO drivers) to test >> a legacy VirtIO device on a ARM vCPU running in big-endian. >> >> Deprecate for the v11.0 release, giving 1 year to users who >> really care to contribute functional tests. >> >> Suggested-by: Alex Bennée <[email protected]> >> Signed-off-by: Philippe Mathieu-Daudé <[email protected]> >> --- >> docs/about/deprecated.rst | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst >> index ac31a2bce42..3a69facb0f1 100644 >> --- a/docs/about/deprecated.rst >> +++ b/docs/about/deprecated.rst >> @@ -515,6 +515,17 @@ It was implemented as a no-op instruction in TCG up to >> QEMU 9.0, but >> only with ``-cpu max`` (which does not guarantee migration compatibility >> across versions). >> >> +VirtIO devices >> +'''''''''''''' >> + >> +Legacy VirtIO devices on Big-Endian ARM architecture (since 11.0) >> +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >> + >> +There are no functional tests for legacy virtio devices used by ARM >> +machines running in big-endian order, which makes harder to maintain >> +the code path while the code base evolve. > > Lack of test coverage is not a reason to deprecate something. > > We deprecate things we intend to intentionally remove or intentionally > change in an incompatible manner.
We also deprecate things that stop us moving the code forward. c.f. the long process to deprecate 32 bit hosts. > If something is not tested, that merely means it has lesser quality > guarantees, and is liable to unintenionally get broken at times. > > If we're planning to *intentionally* remove the ability to use > legacy virtio on big endian, that would be a reason to deprecate. > If so the deprecation message should say this, not talk about > missing functional testing. As far as I'm aware BE Arm is a very small niche and I'm not even sure anyone runs BE Arm systems with VirtIO - let alone legacy VirtIO. If there are people that need this functionality they need to at least make themselves known. -- Alex Bennée Virtualisation Tech Lead @ Linaro
