Re: [RFC PATCH 0/3] liveupdate: Move to feature flags for LUO and memfd ABI compatibility

On Thu, Sep 10, 2026 at 03:42:36PM -0700, Sean Christopherson wrote:

On Thu, Sep 10, 2026, Jason Gunthorpe wrote:

quoted

Sean's initial email was asking for strict never-break ABI compatability
rules on top, and that is what I've been reacting to.

No, I was never asking for that.  I think we just have a different interpretation
of ABI, or rather are talking about different pieces of ABI.

I am still asking for never-break serialization format compatibility, i.e. the
more literal save/restore ABI.  I'm not asking for full backwards/forwards
compatibility across all kernels version, i.e. the higher level "kernel" ABI.

To phrase things differently: I am a-ok if kernels are inherently incompatible
because they fundamentally operate differently and/or support different features.
I am not ok if we end up with incompatible kernels because the save/restore
interfaces and payloads are poorly designed, lack abstraction, etc.  

I can more agree with this, it is mostly what I thought we'd end up
doing anyhow with version numbers and growing the structs not
replacing them.

So you still end up with a version label (string I guess?) because we
can break it from time to time, just the version should have the
feature mechanism layered under it? I'm fine with that

Jason