Re: [PATCH v4 05/19] kho: Add feature header for fine-grained ABI compatibility

[sashiko-bot@kernel.org]

> Serialized structures in KHO and Live Update Orchestrator currently rely
> on whole-structure compatibility strings or monolithic version fields to
> validate handed-over state across kexec. Any change to a serialized
> structure, even an optional additive field, requires bumping the
> compatibility string or version number and breaks live update between
> adjacent kernels.
> 
> Introduce a generic feature header (struct kho_ser_hdr) for serialized
> binary structures in include/linux/kho/abi/feature.h. Each subsystem
> groups the fields of its serialized structure under feature indices,
> starting with index 0 for base fields. When a subsystem adds a new
> capability, it appends new fields to the end of its payload structure
> under a new feature index. Retired fields are kept in place so existing
> field offsets never shift; if the type or format of a field needs to
> change, the existing field and feature are kept intact until retired and
> [ ... ]
> layout while deserialization helpers follow the incoming header.
> 
> Suggested-by: David Matlack <dmatlack@google.com>
> Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Signed-off-by: Tarun Sahu <tarunsahu@google.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261110050202.529473-1-tarunsahu@google.com?part=5