Documentation/bpf: Add a description of "stable kfuncs" #4345
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Following up on the discussion at the BPF office hours, this patch adds a description of the (new) concept of "stable kfuncs", which are kfuncs that offer a "more stable" interface than what we have now, but is still not part of UAPI. This is mostly meant as a straw man proposal to focus discussions around stability guarantees. From the discussion, it seemed clear that there were at least some people (myself included) who felt that there needs to be some way to export functionality that we consider "stable" (in the sense of "applications can rely on its continuing existence"). One option is to keep BPF helpers as the stable interface and implement some technical solution for moving functionality from kfuncs to helpers once it has stood the test of time and we're comfortable committing to it as a stable API. Another is to freeze the helper definitions, and instead use kfuncs for this purpose as well, by marking a subset of them as "stable" in some way. Or we can do both and have multiple levels of "stable", I suppose. This patch is an attempt to describe what the "stable kfuncs" idea might look like, as well as to formulate some criteria for what we mean by "stable", and describe an explicit deprecation procedure. Feel free to critique any part of this (including rejecting the notion entirely). Some people mentioned (in the office hours) that should we decide to go in this direction, there's some work that needs to be done in libbpf (and probably the kernel too?) to bring the kfunc developer experience up to par with helpers. Things like exporting kfunc definitions to vmlinux.h (to make them discoverable), and having CO-RE support for using them, etc. I kinda consider that orthogonal to what's described here, but I added a placeholder reference indicating that this (TBD) functionality exists. Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
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Upstream branch: dfff86f |
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At least one diff in series https://patchwork.kernel.org/project/netdevbpf/list/?series=712540 expired. Closing PR. |
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Pull request for series with
subject: Documentation/bpf: Add a description of "stable kfuncs"
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=712540