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charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2026-09-02 at 18:57 -0700, Alexei Starovoitov wrote: > I don't think bpf fits here. I haven't seen active use of RV and even les= s > so of any request from people who want this kind of programmability. >=20 > So Nack for now. Sorry. Thanks for your opinion, however it sounds a bit harsh to me. RV is clearly not a popular tool, but I wouldn't say it doesn't have active= use: we're actively using it to validate the deadline scheduler/server changes a= nd it already found a number of issues (e.g. [1], [2]). The RTapp monitors are used to validate if userspace real-time applications interact with the kernel in the best way for predictability, as far as I'm = aware that's regularly used [3]. In my eyes, the missing piece of RV is in fact this programmability. Adding= a monitor now requires to write in-tree built-in kernel code. There are strong use cases for domain-specific rules that aren't general en= ough to belong in the kernel tree: * stricter RTapp rules that may not apply to all use-cases * verify some exotic system within Linux (e.g. a co-kernel [4]) * modelling for functional safety certification process (used for in-vehicl= e OSes like RHIVOS) BPF seems the natural tool for the job to me. Mind that RV monitors would b= e simple users of BPF, requiring only modifications in the RV subsystem but u= sing standard BPF facilities. I'm totally open to discuss on this though. Thanks, Gabriele [1] - https://lore.kernel.org/lkml/20260522125833.264145-1-gmonaco@redhat.c= om [2] - https://lore.kernel.org/lkml/20260113085159.114226-3-gmonaco@redhat.c= om [3] - https://lore.kernel.org/linux-rt-users/20260826132153.2476006-1-bigeasy@lin= utronix.de/T/#t [4] - https://lore.kernel.org/lkml/20260827072400.45734-1-tobias.schaffner@siemen= s.com