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Fri, 04 Sep 2026 22:17:15 -0700 (PDT) Received: from ehlo.thunderbird.net ([195.174.135.130]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49cee80eda4sm200070045e9.15.2026.09.04.22.17.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Sep 2026 22:17:15 -0700 (PDT) Date: Sat, 05 Sep 2026 04:53:35 +0000 From: Gabriele Monaco To: Alexei Starovoitov , Steven Rostedt CC: Nam Cao , LKML , linux-trace-kernel , bpf , Wen Yang , Tobias Schaffner , Viktor Malik , Linus Torvalds Subject: Re: [RFC PATCH 00/20] rv: Add support for BPF monitors In-Reply-To: References: <20260831090524.106845-1-gmonaco@redhat.com> <87se3sakgi.fsf@yellow.woof> <20260903090211.50d15220@gandalf.local.home> <20260904074317.01b2c0e1@robin> <20260904123108.1fa1d815@gandalf.local.home> <20260904132421.111c0279@gandalf.local.home> <20260904194620.0c7a8363@gandalf.local.home> <20260904201741.2986efca@gandalf.local.home> Message-ID: <228FE969-EBFF-4B60-B0E7-C1E4FD82FB8B@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Il 5 settembre 2026 00:22:01 UTC, Alexei Starovoitov ha scritto: >On Fri, Sep 4, 2026 at 5:16=E2=80=AFPM Steven Rostedt wrote: >> >> On Fri, 4 Sep 2026 16:48:55 -0700 >> Alexei Starovoitov wrote: >> >> > On Fri, Sep 4, 2026 at 4:45=E2=80=AFPM Steven Rostedt wrote: >> > > >> > > On Fri, 04 Sep 2026 16:34:00 -0700 >> > > "Alexei Starovoitov" wrote: >> > > >> > > > bpf in 2022 was surely less capable then it is today=2E >> > > > It took us 2 years of bpf core development to statisfy sched-ext = demands >> > > > and we're still adding new features for sched-ext needs=2E >> > > > If you're trully willing to remove 90% of kernel/trace/rv/ and re= factor >> > > > it into tiny shim where all of the core pieces are bpf driven we = can >> > > > certainly work together (like we did with sched-ext) and add what= ever >> > > > is missing on bpf side=2E Then all existing monitors will become = bpf programs=2E >> > > > But adding bpf as another 'monitor', sorry but hard NO=2E >> > > > If hardcoded monitors was a mistake then admit it and fix it by d= eleting it, >> > > > if it's not a mistake then keep adding hardcoded monitors=2E Alexei, what I read from your opinion is: if you really want to do this RV= thing, then you should just implement it all in BPF=2E Please correct me if I'm wrong, but I don't see how this series isn't a st= ep towards it=2E I am obviously open to all sorts of criticism on /how/ I'm= doing it=2E We are adding the possibility to write (existing or new) monitors in BPF, = not adding another fat "bpf monitor"=2E And if you believe my attempt to have in-kernel and BPF monitors coexist i= s a waste of time, I get that too and I'm open to discuss=2E As you mentioned, when the project started, BPF was just not ready=2E My i= ntention with this series is to reassess this today=2E RV was initially built with the functional safety use-case in mind=2E For = various technical reasons this didn't take off, but that scenario drove tow= ards implementing RV reactors like the panic() one=2E Something BPF just sh= ouldn't do, as I get it=2E The interoperability with other tools (via RV-generated tracepoints) was a= lso a driving factor, together with Daniel probably being more proficient w= ith those back then=2E That's just from the top of my head: there are historical and technical re= asons for why RV looks like it is today, whether those are valid or just "m= istakes" is simply not for us to say=2E I'd rather discuss on what is the best approach /today/=2E And that's prec= isely why I submitted the talk for LPC=2E Gabriele