From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D0E3D48095A; Thu, 3 Sep 2026 13:01:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788440484; cv=none; b=fPxs44Rwk45FAlypFuWef4g2bIz3wp2e2lfvPW2thMtr+0KOaNNsC4vC5rYoIqmSYMiSuIiuDWZCEYykN+NyPRPom1pHLhB5C9DkfFmo5klWlINJbCboIcXuc1a16ciSMxE3XutCTdmUluPK6DU8ud0ydQ71ujSwfp7fHjB4MM8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788440484; c=relaxed/simple; bh=iJG/s8GGXXXIrvxySAUuH638FurAcqctVoxjhxpgL6U=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=I8H+xiIrKVIivnOIYLF6mFXhgy9dMmQjPD6mQyNPfcL+ijvExqafuSFrj2LYp6TOxzGNvSeG6I8GqP8kkJtSGmNX9mqlYOoBjq1QPAvgkmhU0H4JstEA3cGcm9acfrb0Dr98+boFdw5DE6bD83eQUPVD7S6+Lsok/xBRUtPQPZo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; dkim=pass (1024-bit key) header.d=goodmis.org header.i=@goodmis.org header.b=JRUgXQ3A; arc=none smtp.client-ip=216.40.44.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=goodmis.org header.i=@goodmis.org header.b="JRUgXQ3A" Received: from omf13.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id A86ED120426; Thu, 3 Sep 2026 13:01:10 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf13.hostedemail.com (Postfix) with ESMTPA id 5DE8520012; Thu, 3 Sep 2026 13:01:08 +0000 (UTC) Date: Thu, 3 Sep 2026 09:02:11 -0400 From: Steven Rostedt To: Gabriele Monaco Cc: Alexei Starovoitov , Nam Cao , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, Wen Yang , Tobias Schaffner , Viktor Malik , Linus Torvalds Subject: Re: [RFC PATCH 00/20] rv: Add support for BPF monitors Message-ID: <20260903090211.50d15220@gandalf.local.home> In-Reply-To: References: <20260831090524.106845-1-gmonaco@redhat.com> <87se3sakgi.fsf@yellow.woof> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5DE8520012 X-Stat-Signature: 599b17rkjqqaboag1r5zzpsja34bpukq X-Rspamd-Server: rspamout07 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1/hDX2tycQ0wJ6OosjSOGEEIkQow8xfsuI= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=goodmis.org; h=date:from:to:cc:subject:message-id:in-reply-to:references:mime-version:content-type:content-transfer-encoding; s=dkim1; bh=YP1HmGaRtV48egavEcaNf/B8MIIrFxZMcAR9YqngWsc=; b=JRUgXQ3AifLYbcyEiPMjDDTlFTLfMtJCxMk4zNefD7BicPd3HHyGe1GyizkVC1OgKog0KY5+EYJIhR+cQKoDATPyZgRA5johHnmvhYqJ/B3EBeXRgsG2UcOpU9HkDEyktJrf5fnqgyBji4zBLVIjjkdepnqTRRI7+ReEbdkzqUI= X-HE-Tag: 1788440468-820146 X-HE-Meta: U2FsdGVkX1+/o5eHUAvWbIq34ly2XCcD6ZRuOhKJtTqfR40wgY1VcasY9LguqEVcrXg3FitwBLUK6RK5grbvCyqQ/+rZ/B356aenQJBarJmzBpukWDMHQYXLqhqiVQEdZQsT8BN+vVy/prEzh1Q/KPpuwLf/yHKmbsWNRbzLocF+euoO4KeU1/qUOmxX1DxuPOiNgB67ktypHkWAq0eG6f1TlyA3gM0YS++ewWGVm7i/VCS+coEwrw+IcYtQR8rkAA2SDKLZt6NthK+guE4kMsxezH9XtoaQrzeR80oHGXuXiO+MTgRNpPR5SH8w2VTZAGEiFLVl6wWZJ3+owXbfb/5UDIzE6YeROitbBSothSp69KXtAhrKKJIE35+hD1YIJz0VuBjWL5U= On Thu, 03 Sep 2026 09:21:18 +0200 Gabriele Monaco wrote: > 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 less > > so of any request from people who want this kind of programmability. > > > > 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 and 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 enough > 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-vehicle > OSes like RHIVOS) > > BPF seems the natural tool for the job to me. Mind that RV monitors would be > simple users of BPF, requiring only modifications in the RV subsystem but using > standard BPF facilities. > As RV would simply be a user of BPF and not modifying BPF infrastructure, I'm not so sure you have the jurisdiction to NAK it. It would be like me NAKing how you create a trace event. RV monitors are a very good way to make sure the system is preforming properly. This looks exactly like a perfect use case for using BPF instead of having to install modules. Either BPF is a tool for the kernel or it isn't. You can't judge where BPF gets used. You can only judge on modifications to BFP. -- Steve > I'm totally open to discuss on this though. > > Thanks, > Gabriele > > [1] - https://lore.kernel.org/lkml/20260522125833.264145-1-gmonaco@redhat.com > [2] - https://lore.kernel.org/lkml/20260113085159.114226-3-gmonaco@redhat.com > [3] - > https://lore.kernel.org/linux-rt-users/20260826132153.2476006-1-bigeasy@linutronix.de/T/#t > [4] - > https://lore.kernel.org/lkml/20260827072400.45734-1-tobias.schaffner@siemens.com