From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753468AbcB2SVI (ORCPT ); Mon, 29 Feb 2016 13:21:08 -0500 Received: from mail.skyhub.de ([78.46.96.112]:45313 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751298AbcB2SVD (ORCPT ); Mon, 29 Feb 2016 13:21:03 -0500 Date: Mon, 29 Feb 2016 19:20:47 +0100 From: Borislav Petkov To: George Spelvin Cc: mcfadden8@llnl.gov, a.p.zijlstra@chello.nl, acme@infradead.org, ak@linux.intel.com, andriy.shevchenko@linux.intel.com, brgerst@gmail.com, dan.j.williams@intel.com, dyoung@redhat.com, hpa@zytor.com, jolsa@redhat.com, linux-kernel@vger.kernel.org, luto@kernel.org, mingo@kernel.org, mingo@redhat.com, pavel@ucw.cz, tglx@linutronix.de, viro@zeniv.linux.org.uk, x86@kernel.org, yu.c.chen@intel.com Subject: Re: [PATCH 0/4] MSR: MSR: MSR Whitelist and Batch Introduction Message-ID: <20160229182047.GD3724@pd.tnic> References: <20160229145859.GA3724@pd.tnic> <20160229175318.14183.qmail@ns.horizon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20160229175318.14183.qmail@ns.horizon.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 29, 2016 at 12:53:18PM -0500, George Spelvin wrote: > I worry that this is this too ambitious a goal. Who is volunteering > to actually do this? >>From a quick look, the stuff in the examples was already in the rapl driver. > It takes quite a while to find a good OS-level abstraction (remember > wakelocks?), and MSRs are the CPU architect's equivalent of ioctls. > So they're a bit of a mess, and there will keep being new ones. And yet you end up needing only a handful in most cases. > I agree with you about anything that's going to see widespread use, but > for specialized (apparently mostly HPC) use where the application really > is heavily optimized for specific CPU models, perhaps dangerous-but-simple > is good enough? If it is that specialized, then it doesn't belong upstream. > The proposed interface is simple and imposes very little maintenance > burden on the kernel. My main objection is that it's yet another > special-case permission system. Are we *sure* we'll never want to have > to classes of users with different access rights? The proposed interface is the wrong thing to do. There's no need to talk about how simple and less of a burden it is. The burden comes when people start complaining about strange issues and we go and have to get a full MSR dump at the time the explosion happens because some userspace tool went nuts and scribbled all over them. No one wants to be on the receiving end of a bug report like this. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply.