From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3570DC282D7 for ; Tue, 5 Feb 2019 15:43:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 06C09217D6 for ; Tue, 5 Feb 2019 15:43:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="f9WHTPuG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730158AbfBEPnX (ORCPT ); Tue, 5 Feb 2019 10:43:23 -0500 Received: from mail.skyhub.de ([5.9.137.197]:50284 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730116AbfBEPnU (ORCPT ); Tue, 5 Feb 2019 10:43:20 -0500 Received: from zn.tnic (p200300EC2BCB6B00244CCF9C8D56D337.dip0.t-ipconnect.de [IPv6:2003:ec:2bcb:6b00:244c:cf9c:8d56:d337]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id A05A21EC0229; Tue, 5 Feb 2019 16:43:18 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1549381398; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=X1vMKrLb28yWHq2CP/gd/lEJL/Tqn4anOE3PJOAduGM=; b=f9WHTPuGyR8bphc3CXEBOB4VYCooozCl+dg5wvNDCjVT1X/RFaSOnQfxKzi0rfKHKRGe8q qRaYHcmC9Rq9Pc+UBsNXAVDUmXhTIuKn2xCWrjmdGufGEgxZYkJSmhrhh4GDt1sEd8UEtI qTgETlX1ok//bmDq8I/t5M+N7eXs/3k= Date: Tue, 5 Feb 2019 16:43:09 +0100 From: Borislav Petkov To: Dave Hansen Cc: Peter Zijlstra , Thomas Gleixner , Fenghua Yu , Ingo Molnar , H Peter Anvin , Ashok Raj , Michael Chan , Ravi V Shankar , Ricardo Neri , linux-kernel , x86 Subject: Re: [PATCH v3 08/10] x86/setcpuid: Add kernel option setcpuid Message-ID: <20190205154309.GU21801@zn.tnic> References: <1549084491-57808-1-git-send-email-fenghua.yu@intel.com> <1549084491-57808-9-git-send-email-fenghua.yu@intel.com> <9fa7406b-113f-fe0a-9fc7-ef00b3a6b620@intel.com> <20190204195704.GJ29639@zn.tnic> <5c2f0af3-1740-f16b-6ff6-6bec6a325034@intel.com> <20190205084857.GK17528@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 05, 2019 at 07:19:16AM -0800, Dave Hansen wrote: > This is one of the few times that we're pretty confident that folks will > use this. The reason we're going to this trouble is that the split lock > detection is wanted by actual customers, and they want it before it's > implemented on a processor with real enumeration. > > This isn't something we want everybody and their grandma to turn on; > it's a rather specialized feature. It's really only for folks that care > about the latency incurred across the entire system on split lock > operations. ... > It's not for developers. This really is for (somewhat niche) end users > that want split lock detection in production. This is all really an > effort to get them running mainline or real distro kernels. This all sounds to me like it shouldn't even be mainline but in a special, evaluation kernel. If anything, it should be default off and be opted-in by a cmdline switch. None of that *cpuid=* toggling dance. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.