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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 68623C433E1 for ; Fri, 3 Jul 2020 11:41:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4EC8420772 for ; Fri, 3 Jul 2020 11:41:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726440AbgGCLlm (ORCPT ); Fri, 3 Jul 2020 07:41:42 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:24128 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726112AbgGCLll (ORCPT ); Fri, 3 Jul 2020 07:41:41 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 063BUv1Y000696; Fri, 3 Jul 2020 07:40:46 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 320wmq5k82-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 03 Jul 2020 07:40:46 -0400 Received: from m0098413.ppops.net (m0098413.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 063BWGpg004464; Fri, 3 Jul 2020 07:40:45 -0400 Received: from ppma06ams.nl.ibm.com (66.31.33a9.ip4.static.sl-reverse.com [169.51.49.102]) by mx0b-001b2d01.pphosted.com with ESMTP id 320wmq5k77-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 03 Jul 2020 07:40:45 -0400 Received: from pps.filterd (ppma06ams.nl.ibm.com [127.0.0.1]) by ppma06ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 063BaVop023875; Fri, 3 Jul 2020 11:40:43 GMT Received: from b06avi18878370.portsmouth.uk.ibm.com (b06avi18878370.portsmouth.uk.ibm.com [9.149.26.194]) by ppma06ams.nl.ibm.com with ESMTP id 31wwch6rqn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 03 Jul 2020 11:40:43 +0000 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 063BefcM63570196 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 3 Jul 2020 11:40:41 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7E3B9A405B; Fri, 3 Jul 2020 11:40:41 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7FCE2A405C; Fri, 3 Jul 2020 11:40:39 +0000 (GMT) Received: from linux.ibm.com (unknown [9.148.204.195]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Fri, 3 Jul 2020 11:40:39 +0000 (GMT) Date: Fri, 3 Jul 2020 14:40:37 +0300 From: Mike Rapoport To: Abhishek Bhardwaj Cc: Anthony Steinhauser , LKML , Waiman Long , Borislav Petkov , "H. Peter Anvin" , Ingo Molnar , Jim Mattson , Joerg Roedel , Josh Poimboeuf , Mark Gross , Paolo Bonzini , Pawan Gupta , Peter Zijlstra , Sean Christopherson , Thomas Gleixner , Tony Luck , Vitaly Kuznetsov , Wanpeng Li , kvm@vger.kernel.org, x86 , Doug Anderson Subject: Re: [PATCH v3] x86/speculation/l1tf: Add KConfig for setting the L1D cache flush mode Message-ID: <20200703114037.GD2999146@linux.ibm.com> References: <20200702221237.2517080-1-abhishekbh@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-07-03_03:2020-07-02,2020-07-03 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 impostorscore=0 adultscore=0 cotscore=-2147483648 suspectscore=1 phishscore=0 priorityscore=1501 mlxscore=0 spamscore=0 bulkscore=0 mlxlogscore=999 lowpriorityscore=0 clxscore=1011 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2007030078 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Jul 02, 2020 at 11:43:47PM -0700, Abhishek Bhardwaj wrote: > We have tried to steer away from kernel command line args for a few reasons. > > I am paraphrasing my colleague Doug's argument here (CC'ed him as well) - > > - The command line args are getting unwieldy. Kernel command line > parameters are not a scalable way to set kernel config. It's intended > as a super limited way for the bootloader to pass info to the kernel > and also as a way for end users who are not compiling the kernel > themselves to tweak kernel behavior. Why cannot you simply add this option to CONFIG_CMDLINE at your kernel build scripts? > - Also, we know we want this setting from the start. This is a > definite smell that it deserves to be a compile time thing rather than > adding extra code + whatever miniscule time at runtime to pass an > extra arg. This might be a compile time thing in your environment, but not necessarily it must be the same in others. For instance, what option should distro kernels select? > I think this was what CONFIGS were intended for. I'm happy to add all > this to the commit message once it's approved in spirit by the > maintainers. > > On Thu, Jul 2, 2020 at 8:18 PM Anthony Steinhauser > wrote: > > > > Yes, this probably requires an explanation why the change is necessary > > or useful. Without that it is difficult to give some meaningful > > feedback. > > > > -- > Abhishek -- Sincerely yours, Mike.