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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 19AFFC56201 for ; Thu, 19 Nov 2020 08:46:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 619F722253 for ; Thu, 19 Nov 2020 08:46:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 619F722253 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BC7AC6B006C; Thu, 19 Nov 2020 03:46:06 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B52046B0070; Thu, 19 Nov 2020 03:46:06 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A179B6B0071; Thu, 19 Nov 2020 03:46:06 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0195.hostedemail.com [216.40.44.195]) by kanga.kvack.org (Postfix) with ESMTP id 67CA36B006C for ; Thu, 19 Nov 2020 03:46:06 -0500 (EST) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 0C2E13638 for ; Thu, 19 Nov 2020 08:46:06 +0000 (UTC) X-FDA: 77500535532.23.oven03_1b15b7227341 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin23.hostedemail.com (Postfix) with ESMTP id EDAB837604 for ; Thu, 19 Nov 2020 08:46:05 +0000 (UTC) X-HE-Tag: oven03_1b15b7227341 X-Filterd-Recvd-Size: 2297 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf15.hostedemail.com (Postfix) with ESMTP for ; Thu, 19 Nov 2020 08:46:05 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 398D9AD2B; Thu, 19 Nov 2020 08:46:04 +0000 (UTC) Date: Thu, 19 Nov 2020 08:46:01 +0000 From: Mel Gorman To: Linus Torvalds Cc: Thomas Gleixner , LKML , the arch/x86 maintainers , Christoph Hellwig , Matthew Wilcox , Daniel Vetter , Andrew Morton , Linux-MM , Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Daniel Bristot de Oliveira Subject: Re: [patch V4 2/8] mm/highmem: Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP Message-ID: <20201119084601.GG3306@suse.de> References: <20201118194838.753436396@linutronix.de> <20201118204007.028261233@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Nov 18, 2020 at 01:13:57PM -0800, Linus Torvalds wrote: > On Wed, Nov 18, 2020 at 12:58 PM Thomas Gleixner wrote: > > > > Provide CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP which forces the temporary > > mapping even for lowmem pages. This needs to be a seperate config switch > > because this only works on architectures which do not have cache aliasing > > problems. > > Very good. And you made sure to have a comment to not enable it for > production systems. > > Hopefully people will even read it ;) > And not start thinking it as a security hardening option. -- Mel Gorman SUSE Labs