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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT 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 7C5F3C43387 for ; Wed, 9 Jan 2019 08:48:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 56A992075C for ; Wed, 9 Jan 2019 08:48:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730042AbfAIIsn (ORCPT ); Wed, 9 Jan 2019 03:48:43 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:53223 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727387AbfAIIsn (ORCPT ); Wed, 9 Jan 2019 03:48:43 -0500 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1gh9XS-0000Yw-9W; Wed, 09 Jan 2019 09:48:38 +0100 Date: Wed, 9 Jan 2019 09:48:38 +0100 From: Sebastian Andrzej Siewior To: Scott Wood Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Steven Rostedt , stable-rt@vger.kernel.org Subject: Re: [PATCH RT] x86/mm/pat: disable preemption __split_large_page() after spin_lock() Message-ID: <20190109084837.yxj6f2aigdkafgkh@linutronix.de> References: <20181213164430.mggilzfjgr5retz6@linutronix.de> <1546994355.3632.15.camel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1546994355.3632.15.camel@redhat.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019-01-08 18:39:15 [-0600], Scott Wood wrote: > On Thu, 2018-12-13 at 17:44 +0100, Sebastian Andrzej Siewior wrote: > > Commit "x86/mm/pat: Disable preemption around __flush_tlb_all()" added a > > warning if __flush_tlb_all() is invoked in preemptible context. On !RT > > the warning does not trigger because a spin lock is acquired which > > disables preemption. On RT the spin lock does not disable preemption and > > so the warning is seen. > > > > Disable preemption to avoid the warning in __flush_tlb_all(). > > > > Signed-off-by: Sebastian Andrzej Siewior > > FWIW, that __flush_tlb_all() can probably just be removed. It was added as > a partial workaround for an erratum, but since it didn't completely solve > the problem, hugepages were disabled on the affected chips in commit > 7a0fc404ae66377 ("x86: Disable large pages on CPUs with Atom erratum > AAE44"). I was going to send a (non-RT) patch removing the flush but in > 4.20 commit c0a759abf5a68 ("x86/mm/cpa: Move flush_tlb_all()") reworked the > code to make it moot. Let me make a note for next major version. > -Scott Sebastian