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=-2.5 required=3.0 tests=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 6D8A1C43142 for ; Mon, 25 Jun 2018 17:53:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1096325FDB for ; Mon, 25 Jun 2018 17:53:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1096325FDB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964848AbeFYRxR (ORCPT ); Mon, 25 Jun 2018 13:53:17 -0400 Received: from mx2.suse.de ([195.135.220.15]:47759 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934849AbeFYRxQ (ORCPT ); Mon, 25 Jun 2018 13:53:16 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext-too.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 09D56AE90; Mon, 25 Jun 2018 17:53:15 +0000 (UTC) Date: Mon, 25 Jun 2018 19:53:12 +0200 From: Michal Hocko To: "Kani, Toshi" Cc: "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "x86@kernel.org" , "akpm@linux-foundation.org" , "hpa@zytor.com" , "mingo@redhat.com" , "linux-arm-kernel@lists.infradead.org" , "cpandya@codeaurora.org" Subject: Re: [PATCH v3 0/3] fix free pmd/pte page handlings on x86 Message-ID: <20180625175225.GQ28965@dhcp22.suse.cz> References: <20180516233207.1580-1-toshi.kani@hpe.com> <1529938470.14039.134.camel@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1529938470.14039.134.camel@hpe.com> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 25-06-18 14:56:26, Kani Toshimitsu wrote: > On Sun, 2018-06-24 at 15:19 +0200, Thomas Gleixner wrote: > > On Wed, 16 May 2018, Toshi Kani wrote: > > > > > This series fixes two issues in the x86 ioremap free page handlings > > > for pud/pmd mappings. > > > > > > Patch 01 fixes BUG_ON on x86-PAE reported by Joerg. It disables > > > the free page handling on x86-PAE. > > > > > > Patch 02-03 fixes a possible issue with speculation which can cause > > > stale page-directory cache. > > > - Patch 02 is from Chintan's v9 01/04 patch [1], which adds a new arg > > > 'addr', with my merge change to patch 01. > > > - Patch 03 adds a TLB purge (INVLPG) to purge page-structure caches > > > that may be cached by speculation. See the patch descriptions for > > > more detal. > > > > Toshi, Joerg, Michal! > > Hi Thomas, > > Thanks for checking. I was about to ping as well. > > > I'm failing to find a conclusion of this discussion. Can we finally make > > some progress with that? > > I have not heard from Joerg since I last replied to his comments to > Patch 3/3 -- I did my best to explain that there was no issue in the > single page allocation in pud_free_pmd_page(). From my perspective, the > v3 series is good to go. Well, I admit that this not my area but I agree with Joerg that allocating memory inside afunction that is supposed to free page table is far from ideal. More so that the allocation is hardcoded GFP_KERNEL. We already have this antipattern in functions to allocate page tables and it has turned to be maintenance PITA longterm. So if there is a way around that then I would strongly suggest finding a different solution. Whether that is sufficient to ditch the whole series is not my call though. -- Michal Hocko SUSE Labs