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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_SANE_1 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 8FDB5C43141 for ; Thu, 14 Nov 2019 14:40:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 72BAA20718 for ; Thu, 14 Nov 2019 14:40:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726592AbfKNOkd (ORCPT ); Thu, 14 Nov 2019 09:40:33 -0500 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:59432 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726263AbfKNOkd (ORCPT ); Thu, 14 Nov 2019 09:40:33 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R121e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=shile.zhang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0Ti3zzN0_1573742422; Received: from ali-6c96cfdd1403.local(mailfrom:shile.zhang@linux.alibaba.com fp:SMTPD_---0Ti3zzN0_1573742422) by smtp.aliyun-inc.com(127.0.0.1); Thu, 14 Nov 2019 22:40:23 +0800 Subject: Re: [PATCH] mm/vmalloc: Fix regression caused by needless vmalloc_sync_all() To: Michal Hocko Cc: Andrew Morton , Joerg Roedel , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20191113095530.228959-1-shile.zhang@linux.alibaba.com> <20191114135641.GA1356@dhcp22.suse.cz> From: Shile Zhang Message-ID: <83a39694-373b-da16-3be1-22108ace0107@linux.alibaba.com> Date: Thu, 14 Nov 2019 22:40:22 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20191114135641.GA1356@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/11/14 21:56, Michal Hocko wrote: > On Wed 13-11-19 17:55:30, Shile Zhang wrote: >> vmalloc_sync_all() was put in the common path in >> __purge_vmap_area_lazy(), for one sync issue only happened on X86_32 >> with PTI enabled. It is needless for X86_64, which caused a big regression >> in UnixBench Shell8 testing on X86_64. >> Similar regression also reported by 0-day kernel test robot in reaim >> benchmarking: >> https://lists.01.org/hyperkitty/list/lkp@lists.01.org/thread/4D3JPPHBNOSPFK2KEPC6KGKS6J25AIDB/ >> >> Fix it by adding more conditions. > This doesn't really explain a lot. Could you explain why the syncing > should be limited only to PAE and !SHARED_KERNEL_PMD? Thanks for your review! Sorry for that, I'm not clear about the original issue the patch 3f8fd02b1bf1 ("mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()") fixed. I just get that limitation info from the commit log as following: " This is only needed x86-32 with !SHARED_KERNEL_PMD, which is the case on a PAE kernel with PTI enabled. On affected systems the missing sync causes old mappings to persist in some page-tables, causing data corruption and other undefined behavior. " https://patchwork.kernel.org/cover/11050511/ Hi, Joerg Could you please help to recall the original issue you encountered before? Thanks! > >> Fixes: 3f8fd02b1bf1 ("mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()") >> >> Signed-off-by: Shile Zhang >> --- >> mm/vmalloc.c | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >> index a3c70e275f4e..7b9fc7966da6 100644 >> --- a/mm/vmalloc.c >> +++ b/mm/vmalloc.c >> @@ -1255,11 +1255,17 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) >> if (unlikely(valist == NULL)) >> return false; >> >> +#if defined(CONFIG_X86_32) && defined(CONFIG_X86_PAE) >> /* >> * First make sure the mappings are removed from all page-tables >> * before they are freed. >> + * >> + * This is only needed on x86-32 with !SHARED_KERNEL_PMD, which is >> + * the case on a PAE kernel with PTI enabled. >> */ >> - vmalloc_sync_all(); >> + if (!SHARED_KERNEL_PMD && boot_cpu_has(X86_FEATURE_PTI)) >> + vmalloc_sync_all(); >> +#endif >> >> /* >> * TODO: to calculate a flush range without looping. >> -- >> 2.24.0.rc2 >>