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=-3.8 required=3.0 tests=BAYES_00, 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 84905C4320A for ; Thu, 22 Jul 2021 23:10:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63A7460EB2 for ; Thu, 22 Jul 2021 23:10:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232599AbhGVW3p (ORCPT ); Thu, 22 Jul 2021 18:29:45 -0400 Received: from mga11.intel.com ([192.55.52.93]:23079 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232024AbhGVW3o (ORCPT ); Thu, 22 Jul 2021 18:29:44 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10053"; a="208656082" X-IronPort-AV: E=Sophos;i="5.84,262,1620716400"; d="scan'208";a="208656082" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jul 2021 16:10:17 -0700 X-IronPort-AV: E=Sophos;i="5.84,262,1620716400"; d="scan'208";a="502084173" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.239.159.119]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jul 2021 16:10:13 -0700 From: "Huang, Ying" To: Christian Borntraeger Cc: Sean Christopherson , Yang Shi , Zi Yan , Andrew Morton , Linux MM , Linux Kernel Mailing List , Dan Carpenter , Mel Gorman , Gerald Schaefer , Heiko Carstens , Hugh Dickins , Andrea Arcangeli , "Kirill A . Shutemov" , Michal Hocko , Vasily Gorbik , Paolo Bonzini , kvm list Subject: Re: [PATCH] mm,do_huge_pmd_numa_page: remove unnecessary TLB flushing code References: <20210720065529.716031-1-ying.huang@intel.com> <0D75A92F-E2AA-480C-9E9A-0B6EE7897757@nvidia.com> <87lf5z9osl.fsf@yhuang6-desk2.ccr.corp.intel.com> <572f1ddd-9ac6-fb09-9a24-1c667dbd1d03@de.ibm.com> Date: Fri, 23 Jul 2021 07:10:12 +0800 In-Reply-To: <572f1ddd-9ac6-fb09-9a24-1c667dbd1d03@de.ibm.com> (Christian Borntraeger's message of "Thu, 22 Jul 2021 09:36:07 +0200") Message-ID: <87czra9c8b.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christian Borntraeger writes: > On 22.07.21 02:26, Huang, Ying wrote: >> Sean Christopherson writes: >>>> >>>> Thanks, I think you are correct. By looking into commit 7066f0f933a1 >>>> ("mm: thp: fix mmu_notifier in migrate_misplaced_transhuge_page()"), >>>> the tlb flush and mmu notifier invalidate were needed since the old >>>> numa fault implementation didn't change PTE to migration entry so it >>>> may cause data corruption due to the writes from GPU secondary MMU. >>>> >>>> The refactor does use the generic migration code which converts PTE to >>>> migration entry before copying data to the new page. >>> >>> That's my understanding as well, based on this blurb from commit 7066f0f933a1. >>> >>> The standard PAGE_SIZEd migrate_misplaced_page is less accelerated and >>> uses the generic migrate_pages which transitions the pte from >>> numa/protnone to a migration entry in try_to_unmap_one() and flushes TLBs >>> and all mmu notifiers there before copying the page. >>> >>> That analysis/justification for removing the invalidate_range() call should be >>> captured in the changelog. Confirmation from Andrea would be a nice bonus. >> When we flush CPU TLB for a page that may be shared with device/VM >> TLB, >> we will call MMU notifiers for the page to flush the device/VM TLB. >> Right? So when we replaced CPU TLB flushing in do_huge_pmd_numa_page() >> with that in try_to_migrate_one(), we will replace the MMU notifiers >> calling too. Do you agree? > > Can someone write an updated commit messages that contains this information? OK. I will update the patch description to add MMU notifiers description. Best Regards, Huang, Ying