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 019A3C6377A for ; Thu, 22 Jul 2021 00:26:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DC1D560D07 for ; Thu, 22 Jul 2021 00:26:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229927AbhGUXqF (ORCPT ); Wed, 21 Jul 2021 19:46:05 -0400 Received: from mga17.intel.com ([192.55.52.151]:39215 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229600AbhGUXqE (ORCPT ); Wed, 21 Jul 2021 19:46:04 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10052"; a="191814944" X-IronPort-AV: E=Sophos;i="5.84,259,1620716400"; d="scan'208";a="191814944" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Jul 2021 17:26:40 -0700 X-IronPort-AV: E=Sophos;i="5.84,259,1620716400"; d="scan'208";a="501534993" 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; 21 Jul 2021 17:26:36 -0700 From: "Huang, Ying" To: Sean Christopherson Cc: Yang Shi , Zi Yan , Christian Borntraeger , 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> Date: Thu, 22 Jul 2021 08:26:34 +0800 In-Reply-To: (Sean Christopherson's message of "Wed, 21 Jul 2021 15:41:05 +0000") Message-ID: <87lf5z9osl.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 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? Best Regards, Huang, Ying