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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,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 E15DCC433F4 for ; Tue, 28 Aug 2018 00:35:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C0D42084E for ; Tue, 28 Aug 2018 00:35:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8C0D42084E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1726619AbeH1EYU (ORCPT ); Tue, 28 Aug 2018 00:24:20 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:55066 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725724AbeH1EYU (ORCPT ); Tue, 28 Aug 2018 00:24:20 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E085740203F1; Tue, 28 Aug 2018 00:35:19 +0000 (UTC) Received: from redhat.com (ovpn-120-184.rdu2.redhat.com [10.10.120.184]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 55819202704E; Tue, 28 Aug 2018 00:35:19 +0000 (UTC) Date: Mon, 27 Aug 2018 20:35:17 -0400 From: Jerome Glisse To: Zi Yan Cc: linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org, "Aneesh Kumar K . V" , Ralph Campbell , John Hubbard Subject: Re: [PATCH 4/7] mm/hmm: properly handle migration pmd Message-ID: <20180828003517.GA4042@redhat.com> References: <20180824192549.30844-1-jglisse@redhat.com> <20180824192549.30844-5-jglisse@redhat.com> <0560A126-680A-4BAE-8303-F1AB34BE4BA5@cs.rutgers.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0560A126-680A-4BAE-8303-F1AB34BE4BA5@cs.rutgers.edu> User-Agent: Mutt/1.10.0 (2018-05-17) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Tue, 28 Aug 2018 00:35:19 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Tue, 28 Aug 2018 00:35:19 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'jglisse@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 24, 2018 at 08:05:46PM -0400, Zi Yan wrote: > Hi Jérôme, > > On 24 Aug 2018, at 15:25, jglisse@redhat.com wrote: > > > From: Jérôme Glisse > > > > Before this patch migration pmd entry (!pmd_present()) would have > > been treated as a bad entry (pmd_bad() returns true on migration > > pmd entry). The outcome was that device driver would believe that > > the range covered by the pmd was bad and would either SIGBUS or > > simply kill all the device's threads (each device driver decide > > how to react when the device tries to access poisonnous or invalid > > range of memory). > > > > This patch explicitly handle the case of migration pmd entry which > > are non present pmd entry and either wait for the migration to > > finish or report empty range (when device is just trying to pre- > > fill a range of virtual address and thus do not want to wait or > > trigger page fault). > > > > Signed-off-by: Aneesh Kumar K.V > > Signed-off-by: Jérôme Glisse > > Cc: Ralph Campbell > > Cc: John Hubbard > > Cc: Andrew Morton > > --- > > mm/hmm.c | 45 +++++++++++++++++++++++++++++++++++++++------ > > 1 file changed, 39 insertions(+), 6 deletions(-) > > > > diff --git a/mm/hmm.c b/mm/hmm.c > > index a16678d08127..659efc9aada6 100644 > > --- a/mm/hmm.c > > +++ b/mm/hmm.c > > @@ -577,22 +577,47 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, > > { > > struct hmm_vma_walk *hmm_vma_walk = walk->private; > > struct hmm_range *range = hmm_vma_walk->range; > > + struct vm_area_struct *vma = walk->vma; > > uint64_t *pfns = range->pfns; > > unsigned long addr = start, i; > > pte_t *ptep; > > + pmd_t pmd; > > > > - i = (addr - range->start) >> PAGE_SHIFT; > > > > again: > > - if (pmd_none(*pmdp)) > > + pmd = READ_ONCE(*pmdp); > > + if (pmd_none(pmd)) > > return hmm_vma_walk_hole(start, end, walk); > > > > - if (pmd_huge(*pmdp) && (range->vma->vm_flags & VM_HUGETLB)) > > + if (pmd_huge(pmd) && (range->vma->vm_flags & VM_HUGETLB)) > > return hmm_pfns_bad(start, end, walk); > > > > - if (pmd_devmap(*pmdp) || pmd_trans_huge(*pmdp)) { > > - pmd_t pmd; > > + if (!pmd_present(pmd)) { > > + swp_entry_t entry = pmd_to_swp_entry(pmd); > > + > > + if (is_migration_entry(entry)) { > > I think you should check thp_migration_supported() here, since PMD migration is only enabled in x86_64 systems. > Other architectures should treat PMD migration entries as bad. You are right, Andrew do you want to repost or can you edit above if to: if (thp_migration_supported() && is_migration_entry(entry)) { Cheers, Jérôme