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, 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 9B72AC2BA83 for ; Mon, 10 Feb 2020 00:36:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7882E20870 for ; Mon, 10 Feb 2020 00:36:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726944AbgBJAgZ (ORCPT ); Sun, 9 Feb 2020 19:36:25 -0500 Received: from mga03.intel.com ([134.134.136.65]:24790 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725877AbgBJAgY (ORCPT ); Sun, 9 Feb 2020 19:36:24 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 09 Feb 2020 16:36:23 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,423,1574150400"; d="scan'208";a="232948849" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by orsmga003.jf.intel.com with ESMTP; 09 Feb 2020 16:36:21 -0800 Date: Mon, 10 Feb 2020 08:36:39 +0800 From: Wei Yang To: David Hildenbrand Cc: Baoquan He , Wei Yang , Dan Williams , Wei Yang , Andrew Morton , Oscar Salvador , Linux MM , Linux Kernel Mailing List Subject: Re: [PATCH 2/3] mm/sparsemem: get physical address to page struct instead of virtual address to pfn Message-ID: <20200210003639.GD7326@richard> Reply-To: Wei Yang References: <20200209135015.GX8965@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Feb 09, 2020 at 03:14:28PM +0100, David Hildenbrand wrote: > > >> Am 09.02.2020 um 14:50 schrieb Baoquan He : >> >> On 02/07/20 at 11:26am, Wei Yang wrote: >>>> On Thu, Feb 06, 2020 at 06:19:46PM -0800, Dan Williams wrote: >>>> On Thu, Feb 6, 2020 at 3:17 PM Wei Yang wrote: >>>>> >>>>> memmap should be the physical address to page struct instead of virtual >>>>> address to pfn. >>>>> >>>>> Since we call this only for SPARSEMEM_VMEMMAP, pfn_to_page() is valid at >>>>> this point. >>>>> >>>>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") >>>>> Signed-off-by: Wei Yang >>>>> CC: Dan Williams >>>>> --- >>>>> mm/sparse.c | 2 +- >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>> >>>>> diff --git a/mm/sparse.c b/mm/sparse.c >>>>> index b5da121bdd6e..56816f653588 100644 >>>>> --- a/mm/sparse.c >>>>> +++ b/mm/sparse.c >>>>> @@ -888,7 +888,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, >>>>> /* Align memmap to section boundary in the subsection case */ >>>>> if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) && >>>>> section_nr_to_pfn(section_nr) != start_pfn) >>>>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr)); >>>>> + memmap = pfn_to_page(section_nr_to_pfn(section_nr)); >>>> >>>> Yes, this looks obviously correct. This might be tripping up >>>> makedumpfile. Do you see any practical effects of this bug? The kernel >>>> mostly avoids ->section_mem_map in the vmemmap case and in the >>>> !vmemmap case section_nr_to_pfn(section_nr) should always equal >>>> start_pfn. >>> >>> I took another look into the code. Looks there is no practical effect after >>> this. Because in the vmemmap case, we don't need ->section_mem_map to retrieve >>> the real memmap. >>> >>> But leave a inconsistent data in section_mem_map is not a good practice. >> >> Yeah, it does has no pratical effect. I tried to create sub-section >> alighed namespace, then trigger crash, makedumpfile isn't impacted. >> Because pmem memory is only added, but not onlined. We don't report it >> to kdump, makedumpfile will ignore it. >> >> I think it's worth fixing it to encode a correct memmap address. We >> don't know if in the future this will break anything. > >We can have system memory and devmem overlap within a section (which is still buggy and to be fixed in other regard - e.g., pfn_to_online_page() does not work correctly). > >E.g., 64 mb of (boot) system memory in a section. Then you can hot-add devmem that spans the remaining 64 mb of that section. > >So some of that memory will be kdumped - and should be fixed if broken. > >Cheers Thanks for the explanation, I will add this in the changelog. > > >> >> Thanks >> Baoquan -- Wei Yang Help you, Help me