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=-8.3 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 3FD8FC35242 for ; Wed, 12 Feb 2020 02:27:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1C16D2082F for ; Wed, 12 Feb 2020 02:27:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727782AbgBLC1x (ORCPT ); Tue, 11 Feb 2020 21:27:53 -0500 Received: from mga04.intel.com ([192.55.52.120]:50742 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727535AbgBLC1x (ORCPT ); Tue, 11 Feb 2020 21:27:53 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Feb 2020 18:27:52 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,428,1574150400"; d="scan'208";a="226715029" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by orsmga008.jf.intel.com with ESMTP; 11 Feb 2020 18:27:50 -0800 Date: Wed, 12 Feb 2020 10:28:08 +0800 From: Wei Yang To: David Hildenbrand Cc: Wei Yang , akpm@linux-foundation.org, osalvador@suse.de, dan.j.williams@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Baoquan He Subject: Re: [Patch v2] mm/sparsemem: get address to page struct instead of address to pfn Message-ID: <20200212022808.GB7855@richard> Reply-To: Wei Yang References: <20200210005048.10437-1-richardw.yang@linux.intel.com> <90742479-cbb1-4ea9-c20c-53a1df34b806@redhat.com> <20200210231623.GC32495@richard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 Tue, Feb 11, 2020 at 03:01:35PM +0100, David Hildenbrand wrote: >On 11.02.20 00:16, Wei Yang wrote: >> On Mon, Feb 10, 2020 at 10:00:47AM +0100, David Hildenbrand wrote: >>> On 10.02.20 01:50, Wei Yang wrote: >>>> memmap should be the address to page struct instead of address to pfn. >>>> >>> >>> "mm/sparsemem: fix wrong address in ms->section_mem_map with sub-sections >>> >>> We want to store the address of the memmap, not the address of the first >>> pfn. >>> >>> E.g., we can have both (boot) system memory and devmem residing in a >>> single section. Once we hot-add the devmem part, the address stored in >>> ms->section_mem_map would be wrong, and kdump would not be able to >>> dump the right memory. >>> " >>> >>> ? See below >>> >>>> As mentioned by David, if system memory and devmem sit within a >>>> section, the mismatch address would lead kdump to dump unexpected >>>> memory. >>>> >>>> Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is >>>> valid to get the page struct address at this point. >>>> >>>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") >>>> Signed-off-by: Wei Yang >>>> CC: Dan Williams >>>> CC: David Hildenbrand >>>> CC: Baoquan He >>>> >>>> --- >>>> v2: >>>> * adjust comment to mention the mismatch data would affect kdump >>>> >>>> --- >>>> mm/sparse.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/mm/sparse.c b/mm/sparse.c >>>> index 586d85662978..4862ec2cfbc0 100644 >>>> --- a/mm/sparse.c >>>> +++ b/mm/sparse.c >>>> @@ -887,7 +887,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, >>>> >>>> /* Align memmap to section boundary in the subsection case */ >>>> if (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)); >>> >>> I think this whole code should be reworked. >>> >>> Callee returns a pointer. Caller: Nah, I know it better. >>> >>> Just nasty. >>> >>> >>> Can we do something like this instead: >>> >>> >>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c >>> index 200aef686722..c5091feef29e 100644 >>> --- a/mm/sparse-vmemmap.c >>> +++ b/mm/sparse-vmemmap.c >>> @@ -266,5 +266,5 @@ struct page * __meminit >>> __populate_section_memmap(unsigned long pfn, >>> if (vmemmap_populate(start, end, nid, altmap)) >>> return NULL; >>> >>> - return pfn_to_page(pfn); >>> + return pfn_to_page(SECTION_ALIGN_DOWN(pfn)); >>> } >>> diff --git a/mm/sparse.c b/mm/sparse.c >>> index c184b69460b7..21902d7931e4 100644 >>> --- a/mm/sparse.c >>> +++ b/mm/sparse.c >>> @@ -788,6 +788,10 @@ static void section_deactivate(unsigned long pfn, >>> unsigned long nr_pages, >>> depopulate_section_memmap(pfn, nr_pages, altmap); >>> } >>> >>> +/* >>> + * Returns the memmap of the first pfn of the section (not of >>> + * sub-sections). >>> + */ >>> static struct page * __meminit section_activate(int nid, unsigned long pfn, >>> unsigned long nr_pages, struct vmem_altmap *altmap) >>> { >>> @@ -882,9 +886,6 @@ int __meminit sparse_add_section(int nid, unsigned >>> long start_pfn, >>> set_section_nid(section_nr, nid); >>> section_mark_present(ms); >>> >>> - /* Align memmap to section boundary in the subsection case */ >>> - if (section_nr_to_pfn(section_nr) != start_pfn) >>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr)); >>> sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0); >>> >>> return 0; >>> >>> >>> Untested, of course :) >> >> I think you get some point. As you mentioned in the following reply, we need >> to adjust poisoning after this change. > >We can just poison after setting up the section (IOW, move it further down). > >> >> This looks like a trade off between two options. I don't have a strong >> preference. > >I clearly prefer if *section*_activate() returns the memmap of the >section. This code is just confusing. But I can send a cleanup on top if >you want to keep it like that for now. > Sure, a cleanup patch may help audience get more understanding about the change. > >-- >Thanks, > >David / dhildenb -- Wei Yang Help you, Help me