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[209.132.180.67]) by mx.google.com with ESMTP id k20si768675oiw.273.2020.02.10.15.16.19; Mon, 10 Feb 2020 15:16:32 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727505AbgBJXQH (ORCPT + 99 others); Mon, 10 Feb 2020 18:16:07 -0500 Received: from mga18.intel.com ([134.134.136.126]:47537 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727422AbgBJXQH (ORCPT ); Mon, 10 Feb 2020 18:16:07 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Feb 2020 15:16:06 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,426,1574150400"; d="scan'208";a="227328311" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga008.fm.intel.com with ESMTP; 10 Feb 2020 15:16:05 -0800 Date: Tue, 11 Feb 2020 07:16:23 +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: <20200210231623.GC32495@richard> Reply-To: Wei Yang References: <20200210005048.10437-1-richardw.yang@linux.intel.com> <90742479-cbb1-4ea9-c20c-53a1df34b806@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <90742479-cbb1-4ea9-c20c-53a1df34b806@redhat.com> 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 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. This looks like a trade off between two options. I don't have a strong preference. > >-- >Thanks, > >David / dhildenb -- Wei Yang Help you, Help me