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Mon, 10 Feb 2020 09:13:20 +0000 (UTC) Received: from [10.36.117.242] (ovpn-117-242.ams2.redhat.com [10.36.117.242]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8880D89F25; Mon, 10 Feb 2020 09:13:17 +0000 (UTC) Subject: Re: [Patch v2] mm/sparsemem: get address to page struct instead of address to pfn From: David Hildenbrand To: Wei Yang , akpm@linux-foundation.org, osalvador@suse.de, dan.j.williams@intel.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Baoquan He References: <20200210005048.10437-1-richardw.yang@linux.intel.com> <90742479-cbb1-4ea9-c20c-53a1df34b806@redhat.com> Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: <0beb353c-0192-874f-a2c9-f6c575716e25@redhat.com> Date: Mon, 10 Feb 2020 10:13:16 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <90742479-cbb1-4ea9-c20c-53a1df34b806@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10.02.20 10:00, 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 the following would be needed as well with Wei's fix: @@ -876,15 +880,13 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, * Poison uninitialized struct pages in order to catch invalid flags * combinations. */ - page_init_poison(pfn_to_page(start_pfn), sizeof(struct page) * nr_pages); + page_init_poison(memmap + start_pfn - SECTION_ALIGN_DOWN(start_pfn), + sizeof(struct page) * nr_pages); ms = __nr_to_section(section_nr); Or we can simply move the poisoning behind sparse_init_one_section(). -- Thanks, David / dhildenb