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Mon, 17 Feb 2020 10:38:19 +0000 (UTC) Received: from [10.36.117.64] (ovpn-117-64.ams2.redhat.com [10.36.117.64]) by smtp.corp.redhat.com (Postfix) with ESMTP id 42BC9100164D; Mon, 17 Feb 2020 10:38:14 +0000 (UTC) Subject: Re: [Bug 206401] kernel panic on Hyper-V after 5 minutes due to memory hot-add To: Baoquan He Cc: kkabe@vega.pgw.jp, Oscar Salvador , bugzilla-daemon@bugzilla.kernel.org, akpm@linux-foundation.org, richardw.yang@linux.intel.com, mhocko@kernel.org, n-horiguchi@ah.jp.nec.com, linux-mm@kvack.org References: <20200212073123.GG8965@MiWiFi-R3L-srv> <200217144627.M0113305@vega.pgw.jp> <20200217093447.GA1139@linux> <20200217101318.GL26758@MiWiFi-R3L-srv> <383e5dbf-b402-575d-8dae-5e92b51e9834@redhat.com> <20200217103347.GM26758@MiWiFi-R3L-srv> From: David Hildenbrand 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: Date: Mon, 17 Feb 2020 11:38:13 +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: <20200217103347.GM26758@MiWiFi-R3L-srv> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-MC-Unique: IDNyu-jTMEmzWQo1TsBm7A-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit 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 17.02.20 11:33, Baoquan He wrote: > On 02/17/20 at 11:24am, David Hildenbrand wrote: >> On 17.02.20 11:13, Baoquan He wrote: >>> On 02/17/20 at 10:34am, Oscar Salvador wrote: >>>> On Mon, Feb 17, 2020 at 02:46:27PM +0900, kkabe@vega.pgw.jp wrote: >>>>> =========================================== >>>>> struct page * __meminit populate_section_memmap(unsigned long pfn, >>>>> unsigned long nr_pages, int nid, struct vmem_altmap *altmap) >>>>> { >>>>> struct page *page, *ret; >>>>> unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION; >>>>> >>>>> page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size)); >>>>> if (page) { >>>>> goto got_map_page; >>>>> } >>>>> pr_info("%s: alloc_pages() returned 0x%p (should be 0), reverting to vmalloc(memmap_size=%lu)\n", __func__, page, memmap_size); >>>>> BUG_ON(page != 0); >>>>> >>>>> ret = vmalloc(memmap_size); >>>>> pr_info("%s: vmalloc(%lu) returned 0x%p\n", __func__, memmap_size, ret); >>>>> if (ret) { >>>>> goto got_map_ptr; >>>>> } >>>>> >>>>> return NULL; >>>>> got_map_page: >>>>> ret = (struct page *)pfn_to_kaddr(page_to_pfn(page)); >>>>> pr_info("%s: allocated struct page *page=0x%p\n", __func__, page); >>>>> got_map_ptr: >>>>> >>>>> pr_info("%s: returning struct page * =0x%p\n", __func__, ret); >>>>> return ret; >>>>> } >>>> >>>> Could you please replace %p with %px. Wih the first, pointers are hashed so it is trickier >>>> to get an overview of the meaning. >>>> >>>> David could be right about ZONE_NORMAL vs ZONE_HIGHMEM. >>>> IIUC, default_kernel_zone_for_pfn and default_zone_for_pfn seem to only deal with >>>> (ZONE_DMA,ZONE_NORMAL] or ZONE_MOVABLE. >>> >>> Ah, I think you both have spotted the problem. >>> >>> In i386, if w/o momory hot add, normal memory will only include those >>> below 896M and they are added into normal zone. The left are added into >>> highmem zone. >>> >>> How this influence the page allocation? >>> >>> Very huge. As we know, in i386, normal memory can be accessed with >>> virt_to_phys, namely PAGE_OFFSET + phys. But highmem has to be accessed >>> with kmap. However, the later hot added memory are all put into normal >>> memmory, accessing into them will stump into vmalloc area, I would say. >>> >>> So, i386 doesn't support memory hot add well. Not sure if below change >>> can make it work normally. >>> >>> We can just adjus the hot adding code as we have done for boot memmory. >>> Iterate zone from highmem if allowed when hot add memory. >>> >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index 475d0d68a32c..1380392d9ef5 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -716,7 +716,10 @@ static struct zone *default_kernel_zone_for_pfn(int nid, unsigned long start_pfn >>> struct pglist_data *pgdat = NODE_DATA(nid); >>> int zid; >>> >>> - for (zid = 0; zid <= ZONE_NORMAL; zid++) { >>> + for (zid = 0; zid < MAX_NR_ZONES; zid++) { >> >> ZONE_DEVICE? :/ > > Not sure if ZONE_DEVICE will be supported on 32 bit system. > > >> >>> + if (zid == ZONE_MOVABLE) >>> + continue; >>> + >>> struct zone *zone = &pgdat->node_zones[zid]; >>> >>> if (zone_intersects(zone, start_pfn, nr_pages)) >>> >>> >> >> What if somebody onlines memory from user space explicitly to the normal >> zone? We can trigger crashes? > > Seems the current i386 code doesn't support it. Unless we change that > too. If not reserving virtual address space, later added any memory has > to be highmem. > >> >> This doesn't look like it ever worked reliably, can we just disable >> memory hotplug in case we have PAE? (especially, as continued i386 >> support is questionable) > > This is not PAE, this is only HIGHMEM4G. > Ah, okay. Anyhow, highmem combined with hotplug seems to be in a questionable state. I'd vote for disabling it if possible. -- Thanks, David / dhildenb