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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 5FBE5C433E0 for ; Fri, 3 Jul 2020 07:23:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1327920720 for ; Fri, 3 Jul 2020 07:23:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Dr4MWrby" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1327920720 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 587A38D0059; Fri, 3 Jul 2020 03:23:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 538A56B0010; Fri, 3 Jul 2020 03:23:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3D9318D0059; Fri, 3 Jul 2020 03:23:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0226.hostedemail.com [216.40.44.226]) by kanga.kvack.org (Postfix) with ESMTP id 244D56B000E for ; Fri, 3 Jul 2020 03:23:40 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id DDB55824556B for ; Fri, 3 Jul 2020 07:23:39 +0000 (UTC) X-FDA: 76995924558.26.legs27_330e0d426e90 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin26.hostedemail.com (Postfix) with ESMTP id AAA6B1804B65A for ; Fri, 3 Jul 2020 07:23:39 +0000 (UTC) X-HE-Tag: legs27_330e0d426e90 X-Filterd-Recvd-Size: 11630 Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [207.211.31.120]) by imf25.hostedemail.com (Postfix) with ESMTP for ; Fri, 3 Jul 2020 07:23:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593761018; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=9IrB0nwoPQg3scxw1qShp/wCtwnU4uLcL7itN2Vnaqw=; b=Dr4MWrbyCHuZMVy/2Z6SBH0c6/eJaQkscoyxCyGAPUrkx8bH8SK8s7qybJpm7/P21b3ygz x/SEidaHexGXMZ3ZVBMDEgDJkQNODlXJAPnFqzkyY+zAAK8ZLMFSPyza3u4LgfbxLfyQ5/ VBSbdUs22IKuO6kbNq60qY+7zpRCgqc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-433-EbZGAn7VMRCA21lz1n8nmw-1; Fri, 03 Jul 2020 03:23:36 -0400 X-MC-Unique: EbZGAn7VMRCA21lz1n8nmw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EB035107ACF6; Fri, 3 Jul 2020 07:23:33 +0000 (UTC) Received: from [10.36.114.0] (ovpn-114-0.ams2.redhat.com [10.36.114.0]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1515010013D9; Fri, 3 Jul 2020 07:23:30 +0000 (UTC) Subject: Re: [PATCH] mm: define pte_add_end for consistency To: Wei Yang Cc: dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, akpm@linux-foundation.org, x86@kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org References: <20200630031852.45383-1-richard.weiyang@linux.alibaba.com> <40362e99-a354-c44f-8645-e2326a6df680@redhat.com> <20200701021113.GA51306@L-31X9LVDL-1304.local> <20200701115441.GA4979@L-31X9LVDL-1304.local> <7562991b-c1e7-4037-a3f0-124acd0669b7@redhat.com> <20200703013435.GA11340@L-31X9LVDL-1304.local> 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: <14e6a073-0a8c-3827-4d6f-072d08fbd6cc@redhat.com> Date: Fri, 3 Jul 2020 09:23:30 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200703013435.GA11340@L-31X9LVDL-1304.local> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Rspamd-Queue-Id: AAA6B1804B65A X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 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 03.07.20 03:34, Wei Yang wrote: > On Thu, Jul 02, 2020 at 06:28:19PM +0200, David Hildenbrand wrote: >> On 01.07.20 13:54, Wei Yang wrote: >>> On Wed, Jul 01, 2020 at 10:29:08AM +0200, David Hildenbrand wrote: >>>> On 01.07.20 04:11, Wei Yang wrote: >>>>> On Tue, Jun 30, 2020 at 02:44:00PM +0200, David Hildenbrand wrote: >>>>>> On 30.06.20 05:18, Wei Yang wrote: >>>>>>> When walking page tables, we define several helpers to get the address of >>>>>>> the next boundary. But we don't have one for pte level. >>>>>>> >>>>>>> Let's define it and consolidate the code in several places. >>>>>>> >>>>>>> Signed-off-by: Wei Yang >>>>>>> --- >>>>>>> arch/x86/mm/init_64.c | 6 ++---- >>>>>>> include/linux/pgtable.h | 7 +++++++ >>>>>>> mm/kasan/init.c | 4 +--- >>>>>>> 3 files changed, 10 insertions(+), 7 deletions(-) >>>>>>> >>>>>>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c >>>>>>> index dbae185511cd..f902fbd17f27 100644 >>>>>>> --- a/arch/x86/mm/init_64.c >>>>>>> +++ b/arch/x86/mm/init_64.c >>>>>>> @@ -973,9 +973,7 @@ remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end, >>>>>>> >>>>>>> pte = pte_start + pte_index(addr); >>>>>>> for (; addr < end; addr = next, pte++) { >>>>>>> - next = (addr + PAGE_SIZE) & PAGE_MASK; >>>>>>> - if (next > end) >>>>>>> - next = end; >>>>>>> + next = pte_addr_end(addr, end); >>>>>>> >>>>>>> if (!pte_present(*pte)) >>>>>>> continue; >>>>>>> @@ -1558,7 +1556,7 @@ void register_page_bootmem_memmap(unsigned long section_nr, >>>>>>> get_page_bootmem(section_nr, pud_page(*pud), MIX_SECTION_INFO); >>>>>>> >>>>>>> if (!boot_cpu_has(X86_FEATURE_PSE)) { >>>>>>> - next = (addr + PAGE_SIZE) & PAGE_MASK; >>>>>>> + next = pte_addr_end(addr, end); >>>>>>> pmd = pmd_offset(pud, addr); >>>>>>> if (pmd_none(*pmd)) >>>>>>> continue; >>>>>>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >>>>>>> index 32b6c52d41b9..0de09c6c89d2 100644 >>>>>>> --- a/include/linux/pgtable.h >>>>>>> +++ b/include/linux/pgtable.h >>>>>>> @@ -706,6 +706,13 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) >>>>>>> }) >>>>>>> #endif >>>>>>> >>>>>>> +#ifndef pte_addr_end >>>>>>> +#define pte_addr_end(addr, end) \ >>>>>>> +({ unsigned long __boundary = ((addr) + PAGE_SIZE) & PAGE_MASK; \ >>>>>>> + (__boundary - 1 < (end) - 1) ? __boundary : (end); \ >>>>>>> +}) >>>>>>> +#endif >>>>>>> + >>>>>>> /* >>>>>>> * When walking page tables, we usually want to skip any p?d_none entries; >>>>>>> * and any p?d_bad entries - reporting the error before resetting to none. >>>>>>> diff --git a/mm/kasan/init.c b/mm/kasan/init.c >>>>>>> index fe6be0be1f76..89f748601f74 100644 >>>>>>> --- a/mm/kasan/init.c >>>>>>> +++ b/mm/kasan/init.c >>>>>>> @@ -349,9 +349,7 @@ static void kasan_remove_pte_table(pte_t *pte, unsigned long addr, >>>>>>> unsigned long next; >>>>>>> >>>>>>> for (; addr < end; addr = next, pte++) { >>>>>>> - next = (addr + PAGE_SIZE) & PAGE_MASK; >>>>>>> - if (next > end) >>>>>>> - next = end; >>>>>>> + next = pte_addr_end(addr, end); >>>>>>> >>>>>>> if (!pte_present(*pte)) >>>>>>> continue; >>>>>>> >>>>>> >>>>>> I'm not really a friend of this I have to say. We're simply iterating >>>>>> over single pages, not much magic .... >>>>> >>>>> Hmm... yes, we are iterating on Page boundary, while we many have the case >>>>> when addr or end is not PAGE_ALIGN. >>>> >>>> I really do wonder if not having page aligned addresses actually happens >>>> in real life. Page tables operate on page granularity, and >>>> adding/removing unaligned parts feels wrong ... and that's also why I >>>> dislike such a helper. >>>> >>>> 1. kasan_add_zero_shadow()/kasan_remove_zero_shadow(). If I understand >>>> the logic (WARN_ON()) correctly, we bail out in case we would ever end >>>> up in such a scenario, where we would want to add/remove things not >>>> aligned to PAGE_SIZE. >>>> >>>> 2. remove_pagetable()...->remove_pte_table() >>>> >>>> vmemmap_free() should never try to de-populate sub-pages. Even with >>>> sub-section hot-add/remove (2MB / 512 pages), with valid struct page >>>> sizes (56, 64, 72, 80), we always end up with full pages. >>>> >>>> kernel_physical_mapping_remove() is only called via >>>> arch_remove_memory(). That will never remove unaligned parts. >>>> >>> >>> I don't have a very clear mind now, while when you look into >>> remove_pte_table(), it has two cases based on alignment of addr and next. >>> >>> If we always remove a page, the second case won't happen? >> >> So, the code talks about that the second case can only happen for >> vmemmap, never for direct mappings. >> >> I don't see a way how this could ever happen with current page sizes, >> even with sub-section hotadd (2MB). Maybe that is a legacy leftover or >> was never relevant? Or I am missing something important, where we could >> have sub-4k-page vmemmap data. >> > > I took a calculation on the sub-section page struct size, it is page size (4K) > aligned. This means you are right, which we won't depopulate a sub-page. > > And yes, I am not sure all those variants would fit this case. So I would like > to leave as it now. How about your opinion? I'd say we clean this up and protect it by WARN_ON_ONCE(). Then, it won't need another round of investigation to find out that handling sub-pages is irrelevant. If you don't want to tackle this, I can have a look. Just let me know. -- Thanks, David / dhildenb