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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY 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 75DA5C433E0 for ; Fri, 3 Jul 2020 08:33:40 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 37DBD207FF for ; Fri, 3 Jul 2020 08:33:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 37DBD207FF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D5DA38D0063; Fri, 3 Jul 2020 04:33:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D0CCA8D005E; Fri, 3 Jul 2020 04:33:39 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C4AD48D0063; Fri, 3 Jul 2020 04:33:39 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0008.hostedemail.com [216.40.44.8]) by kanga.kvack.org (Postfix) with ESMTP id AF8FD8D005E for ; Fri, 3 Jul 2020 04:33:39 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 6A09C181AC9C6 for ; Fri, 3 Jul 2020 08:33:39 +0000 (UTC) X-FDA: 76996100958.08.pen89_2f065ba26e90 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id 480B71819E766 for ; Fri, 3 Jul 2020 08:33:39 +0000 (UTC) X-HE-Tag: pen89_2f065ba26e90 X-Filterd-Recvd-Size: 7830 Received: from out30-44.freemail.mail.aliyun.com (out30-44.freemail.mail.aliyun.com [115.124.30.44]) by imf10.hostedemail.com (Postfix) with ESMTP for ; Fri, 3 Jul 2020 08:33:37 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07425;MF=richard.weiyang@linux.alibaba.com;NM=1;PH=DS;RN=13;SR=0;TI=SMTPD_---0U1YpQ-n_1593765212; Received: from localhost(mailfrom:richard.weiyang@linux.alibaba.com fp:SMTPD_---0U1YpQ-n_1593765212) by smtp.aliyun-inc.com(127.0.0.1); Fri, 03 Jul 2020 16:33:32 +0800 Date: Fri, 3 Jul 2020 16:33:32 +0800 From: Wei Yang To: David Hildenbrand Cc: Wei Yang , 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 Subject: Re: [PATCH] mm: define pte_add_end for consistency Message-ID: <20200703083332.GA17076@L-31X9LVDL-1304.local> Reply-To: Wei Yang 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> <14e6a073-0a8c-3827-4d6f-072d08fbd6cc@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <14e6a073-0a8c-3827-4d6f-072d08fbd6cc@redhat.com> X-Rspamd-Queue-Id: 480B71819E766 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 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 Fri, Jul 03, 2020 at 09:23:30AM +0200, David Hildenbrand wrote: >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. > Actually, I don't get what you are trying to do. So go ahead, maybe I can review your change. >-- >Thanks, > >David / dhildenb -- Wei Yang Help you, Help me