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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6A65EC433E0 for ; Thu, 4 Jun 2020 14:39:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 558A92072E for ; Thu, 4 Jun 2020 14:39:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729089AbgFDOjL (ORCPT ); Thu, 4 Jun 2020 10:39:11 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:58339 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728682AbgFDOjK (ORCPT ); Thu, 4 Jun 2020 10:39:10 -0400 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 49d7hB0LCzzB09bC; Thu, 4 Jun 2020 16:39:06 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id HcnqsAQAgwl5; Thu, 4 Jun 2020 16:39:05 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 49d7h96hCgzB09bB; Thu, 4 Jun 2020 16:39:05 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id CFDAC8B8CE; Thu, 4 Jun 2020 16:39:07 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id Sy6zOSmi2CZ5; Thu, 4 Jun 2020 16:39:07 +0200 (CEST) Received: from pc16570vm.idsi0.si.c-s.fr (po15451.idsi0.si.c-s.fr [10.25.210.22]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 620E88B8C9; Thu, 4 Jun 2020 16:39:07 +0200 (CEST) Subject: Re: linux-next: build failure on powerpc 8xx with 16k pages To: Peter Zijlstra , Will Deacon Cc: Andrew Morton , Michael Ellerman , PowerPC , Thomas Gleixner , Stephen Rothwell , Linux Next Mailing List , Linux Kernel Mailing List References: <20200604111723.GA1267@willie-the-truck> <20200604120007.GA4117@hirez.programming.kicks-ass.net> From: Christophe Leroy Message-ID: <1160ea76-729b-60a2-31d6-998c57b77858@csgroup.eu> Date: Thu, 4 Jun 2020 14:35:14 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20200604120007.GA4117@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/04/2020 12:00 PM, Peter Zijlstra wrote: > On Thu, Jun 04, 2020 at 12:17:23PM +0100, Will Deacon wrote: >> Hi, [+Peter] >> >> On Thu, Jun 04, 2020 at 10:48:03AM +0000, Christophe Leroy wrote: >>> Using mpc885_ads_defconfig with CONFIG_PPC_16K_PAGES instead of >>> CONFIG_PPC_4K_PAGES, getting the following build failure: >>> >>> CC mm/gup.o >>> In file included from ./include/linux/kernel.h:11:0, >>> from mm/gup.c:2: >>> In function 'gup_hugepte.constprop', >>> inlined from 'gup_huge_pd.isra.78' at mm/gup.c:2465:8: >>> ./include/linux/compiler.h:392:38: error: call to '__compiletime_assert_257' >>> declared with attribute error: Unsupported access size for >>> {READ,WRITE}_ONCE(). >>> _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) >>> ^ >>> ./include/linux/compiler.h:373:4: note: in definition of macro >>> '__compiletime_assert' >>> prefix ## suffix(); \ >>> ^ >>> ./include/linux/compiler.h:392:2: note: in expansion of macro >>> '_compiletime_assert' >>> _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) >>> ^ >>> ./include/linux/compiler.h:405:2: note: in expansion of macro >>> 'compiletime_assert' >>> compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ >>> ^ >>> ./include/linux/compiler.h:291:2: note: in expansion of macro >>> 'compiletime_assert_rwonce_type' >>> compiletime_assert_rwonce_type(x); \ >>> ^ >>> mm/gup.c:2428:8: note: in expansion of macro 'READ_ONCE' >>> pte = READ_ONCE(*ptep); >>> ^ >>> In function 'gup_get_pte', >>> inlined from 'gup_pte_range' at mm/gup.c:2228:9, >>> inlined from 'gup_pmd_range' at mm/gup.c:2613:15, >>> inlined from 'gup_pud_range' at mm/gup.c:2641:15, >>> inlined from 'gup_p4d_range' at mm/gup.c:2666:15, >>> inlined from 'gup_pgd_range' at mm/gup.c:2694:15, >>> inlined from 'internal_get_user_pages_fast' at mm/gup.c:2785:3: >> >> At first glance, this looks like a real bug in the 16k page code -- you're >> loading the pte non-atomically on the fast GUP path and so you're prone to >> tearing, which probably isn't what you want. For a short-term hack, I'd >> suggest having CONFIG_HAVE_FAST_GUP depend on !CONFIG_PPC_16K_PAGES, but if >> you want to support this them you'll need to rework your pte_t so that it >> can be loaded atomically. > > Looking at commit 55c8fc3f49302, they're all the exact same value, so > what they could do is grow another special gup_get_pte() variant that > just loads the first value. > > Also, per that very same commit, there's a distinct lack of WRITE_ONCE() > in the pte_update() / __set_pte_at() paths for much of Power. > Thanks for the idea. Now I get the same issue at CC mm/mincore.o In file included from ./include/asm-generic/bug.h:5:0, from ./arch/powerpc/include/asm/bug.h:109, from ./include/linux/bug.h:5, from ./include/linux/mmdebug.h:5, from ./include/linux/mm.h:9, from ./include/linux/pagemap.h:8, from mm/mincore.c:11: In function 'huge_ptep_get', inlined from 'mincore_hugetlb' at mm/mincore.c:35:20: ./include/linux/compiler.h:392:38: error: call to '__compiletime_assert_218' declared with attribute error: Unsupported access size for {READ,WRITE}_ONCE(). _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) ^ ./include/linux/compiler.h:373:4: note: in definition of macro '__compiletime_assert' prefix ## suffix(); \ ^ ./include/linux/compiler.h:392:2: note: in expansion of macro '_compiletime_assert' _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) ^ ./include/linux/compiler.h:405:2: note: in expansion of macro 'compiletime_assert' compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \ ^ ./include/linux/compiler.h:291:2: note: in expansion of macro 'compiletime_assert_rwonce_type' compiletime_assert_rwonce_type(x); \ ^ ./include/asm-generic/hugetlb.h:125:9: note: in expansion of macro 'READ_ONCE' return READ_ONCE(*ptep); ^ make[2]: *** [mm/mincore.o] Error 1 I guess for this one I have to implement platform specific huge_ptep_get() Christophe