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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 7ADF5C4CECE for ; Wed, 18 Sep 2019 16:26:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 47DAF20578 for ; Wed, 18 Sep 2019 16:26:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="pyjpbDaw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728334AbfIRQ0N (ORCPT ); Wed, 18 Sep 2019 12:26:13 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:45353 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726900AbfIRQ0M (ORCPT ); Wed, 18 Sep 2019 12:26:12 -0400 Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 46YQMh22Z3z9v1BX; Wed, 18 Sep 2019 18:26:08 +0200 (CEST) Authentication-Results: localhost; dkim=pass reason="1024-bit key; insecure key" header.d=c-s.fr header.i=@c-s.fr header.b=pyjpbDaw; dkim-adsp=pass; dkim-atps=neutral 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 9Y0Ay24P9bpW; Wed, 18 Sep 2019 18:26:08 +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 46YQMh0fTtz9v1BW; Wed, 18 Sep 2019 18:26:08 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1568823968; bh=UgJ2Vcem+ArVILPonqQdgD2fYngRPmGDyA7SB2VX37Y=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=pyjpbDawotebglj/v7nzS+SZ56zwKmvl8UJSMakTVDe9dCV/6GjdddMgM+KIG8OC1 kUNBRNCHr1KKmqumixwnPv1WdKVo4bZRwpWAfR0t7CPiiV7bBbJcoAYH63FALSqftC hwtslTTRJYeOY7/1Aq03nzD37Ir1v6MuTgWj7N0c= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 8FA068B93C; Wed, 18 Sep 2019 18:26:09 +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 WQXgO4akDWdq; Wed, 18 Sep 2019 18:26:09 +0200 (CEST) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id F41388B937; Wed, 18 Sep 2019 18:26:03 +0200 (CEST) Subject: Re: [PATCH V2 2/2] mm/pgtable/debug: Add test validating architecture page table helpers To: Anshuman Khandual , linux-mm@kvack.org Cc: Andrew Morton , Vlastimil Babka , Greg Kroah-Hartman , Thomas Gleixner , Mike Rapoport , Jason Gunthorpe , Dan Williams , Peter Zijlstra , Michal Hocko , Mark Rutland , Mark Brown , Steven Price , Ard Biesheuvel , Masahiro Yamada , Kees Cook , Tetsuo Handa , Matthew Wilcox , Sri Krishna chowdary , Dave Hansen , Russell King - ARM Linux , Michael Ellerman , Paul Mackerras , Martin Schwidefsky , Heiko Carstens , "David S. Miller" , Vineet Gupta , James Hogan , Paul Burton , Ralf Baechle , "Kirill A . Shutemov" , Gerald Schaefer , linux-snps-arc@lists.infradead.org, linux-mips@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org References: <1568268173-31302-1-git-send-email-anshuman.khandual@arm.com> <1568268173-31302-3-git-send-email-anshuman.khandual@arm.com> <502c497a-9bf1-7d2e-95f2-cfebcd9cf1d9@arm.com> <95ed9d92-dd43-4c45-2e52-738aed7f2fb5@c-s.fr> From: Christophe Leroy Message-ID: <64504101-d9dd-f273-02f9-e9a8b178eecc@c-s.fr> Date: Wed, 18 Sep 2019 18:26:03 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Le 18/09/2019 à 07:04, Anshuman Khandual a écrit : > > > On 09/13/2019 03:31 PM, Christophe Leroy wrote: >> >> >> Le 13/09/2019 à 11:02, Anshuman Khandual a écrit : >>> >>>>> +#if !defined(__PAGETABLE_PMD_FOLDED) && !defined(__ARCH_HAS_4LEVEL_HACK) >>>> >>>> #ifdefs have to be avoided as much as possible, see below >>> >>> Yeah but it has been bit difficult to avoid all these $ifdef because of the >>> availability (or lack of it) for all these pgtable helpers in various config >>> combinations on all platforms. >> >> As far as I can see these pgtable helpers should exist everywhere at least via asm-generic/ files. > > But they might not actually do the right thing. > >> >> Can you spot a particular config which fails ? > > Lets consider the following example (after removing the $ifdefs around it) > which though builds successfully but fails to pass the intended test. This > is with arm64 config 4K pages sizes with 39 bits VA space which ends up > with a 3 level page table arrangement. > > static void __init p4d_clear_tests(p4d_t *p4dp) > { > p4d_t p4d = READ_ONCE(*p4dp); My suggestion was not to completely drop the #ifdef but to do like you did in pgd_clear_tests() for instance, ie to add the following test on top of the function: if (mm_pud_folded(mm) || is_defined(__ARCH_HAS_5LEVEL_HACK)) return; > > p4d = __p4d(p4d_val(p4d) | RANDOM_ORVALUE); > WRITE_ONCE(*p4dp, p4d); > p4d_clear(p4dp); > p4d = READ_ONCE(*p4dp); > WARN_ON(!p4d_none(p4d)); > } > > The following test hits an error at WARN_ON(!p4d_none(p4d)) > > [ 16.757333] ------------[ cut here ]------------ > [ 16.758019] WARNING: CPU: 11 PID: 1 at mm/arch_pgtable_test.c:187 arch_pgtable_tests_init+0x24c/0x474 > [ 16.759455] Modules linked in: > [ 16.759952] CPU: 11 PID: 1 Comm: swapper/0 Not tainted 5.3.0-next-20190916-00005-g61c218153bb8-dirty #222 > [ 16.761449] Hardware name: linux,dummy-virt (DT) > [ 16.762185] pstate: 00400005 (nzcv daif +PAN -UAO) > [ 16.762964] pc : arch_pgtable_tests_init+0x24c/0x474 > [ 16.763750] lr : arch_pgtable_tests_init+0x174/0x474 > [ 16.764534] sp : ffffffc011d7bd50 > [ 16.765065] x29: ffffffc011d7bd50 x28: ffffffff1756bac0 > [ 16.765908] x27: ffffff85ddaf3000 x26: 00000000000002e8 > [ 16.766767] x25: ffffffc0111ce000 x24: ffffff85ddaf32e8 > [ 16.767606] x23: ffffff85ddaef278 x22: 00000045cc844000 > [ 16.768445] x21: 000000065daef003 x20: ffffffff17540000 > [ 16.769283] x19: ffffff85ddb60000 x18: 0000000000000014 > [ 16.770122] x17: 00000000980426bb x16: 00000000698594c6 > [ 16.770976] x15: 0000000066e25a88 x14: 0000000000000000 > [ 16.771813] x13: ffffffff17540000 x12: 000000000000000a > [ 16.772651] x11: ffffff85fcfd0a40 x10: 0000000000000001 > [ 16.773488] x9 : 0000000000000008 x8 : ffffffc01143ab26 > [ 16.774336] x7 : 0000000000000000 x6 : 0000000000000000 > [ 16.775180] x5 : 0000000000000000 x4 : 0000000000000000 > [ 16.776018] x3 : ffffffff1756bbe8 x2 : 000000065daeb003 > [ 16.776856] x1 : 000000000065daeb x0 : fffffffffffff000 > [ 16.777693] Call trace: > [ 16.778092] arch_pgtable_tests_init+0x24c/0x474 > [ 16.778843] do_one_initcall+0x74/0x1b0 > [ 16.779458] kernel_init_freeable+0x1cc/0x290 > [ 16.780151] kernel_init+0x10/0x100 > [ 16.780710] ret_from_fork+0x10/0x18 > [ 16.781282] ---[ end trace 042e6c40c0a3b038 ]--- > > On arm64 (4K page size|39 bits VA|3 level page table) > > #elif CONFIG_PGTABLE_LEVELS == 3 /* Applicable here */ > #define __ARCH_USE_5LEVEL_HACK > #include > > Which pulls in > > #include > > which pulls in > > #include > > which defines > > static inline int p4d_none(p4d_t p4d) > { > return 0; > } > > which will invariably trigger WARN_ON(!p4d_none(p4d)). > > Similarly for next test p4d_populate_tests() which will always be > successful because p4d_bad() invariably returns negative. > > static inline int p4d_bad(p4d_t p4d) > { > return 0; > } > > static void __init p4d_populate_tests(struct mm_struct *mm, p4d_t *p4dp, > pud_t *pudp) > { > p4d_t p4d; > > /* > * This entry points to next level page table page. > * Hence this must not qualify as p4d_bad(). > */ > pud_clear(pudp); > p4d_clear(p4dp); > p4d_populate(mm, p4dp, pudp); > p4d = READ_ONCE(*p4dp); > WARN_ON(p4d_bad(p4d)); > } > > We should not run these tests for the above config because they are > not applicable and will invariably produce same result. > >> >>> >>>> >> >> [...] >> >>>>> +#if !defined(__PAGETABLE_PUD_FOLDED) && !defined(__ARCH_HAS_5LEVEL_HACK) >>>> >>>> The same can be done here. >>> >>> IIRC not only the page table helpers but there are data types (pxx_t) which >>> were not present on various configs and these wrappers help prevent build >>> failures. Any ways will try and see if this can be improved further. But >>> meanwhile if you have some suggestions, please do let me know. >> >> pgt_t and pmd_t are everywhere I guess. >> then pud_t and p4d_t have fallbacks in asm-generic files. > > Lets take another example where it fails to compile. On arm64 with 16K > page size, 48 bits VA, 4 level page table arrangement in the following > test, pgd_populate() does not have the required signature. > > static void pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp, p4d_t *p4dp) > { > pgd_t pgd; > > if (mm_p4d_folded(mm)) > return; > > /* > * This entry points to next level page table page. > * Hence this must not qualify as pgd_bad(). > */ > p4d_clear(p4dp); > pgd_clear(pgdp); > pgd_populate(mm, pgdp, p4dp); > pgd = READ_ONCE(*pgdp); > WARN_ON(pgd_bad(pgd)); > } > > mm/arch_pgtable_test.c: In function ‘pgd_populate_tests’: > mm/arch_pgtable_test.c:254:25: error: passing argument 3 of ‘pgd_populate’ from incompatible pointer type [-Werror=incompatible-pointer-types] > pgd_populate(mm, pgdp, p4dp); > ^~~~ > In file included from mm/arch_pgtable_test.c:27:0: > ./arch/arm64/include/asm/pgalloc.h:81:20: note: expected ‘pud_t * {aka struct *}’ but argument is of type ‘pgd_t * {aka struct *}’ > static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgdp, pud_t *pudp) > > The build failure is because p4d_t * maps to pgd_t * but the applicable > (it does not fallback on generic ones) pgd_populate() expects a pud_t *. > > Except for archs which have 5 level page able, pgd_populate() always accepts > lower level page table pointers as the last argument as they dont have that > many levels. > > arch/x86/include/asm/pgalloc.h:static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, p4d_t *p4d) > arch/s390/include/asm/pgalloc.h:static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, p4d_t *p4d) > > But others > > arch/arm64/include/asm/pgalloc.h:static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgdp, pud_t *pudp) > arch/m68k/include/asm/motorola_pgalloc.h:static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmd) > arch/mips/include/asm/pgalloc.h:static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pud_t *pud) > arch/powerpc/include/asm/book3s/64/pgalloc.h:static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pud_t *pud) > > I remember going through all these combinations before arriving at the > current state of #ifdef exclusions. Probably, to solved this all platforms > have to define pxx_populate() helpers assuming they support 5 level page > table. > >> >> So it shouldn't be an issue. Maybe if a couple of arches miss them, the best would be to fix the arches, since that's the purpose of your testsuite isn't it ? > > The run time failures as explained previously is because of the folding which > needs to be protected as they are not even applicable. The compile time > failures are because pxx_populate() signatures are platform specific depending > on how many page table levels they really support. > So IIUC, the compiletime problem is around __ARCH_HAS_5LEVEL_HACK. For all #if !defined(__PAGETABLE_PXX_FOLDED), something equivalent to the following should make the trick. if (mm_pxx_folded()) return; For the __ARCH_HAS_5LEVEL_HACK stuff, I think we should be able to regroup all impacted functions inside a single #ifdef __ARCH_HAS_5LEVEL_HACK Christophe