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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 67DFEC3A5A2 for ; Tue, 10 Sep 2019 04:45:37 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EA90C21D7B for ; Tue, 10 Sep 2019 04:45:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="gWwFwMGQ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA90C21D7B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-s.fr Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 4433B6B0003; Tue, 10 Sep 2019 00:45:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3F45D6B0006; Tue, 10 Sep 2019 00:45:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2BBD66B0007; Tue, 10 Sep 2019 00:45:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0140.hostedemail.com [216.40.44.140]) by kanga.kvack.org (Postfix) with ESMTP id 0A7026B0003 for ; Tue, 10 Sep 2019 00:45:36 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 8EFFA8243760 for ; Tue, 10 Sep 2019 04:45:35 +0000 (UTC) X-FDA: 75917772630.03.curve51_6ae6b6299c844 X-HE-Tag: curve51_6ae6b6299c844 X-Filterd-Recvd-Size: 14108 Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) by imf10.hostedemail.com (Postfix) with ESMTP for ; Tue, 10 Sep 2019 04:45:34 +0000 (UTC) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 46SCBz6t8WzB09bJ; Tue, 10 Sep 2019 06:45:31 +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=gWwFwMGQ; 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 bU4eAMlI_ySx; Tue, 10 Sep 2019 06:45:31 +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 46SCBz5bQYzB09bF; Tue, 10 Sep 2019 06:45:31 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1568090731; bh=3HdTywXJsBxu7f63a95rihr1tfvWFCcQDr3tUVoe8yw=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=gWwFwMGQhXbQPv4skvhBowgMpQ4CQb9YoCte6J0EYdnWndOz/QIIkIC5h0zvHR3UB Ff9SsJ29XXUzNtVXyrvW+IGqLrX8MaQ1V/dHa+poQ/qL4JRqg1blBogwropiP4BW3n ppQHiwrH0gDyFgNqtIfQfIcOubs7+hioH8IDo+8k= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 7CEF08B78A; Tue, 10 Sep 2019 06:45:32 +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 nnso-4tCA0Zm; Tue, 10 Sep 2019 06:45:32 +0200 (CEST) Received: from pc16032vm.idsi0.si.c-s.fr (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 7E34D8B754; Tue, 10 Sep 2019 06:45:30 +0200 (CEST) Subject: Re: [PATCH 1/1] mm/pgtable/debug: Add test validating architecture page table helpers To: Anshuman Khandual , "Kirill A. Shutemov" Cc: Mark Rutland , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Tetsuo Handa , James Hogan , Heiko Carstens , Michal Hocko , linux-mm@kvack.org, Dave Hansen , Paul Mackerras , sparclinux@vger.kernel.org, Thomas Gleixner , linux-s390@vger.kernel.org, x86@kernel.org, Russell King - ARM Linux , Matthew Wilcox , Steven Price , Jason Gunthorpe , Vlastimil Babka , linux-snps-arc@lists.infradead.org, Kees Cook , Masahiro Yamada , Mark Brown , Dan Williams , Gerald Schaefer , linux-arm-kernel@lists.infradead.org, Sri Krishna chowdary , Ard Biesheuvel , Greg Kroah-Hartman , linux-mips@vger.kernel.org, Ralf Baechle , linux-kernel@vger.kernel.org, Peter Zijlstra , Mike Rapoport , Paul Burton , Vineet Gupta , Martin Schwidefsky , Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" References: <1567497706-8649-1-git-send-email-anshuman.khandual@arm.com> <1567497706-8649-2-git-send-email-anshuman.khandual@arm.com> <20190904221618.1b624a98@thinkpad> <20e3044d-2af5-b27b-7653-cec53bdec941@arm.com> <20190905190629.523bdb87@thinkpad> <3c609e33-afbb-ffaf-481a-6d225a06d1d0@arm.com> <20190906210346.5ecbff01@thinkpad> <3d5de35f-8192-1c75-50a9-03e66e3b8e5c@arm.com> <20190909151344.ghfypjbgxyosjdk3@box> <5883d41a-8299-1584-aa3d-fac89b3d9b5b@arm.com> From: Christophe Leroy Message-ID: <94029d96-47c4-3020-57a8-4e03de1b4fc8@c-s.fr> Date: Tue, 10 Sep 2019 04:45:30 +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: <5883d41a-8299-1584-aa3d-fac89b3d9b5b@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US 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: Archived-At: List-Archive: List-Post: On 09/10/2019 03:56 AM, Anshuman Khandual wrote: > > > On 09/09/2019 08:43 PM, Kirill A. Shutemov wrote: >> On Mon, Sep 09, 2019 at 11:56:50AM +0530, Anshuman Khandual wrote: >>> >>> >>> On 09/07/2019 12:33 AM, Gerald Schaefer wrote: >>>> On Fri, 6 Sep 2019 11:58:59 +0530 >>>> Anshuman Khandual wrote: >>>> >>>>> On 09/05/2019 10:36 PM, Gerald Schaefer wrote: >>>>>> On Thu, 5 Sep 2019 14:48:14 +0530 >>>>>> Anshuman Khandual wrote: >>>>>> >>>>>>>> [...] >>>>>>>>> + >>>>>>>>> +#if !defined(__PAGETABLE_PMD_FOLDED) && !defined(__ARCH_HAS_4LEVEL_HACK) >>>>>>>>> +static void pud_clear_tests(pud_t *pudp) >>>>>>>>> +{ >>>>>>>>> + memset(pudp, RANDOM_NZVALUE, sizeof(pud_t)); >>>>>>>>> + pud_clear(pudp); >>>>>>>>> + WARN_ON(!pud_none(READ_ONCE(*pudp))); >>>>>>>>> +} >>>>>>>> >>>>>>>> For pgd/p4d/pud_clear(), we only clear if the page table level is present >>>>>>>> and not folded. The memset() here overwrites the table type bits, so >>>>>>>> pud_clear() will not clear anything on s390 and the pud_none() check will >>>>>>>> fail. >>>>>>>> Would it be possible to OR a (larger) random value into the table, so that >>>>>>>> the lower 12 bits would be preserved? >>>>>>> >>>>>>> So the suggestion is instead of doing memset() on entry with RANDOM_NZVALUE, >>>>>>> it should OR a large random value preserving lower 12 bits. Hmm, this should >>>>>>> still do the trick for other platforms, they just need non zero value. So on >>>>>>> s390, the lower 12 bits on the page table entry already has valid value while >>>>>>> entering this function which would make sure that pud_clear() really does >>>>>>> clear the entry ? >>>>>> >>>>>> Yes, in theory the table entry on s390 would have the type set in the last >>>>>> 4 bits, so preserving those would be enough. If it does not conflict with >>>>>> others, I would still suggest preserving all 12 bits since those would contain >>>>>> arch-specific flags in general, just to be sure. For s390, the pte/pmd tests >>>>>> would also work with the memset, but for consistency I think the same logic >>>>>> should be used in all pxd_clear_tests. >>>>> >>>>> Makes sense but.. >>>>> >>>>> There is a small challenge with this. Modifying individual bits on a given >>>>> page table entry from generic code like this test case is bit tricky. That >>>>> is because there are not enough helpers to create entries with an absolute >>>>> value. This would have been easier if all the platforms provided functions >>>>> like __pxx() which is not the case now. Otherwise something like this should >>>>> have worked. >>>>> >>>>> >>>>> pud_t pud = READ_ONCE(*pudp); >>>>> pud = __pud(pud_val(pud) | RANDOM_VALUE (keeping lower 12 bits 0)) >>>>> WRITE_ONCE(*pudp, pud); >>>>> >>>>> But __pud() will fail to build in many platforms. >>>> >>>> Hmm, I simply used this on my system to make pud_clear_tests() work, not >>>> sure if it works on all archs: >>>> >>>> pud_val(*pudp) |= RANDOM_NZVALUE; >>> >>> Which compiles on arm64 but then fails on x86 because of the way pmd_val() >>> has been defined there. >> >> Use instead >> >> *pudp = __pud(pud_val(*pudp) | RANDOM_NZVALUE); > > Agreed. > > As I had mentioned before this would have been really the cleanest approach. > >> >> It *should* be more portable. > > Not really, because not all the platforms have __pxx() definitions right now. > Going with these will clearly cause build failures on affected platforms. Lets > examine __pud() for instance. It is defined only on these platforms. > > arch/arm64/include/asm/pgtable-types.h: #define __pud(x) ((pud_t) { (x) } ) > arch/mips/include/asm/pgtable-64.h: #define __pud(x) ((pud_t) { (x) }) > arch/powerpc/include/asm/pgtable-be-types.h: #define __pud(x) ((pud_t) { cpu_to_be64(x) }) > arch/powerpc/include/asm/pgtable-types.h: #define __pud(x) ((pud_t) { (x) }) > arch/s390/include/asm/page.h: #define __pud(x) ((pud_t) { (x) } ) > arch/sparc/include/asm/page_64.h: #define __pud(x) ((pud_t) { (x) } ) > arch/sparc/include/asm/page_64.h: #define __pud(x) (x) > arch/x86/include/asm/pgtable.h: #define __pud(x) native_make_pud(x) You missed: arch/x86/include/asm/paravirt.h:static inline pud_t __pud(pudval_t val) include/asm-generic/pgtable-nop4d-hack.h:#define __pud(x) ((pud_t) { __pgd(x) }) include/asm-generic/pgtable-nopud.h:#define __pud(x) ((pud_t) { __p4d(x) }) > > Similarly for __pmd() > > arch/alpha/include/asm/page.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/arm/include/asm/page-nommu.h: #define __pmd(x) (x) > arch/arm/include/asm/pgtable-2level-types.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/arm/include/asm/pgtable-2level-types.h: #define __pmd(x) (x) > arch/arm/include/asm/pgtable-3level-types.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/arm/include/asm/pgtable-3level-types.h: #define __pmd(x) (x) > arch/arm64/include/asm/pgtable-types.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/m68k/include/asm/page.h: #define __pmd(x) ((pmd_t) { { (x) }, }) > arch/mips/include/asm/pgtable-64.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/nds32/include/asm/page.h: #define __pmd(x) (x) > arch/parisc/include/asm/page.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/parisc/include/asm/page.h: #define __pmd(x) (x) > arch/powerpc/include/asm/pgtable-be-types.h: #define __pmd(x) ((pmd_t) { cpu_to_be64(x) }) > arch/powerpc/include/asm/pgtable-types.h: #define __pmd(x) ((pmd_t) { (x) }) > arch/riscv/include/asm/pgtable-64.h: #define __pmd(x) ((pmd_t) { (x) }) > arch/s390/include/asm/page.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/sh/include/asm/pgtable-3level.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/sparc/include/asm/page_32.h: #define __pmd(x) ((pmd_t) { { (x) }, }) > arch/sparc/include/asm/page_32.h: #define __pmd(x) ((pmd_t) { { (x) }, }) > arch/sparc/include/asm/page_64.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/sparc/include/asm/page_64.h: #define __pmd(x) (x) > arch/um/include/asm/page.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/um/include/asm/page.h: #define __pmd(x) ((pmd_t) { (x) } ) > arch/x86/include/asm/pgtable.h: #define __pmd(x) native_make_pmd(x) You missed: arch/x86/include/asm/paravirt.h:static inline pmd_t __pmd(pmdval_t val) include/asm-generic/page.h:#define __pmd(x) ((pmd_t) { (x) } ) include/asm-generic/pgtable-nopmd.h:#define __pmd(x) ((pmd_t) { __pud(x) } ) > > Similarly for __pgd() > > arch/alpha/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/alpha/include/asm/page.h: #define __pgd(x) (x) > arch/arc/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) }) > arch/arc/include/asm/page.h: #define __pgd(x) (x) > arch/arm/include/asm/pgtable-3level-types.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/arm/include/asm/pgtable-3level-types.h: #define __pgd(x) (x) > arch/arm64/include/asm/pgtable-types.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/csky/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) }) > arch/hexagon/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) }) > arch/m68k/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/mips/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/nds32/include/asm/page.h: #define __pgd(x) (x) > arch/nios2/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) }) > arch/openrisc/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) }) > arch/parisc/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/parisc/include/asm/page.h: #define __pgd(x) (x) > arch/powerpc/include/asm/pgtable-be-types.h: #define __pgd(x) ((pgd_t) { cpu_to_be64(x) }) > arch/powerpc/include/asm/pgtable-types.h: #define __pgd(x) ((pgd_t) { (x) }) > arch/riscv/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) }) > arch/s390/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/sh/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/sparc/include/asm/page_32.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/sparc/include/asm/page_32.h: #define __pgd(x) (x) > arch/sparc/include/asm/page_64.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/sparc/include/asm/page_64.h: #define __pgd(x) (x) > arch/um/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) } ) > arch/unicore32/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) }) > arch/unicore32/include/asm/page.h: #define __pgd(x) (x) > arch/x86/include/asm/pgtable.h: #define __pgd(x) native_make_pgd(x) > arch/xtensa/include/asm/page.h: #define __pgd(x) ((pgd_t) { (x) } ) You missed: arch/x86/include/asm/paravirt.h:static inline pgd_t __pgd(pgdval_t val) include/asm-generic/page.h:#define __pgd(x) ((pgd_t) { (x) } ) > > Similarly for __p4d() > > arch/s390/include/asm/page.h: #define __p4d(x) ((p4d_t) { (x) } ) > arch/x86/include/asm/pgtable.h: #define __p4d(x) native_make_p4d(x) You missed: arch/x86/include/asm/paravirt.h:static inline p4d_t __p4d(p4dval_t val) include/asm-generic/5level-fixup.h:#define __p4d(x) __pgd(x) include/asm-generic/pgtable-nop4d.h:#define __p4d(x) ((p4d_t) { __pgd(x) }) > > The search pattern here has been "#define __pxx(". Unless I am missing something, > I dont see how we can use these without risking build failures. > I guess you missed that arches not defining them fall back on the definitions in include/asm-generic Christophe