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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 12219CA9EBD for ; Fri, 25 Oct 2019 08:53:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BE3FD21D71 for ; Fri, 25 Oct 2019 08:53:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=c-s.fr header.i=@c-s.fr header.b="JXqe5sri" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BE3FD21D71 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 4BC3D6B0003; Fri, 25 Oct 2019 04:53:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 445426B0006; Fri, 25 Oct 2019 04:53:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 30D766B0007; Fri, 25 Oct 2019 04:53:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0248.hostedemail.com [216.40.44.248]) by kanga.kvack.org (Postfix) with ESMTP id 063786B0003 for ; Fri, 25 Oct 2019 04:52:59 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 7A11A181B048E for ; Fri, 25 Oct 2019 08:52:59 +0000 (UTC) X-FDA: 76081692078.28.fish66_5436c8ee02915 X-HE-Tag: fish66_5436c8ee02915 X-Filterd-Recvd-Size: 6500 Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) by imf06.hostedemail.com (Postfix) with ESMTP for ; Fri, 25 Oct 2019 08:52:58 +0000 (UTC) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 46zyYg6BYkz9vC0w; Fri, 25 Oct 2019 10:52:55 +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=JXqe5sri; 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 6HbhFbyFhM8v; Fri, 25 Oct 2019 10:52:55 +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 46zyYg4vJdz9vC0r; Fri, 25 Oct 2019 10:52:55 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=c-s.fr; s=mail; t=1571993575; bh=4oDjhDK0FsO59rFVGt7Y5o7o8C55+19qgM1BU+899t4=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=JXqe5sriXNQaQXKes3qqbdy43NSrBpwRBpfMpDtkffnR5YWutoOVXs9BVvi7rzrMY QG68soKwprXrLgOAJa7ilqd/FXQFpMspM1kp2DJjaecMsPUGWDU22R2zojRhkImahW aYJ8xO9qWW+5AHxKxjlrTglXwCmCdHn/aPTlV1cw= Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id B9A698B868; Fri, 25 Oct 2019 10:52:56 +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 Z1aZY1cuISIS; Fri, 25 Oct 2019 10:52:56 +0200 (CEST) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 7BC128B895; Fri, 25 Oct 2019 10:52:54 +0200 (CEST) Subject: Re: [PATCH V7] mm/debug: Add tests validating architecture page table helpers To: Anshuman Khandual , Qian Cai Cc: linux-mm@kvack.org, 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 , Mike Kravetz , Ingo Molnar , 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: <69256008-2235-4AF1-A3BA-0146C82CCB93@lca.pw> <3cfec421-4006-4159-ca32-313ff5196ff9@c-s.fr> <763d58b4-f532-0bba-bf2b-71433ac514fb@arm.com> From: Christophe Leroy Message-ID: Date: Fri, 25 Oct 2019 10:52:54 +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: <763d58b4-f532-0bba-bf2b-71433ac514fb@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: quoted-printable 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: Le 25/10/2019 =C3=A0 10:24, Anshuman Khandual a =C3=A9crit=C2=A0: >=20 >=20 > On 10/25/2019 12:41 PM, Christophe Leroy wrote: >> >> >> Le 25/10/2019 =C3=A0 07:52, Qian Cai a =C3=A9crit=C2=A0: >>> >>> >>>> On Oct 24, 2019, at 11:45 PM, Anshuman Khandual wrote: >>>> >>>> Nothing specific. But just tested this with x86 defconfig with relev= ant configs >>>> which are required for this test. Not sure if it involved W=3D1. >>> >>> No, it will not. It needs to run like, >>> >>> make W=3D1 -j 64 2>/tmp/warns >>> >> >> Are we talking about this peace of code ? >> >> +static unsigned long __init get_random_vaddr(void) >> +{ >> +=C2=A0=C2=A0=C2=A0 unsigned long random_vaddr, random_pages, total_us= er_pages; >> + >> +=C2=A0=C2=A0=C2=A0 total_user_pages =3D (TASK_SIZE - FIRST_USER_ADDRE= SS) / PAGE_SIZE; >> + >> +=C2=A0=C2=A0=C2=A0 random_pages =3D get_random_long() % total_user_pa= ges; >> +=C2=A0=C2=A0=C2=A0 random_vaddr =3D FIRST_USER_ADDRESS + random_pages= * PAGE_SIZE; >> + >> +=C2=A0=C2=A0=C2=A0 WARN_ON((random_vaddr > TASK_SIZE) || >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 (random_vaddr < FIRST_USER= _ADDRESS)); >> +=C2=A0=C2=A0=C2=A0 return random_vaddr; >> +} >> + >> >> ramdom_vaddr is unsigned, >> random_pages is unsigned and lower than total_user_pages >> >> So the max value random_vaddr can get is FIRST_USER_ADDRESS + ((TASK_S= IZE - FIRST_USER_ADDRESS - 1) / PAGE_SIZE) * PAGE_SIZE =3D TASK_SIZE - 1 >> And the min value random_vaddr can get is FIRST_USER_ADDRESS (that's w= hen random_pages =3D 0) >=20 > That's right. >=20 >> >> So the WARN_ON() is just unneeded, isn't it ? >=20 > It is just a sanity check on possible vaddr values before it's correspo= nding > page table mappings could be created. If it's worth to drop this in fav= or of > avoiding these unwanted warning messages on x86, will go ahead with it = as it > is not super important. >=20 But you are checking what ? That the compiler does calculation correctly=20 or what ? As mentionned just above, based on the calculation done, what you are=20 testing cannot happen, so I'm having a hard time understanding what kind=20 of sanity check it can be. Can you give an exemple of a situation which could trigger the warning ? Christophe