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=-2.2 required=3.0 tests=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 D8504CA9EBE for ; Fri, 25 Oct 2019 08:24:00 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A465721872 for ; Fri, 25 Oct 2019 08:24:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A465721872 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 28ABD6B0007; Fri, 25 Oct 2019 04:24:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 260196B0008; Fri, 25 Oct 2019 04:24:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 19FE26B000A; Fri, 25 Oct 2019 04:24:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0083.hostedemail.com [216.40.44.83]) by kanga.kvack.org (Postfix) with ESMTP id ED2716B0007 for ; Fri, 25 Oct 2019 04:23:59 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 7B6AC8249980 for ; Fri, 25 Oct 2019 08:23:59 +0000 (UTC) X-FDA: 76081618998.16.seat62_7a1787ba9384d X-HE-Tag: seat62_7a1787ba9384d X-Filterd-Recvd-Size: 4685 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf44.hostedemail.com (Postfix) with ESMTP for ; Fri, 25 Oct 2019 08:23:58 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DF61228; Fri, 25 Oct 2019 01:23:57 -0700 (PDT) Received: from [10.162.41.137] (p8cg001049571a15.blr.arm.com [10.162.41.137]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8D6FC3F718; Fri, 25 Oct 2019 01:23:44 -0700 (PDT) Subject: Re: [PATCH V7] mm/debug: Add tests validating architecture page table helpers To: Christophe Leroy , 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> From: Anshuman Khandual Message-ID: <763d58b4-f532-0bba-bf2b-71433ac514fb@arm.com> Date: Fri, 25 Oct 2019 13:54:14 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <3cfec421-4006-4159-ca32-313ff5196ff9@c-s.fr> Content-Type: text/plain; charset=utf-8 Content-Language: en-US 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: On 10/25/2019 12:41 PM, Christophe Leroy wrote: >=20 >=20 > 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 releva= nt 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 >> >=20 > Are we talking about this peace of code ? >=20 > +static unsigned long __init get_random_vaddr(void) > +{ > +=C2=A0=C2=A0=C2=A0 unsigned long random_vaddr, random_pages, total_use= r_pages; > + > +=C2=A0=C2=A0=C2=A0 total_user_pages =3D (TASK_SIZE - FIRST_USER_ADDRES= S) / PAGE_SIZE; > + > +=C2=A0=C2=A0=C2=A0 random_pages =3D get_random_long() % total_user_pag= es; > +=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; > +} > + >=20 > ramdom_vaddr is unsigned, > random_pages is unsigned and lower than total_user_pages >=20 > So the max value random_vaddr can get is FIRST_USER_ADDRESS + ((TASK_SI= ZE - 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 wh= en random_pages =3D 0) That's right. >=20 > So the WARN_ON() is just unneeded, isn't it ? It is just a sanity check on possible vaddr values before it's correspond= ing page table mappings could be created. If it's worth to drop this in favor= of avoiding these unwanted warning messages on x86, will go ahead with it as= it is not super important. >=20 > Christophe >=20