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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 778A9C3A5A1 for ; Mon, 26 Aug 2019 02:37:39 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 446A02168B for ; Mon, 26 Aug 2019 02:37:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="uTLJfy+6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 446A02168B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=gKXa/ObETmwml/ux1dCG7dZLAnWF2S+9VAp2s4ihp0o=; b=uTLJfy+6gjzW5q trQ0xQ3NMRWM1goEz6jVFAjW4zv8X6l8YPA0JxqwqR1zD1G9xWiSynOxIyncL7hmOvoj5dDnFupho 2cCSZRKoW3T/W19iQKho6S/xR5kHmVLwVpDc0V6Si5HUZ+NmknEMYqN5dr6M8CKermj/9TtaY6YGn xz1MIZUDtecZG0G9SHUE/DrhFDJIadv3SW8Vp/35NBr0nifl1KmbG0uTeJND0kuUzmE+AyBQ0uRYK SJoX+czUW4IgmZ8CQCD+Pwm3rlKGgtdwxsB543ikRVmVQRj5XN+K2yqReBfbRzTuctOIsKdQ3t/w8 2/l8fsx3Fw9vPIh3j+XA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i24sp-0005vV-G8; Mon, 26 Aug 2019 02:37:27 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i24sk-0005uq-Pc; Mon, 26 Aug 2019 02:37:24 +0000 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 19249344; Sun, 25 Aug 2019 19:37:20 -0700 (PDT) Received: from [10.162.43.136] (p8cg001049571a15.blr.arm.com [10.162.43.136]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E19513F718; Sun, 25 Aug 2019 19:37:09 -0700 (PDT) Subject: Re: [RFC V2 0/1] mm/debug: Add tests for architecture exported page table helpers To: Matthew Wilcox References: <1565335998-22553-1-git-send-email-anshuman.khandual@arm.com> <20190809101632.GM5482@bombadil.infradead.org> <20190809135202.GN5482@bombadil.infradead.org> From: Anshuman Khandual Message-ID: <7a88f6bb-e8c7-3ac7-2f92-1de752a01f33@arm.com> Date: Mon, 26 Aug 2019 08:07:13 +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: <20190809135202.GN5482@bombadil.infradead.org> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190825_193722_921944_A39E4461 X-CRM114-Status: GOOD ( 16.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , James Hogan , Tetsuo Handa , Heiko Carstens , Michal Hocko , linux-mm@kvack.org, Dave Hansen , Paul Mackerras , sparclinux@vger.kernel.org, Thomas Gleixner , linux-s390@vger.kernel.org, Michael Ellerman , x86@kernel.org, Russell King - ARM Linux , Steven Price , Jason Gunthorpe , linux-arm-kernel@lists.infradead.org, linux-snps-arc@lists.infradead.org, Kees Cook , Masahiro Yamada , Mark Brown , Dan Williams , Vlastimil Babka , Sri Krishna chowdary , Ard Biesheuvel , Greg Kroah-Hartman , linux-mips@vger.kernel.org, Ralf Baechle , linux-kernel@vger.kernel.org, Paul Burton , Mike Rapoport , Vineet Gupta , Martin Schwidefsky , Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 08/09/2019 07:22 PM, Matthew Wilcox wrote: > On Fri, Aug 09, 2019 at 04:05:07PM +0530, Anshuman Khandual wrote: >> On 08/09/2019 03:46 PM, Matthew Wilcox wrote: >>> On Fri, Aug 09, 2019 at 01:03:17PM +0530, Anshuman Khandual wrote: >>>> Should alloc_gigantic_page() be made available as an interface for general >>>> use in the kernel. The test module here uses very similar implementation from >>>> HugeTLB to allocate a PUD aligned memory block. Similar for mm_alloc() which >>>> needs to be exported through a header. >>> >>> Why are you allocating memory at all instead of just using some >>> known-to-exist PFNs like I suggested? >> >> We needed PFN to be PUD aligned for pfn_pud() and PMD aligned for mk_pmd(). >> Now walking the kernel page table for a known symbol like kernel_init() > > I didn't say to walk the kernel page table. I said to call virt_to_pfn() > for a known symbol like kernel_init(). > >> as you had suggested earlier we might encounter page table page entries at PMD >> and PUD which might not be PMD or PUD aligned respectively. It seemed to me >> that alignment requirement is applicable only for mk_pmd() and pfn_pud() >> which create large mappings at those levels but that requirement does not >> exist for page table pages pointing to next level. Is not that correct ? Or >> I am missing something here ? > > Just clear the bottom bits off the PFN until you get a PMD or PUD aligned > PFN. It's really not hard. As Mark pointed out earlier that might end up being just a synthetic PFN which might not even exist on a given system. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel