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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 29DE1C433FF for ; Fri, 9 Aug 2019 13:58:24 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 2D692214C6 for ; Fri, 9 Aug 2019 13:58:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="DCezGss2" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2D692214C6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 464mzb1z4jzDrC9 for ; Fri, 9 Aug 2019 23:58:19 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=none (mailfrom) smtp.mailfrom=infradead.org (client-ip=2607:7c80:54:e::133; helo=bombadil.infradead.org; envelope-from=willy@infradead.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=infradead.org header.i=@infradead.org header.b="DCezGss2"; dkim-atps=neutral Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 464mrv4hG8zDrBZ for ; Fri, 9 Aug 2019 23:52:31 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=EreDrMASgymCoOwex2lDSh6PBVp8vwwZo8lBW7Dx+AU=; b=DCezGss28UrQwdHuY2bFdI4p4 S1IQudbzVnxD+07DxZGKpMaIkZjBN26Cdg8l2/Fs8GMFEeX1pJqh0qZAiUghQaE6El6M1XDplTDve EJJcjL9sO79CkY0k30aJUEJAymr58OsH+p8EsukYG7F9sRPnn0G8pCmZVLattID9zhXymV5yWXtFQ ciqngFSM0ntk8BRdLo5xQ4zieBSWsCrkihQ+/ft5+CPIVKlVlUX+N97pCSyIU0MATtJ4kwuaN/o18 WCkKlxmfNm5M1Hch5V2lnDpS3brZehU45KR0NW0dNC4+r+Ph0RyNwH7KE6Q/WHvIQU+odBuHV4vuK lstsiJ0Mg==; Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hw5JK-0002PQ-U7; Fri, 09 Aug 2019 13:52:02 +0000 Date: Fri, 9 Aug 2019 06:52:02 -0700 From: Matthew Wilcox To: Anshuman Khandual Subject: Re: [RFC V2 0/1] mm/debug: Add tests for architecture exported page table helpers Message-ID: <20190809135202.GN5482@bombadil.infradead.org> References: <1565335998-22553-1-git-send-email-anshuman.khandual@arm.com> <20190809101632.GM5482@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.4 (2019-03-13) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List 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, 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" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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.