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,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 E038BC7618B for ; Mon, 29 Jul 2019 08:32:23 +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 B2897206E0 for ; Mon, 29 Jul 2019 08:32:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="U5DxP3VD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B2897206E0 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=ljPjvmXstxt/Mv6GhFMQLAwN73QsK4LJWjAhugPFlQ0=; b=U5DxP3VDc4zYKH t50NINcznNVOgOc6a8JvPEnkGTlfOZ4j1WS+yTMdUXprrOZ15+AgH8cOiDHElUph9CewzcpTY1WyY h0B13sLnul2yDE3rvZsx3Ibk+mcQHX2FTOfUrANyzkDbqUn9ex3OuVI8Io5B+6R25yOdcMT35T7z8 bPqorBKd7S9HVM4aMHAQ4ZjgpyzwBFH5gZqhndyIL3DiIkjmhBm230BG4TMOdmX944tLu1WNdfoLC 1b1Qx7pmcDPND911a9u3a5uTV6RjOmpn82D0mnUflC413BQSPxa/6PhIHA7TvDHrGiE6pfZbWozzD L8jO6OoEiXQpkY47vk5Q==; 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 1hs14x-0004YU-24; Mon, 29 Jul 2019 08:32:23 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hs14r-0004Jl-2h for linux-arm-kernel@lists.infradead.org; Mon, 29 Jul 2019 08:32:19 +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 A9CDF337; Mon, 29 Jul 2019 01:32:15 -0700 (PDT) Received: from [10.162.40.126] (p8cg001049571a15.blr.arm.com [10.162.40.126]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 990293F575; Mon, 29 Jul 2019 01:32:11 -0700 (PDT) Subject: Re: [RFC] mm/pgtable/debug: Add test validating architecture page table helpers To: Matthew Wilcox References: <1564037723-26676-1-git-send-email-anshuman.khandual@arm.com> <1564037723-26676-2-git-send-email-anshuman.khandual@arm.com> <20190725143920.GW363@bombadil.infradead.org> <20190726195457.GI30641@bombadil.infradead.org> From: Anshuman Khandual Message-ID: <10ed1022-a5c0-c80c-c0c9-025bb2307666@arm.com> Date: Mon, 29 Jul 2019 14:02:52 +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: <20190726195457.GI30641@bombadil.infradead.org> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190729_013217_547650_FE80DE26 X-CRM114-Status: GOOD ( 23.10 ) 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 , Kees Cook , Sri Krishna chowdary , Ard Biesheuvel , Masahiro Yamada , Tetsuo Handa , x86@kernel.org, Dave Hansen , linux-kernel@vger.kernel.org, Steven Price , linux-mm@kvack.org, Mark Brown , Andrew Morton , Michal Hocko , linux-arm-kernel@lists.infradead.org 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 07/27/2019 01:24 AM, Matthew Wilcox wrote: > On Fri, Jul 26, 2019 at 10:17:11AM +0530, Anshuman Khandual wrote: >>> But 'page' isn't necessarily PMD-aligned. I don't think we can rely on >>> architectures doing the right thing if asked to make a PMD for a randomly >>> aligned page. >>> >>> How about finding the physical address of something like kernel_init(), >> >> Physical address corresponding to the symbol in the kernel text segment ? > > Yes. We need the address of something that's definitely memory. > The stack might be in vmalloc space. We can't allocate memory from the > allocator that's PUD-aligned. This seems like a reasonable approximation > to something that might work. Okay sure. What is about vmalloc space being PUD aligned and how that is problematic here ? Could you please give some details. Just being curious. > >>> and using the corresponding pte/pmd/pud/p4d/pgd that encompasses that >> >> So I guess this will help us use pte/pmd/pud/p4d/pgd entries from a real and >> present mapping rather then making them up for test purpose. Although we are >> not creating real page tables here just wondering if this could some how >> affect these real mapping in anyway from some accessors. The current proposal >> stays clear from anything real - allocates, evaluates and releases. > > I think that's a mistake. As Russell said, the ARM p*d manipulation > functions expect to operate on tables, not on individual entries > constructed on the stack. Hmm. I assume that it will take care of dual 32 bit entry updates on arm platform through various helper functions as Russel had mentioned earlier. After we create page table with p?d_alloc() functions and pick an entry at each page table level. > > So I think the right thing to do here is allocate an mm, then do the > pgd_alloc / p4d_alloc / pud_alloc / pmd_alloc / pte_alloc() steps giving > you real page tables that you can manipulate. > > Then destroy them, of course. And don't access through them. mm_alloc() seems like a comprehensive helper to allocate and initialize a mm_struct. But could we use mm_init() with 'current' in the driver context or we need to create a dummy task_struct for this purpose. Some initial tests show that p?d_alloc() and p?d_free() at each level with a fixed virtual address gives p?d_t entries required at various page table level to test upon. > >>>> +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD >>>> +static void pud_basic_tests(void) >>> >>> Is this the right ifdef? >> >> IIUC THP at PUD is where the pud_t entries are directly operated upon and the >> corresponding accessors are present only when HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD >> is enabled. Am I missing something here ? > > Maybe I am. I thought we could end up operating on PUDs for kernel mappings, > even without transparent hugepages turned on. In generic MM ? IIUC except ioremap mapping all other PUD handling for kernel virtual range is platform specific. All the helpers used in the function pud_basic_tests() are part of THP and used in mm/huge_memory.c _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel