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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 A6AE8C742A8 for ; Fri, 12 Jul 2019 07:07:56 +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 7B90A208E4 for ; Fri, 12 Jul 2019 07:07:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="HA3E3Amt" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7B90A208E4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au 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:MIME-Version:Message-ID:Date:References :In-Reply-To:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=GoBKWCG+I8kSLoQAm6E1eC+SZiUMMa2ca6NCckOiQqE=; b=HA3E3AmtPCiyD2 CJAQ5lgOIo5innZd9zhYjxqa2Vg6kRKhkFOTyhdpBIxrSVMxSlhB2W1CMi6cfukocIZjATy80OvO+ PESZg1/fRP2iiLmECLlG4EtsAS4sKzf3X9+H3KOKMwMldhlwRfRlulncaCfqn898GMRa1ln1De4fk 0oUvA1zvNqANCJJeOwQfayOb2HmWvBVGGkxN33mLWk+OyvWHTexqirRfJnSD584ABVtPrkNbN2wSC iA2X/6Wtq5OKP9gFMqh0YqEznV9B9Hnb8AyWzeYstjgbXu350lgZ8sFFa3LA6d8NmgRCLWAGdb7Ev O/6xRjK2/zE8yg/QBSDw==; 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 1hlpeu-0004E3-1v; Fri, 12 Jul 2019 07:07:56 +0000 Received: from bilbo.ozlabs.org ([2401:3900:2:1::2] helo=ozlabs.org) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hlpeq-0004D1-Dr for linux-arm-kernel@lists.infradead.org; Fri, 12 Jul 2019 07:07:54 +0000 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 45lPBs30dBz9s00; Fri, 12 Jul 2019 17:07:49 +1000 (AEST) From: Michael Ellerman To: Anshuman Khandual , Andrew Morton Subject: Re: [PATCH V2] mm/ioremap: Probe platform for p4d huge map support In-Reply-To: References: <1561699231-20991-1-git-send-email-anshuman.khandual@arm.com> <20190702160630.25de5558e9fe2d7d845f3472@linux-foundation.org> Date: Fri, 12 Jul 2019 17:07:48 +1000 Message-ID: <87tvbrennf.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190712_000752_686162_9D9D6251 X-CRM114-Status: GOOD ( 10.53 ) 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: Stephen Rothwell , x86@kernel.org, Peter Zijlstra , Catalin Marinas , Dave Hansen , Will Deacon , Michal Hocko , linux-mm@kvack.org, Ingo Molnar , linux-arm-kernel@lists.infradead.org, Andy Lutomirski , Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, "Kirill A . Shutemov" 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 Anshuman Khandual writes: > On 07/03/2019 04:36 AM, Andrew Morton wrote: >> On Fri, 28 Jun 2019 10:50:31 +0530 Anshuman Khandual wrote: >> >>> Finishing up what the commit c2febafc67734a ("mm: convert generic code to >>> 5-level paging") started out while levelling up P4D huge mapping support >>> at par with PUD and PMD. A new arch call back arch_ioremap_p4d_supported() >>> is being added which just maintains status quo (P4D huge map not supported) >>> on x86, arm64 and powerpc. >> >> Does this have any runtime effects? If so, what are they and why? If >> not, what's the actual point? > > It just finishes up what the previous commit c2febafc67734a ("mm: convert > generic code to 5-level paging") left off with respect p4d based huge page > enablement for ioremap. When HAVE_ARCH_HUGE_VMAP is enabled its just a simple > check from the arch about the support, hence runtime effects are minimal. The return value of arch_ioremap_p4d_supported() is stored in the variable ioremap_p4d_capable which is then returned by ioremap_p4d_enabled(). That is used by ioremap_try_huge_p4d() called from ioremap_p4d_range() from ioremap_page_range(). The runtime effect is that it prevents ioremap_page_range() from trying to create huge mappings at the p4d level on arches that don't support it. cheers _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel