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=-3.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=ham 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 4CBCAC43381 for ; Thu, 21 Feb 2019 21:06:29 +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 060CB2080F for ; Thu, 21 Feb 2019 21:06:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="mblATrPL"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="NKPNMRo3" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 060CB2080F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=shutemov.name 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:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=5/xy5gtlu0ElBO46hy+PQtjoPvN4dJvcqDKzOTKCjKY=; b=mblATrPL7Q2YAX KlYs6XUcuN7KbI8DFkF0Q9B4CS3hFw9i1relYNU+V3mqsPC6GL+lUxiEo98nU/zBM+2U3Tr2j4zPa SYo7nyb/DXqqJ//suOnuwMTeJRFtf1msz52Q0RjCz1vlRT85LPXhZTF72rPQFLt5mp50OKCuIUalm 5XeQhFWKOAEmn1GIValXXg+2HiSVhRfGBgxo1BZpnyXWuV1VyrUX8G0gp1tNrJbS+cpAqCDmhRmZH 5pJ6QZxnf70b/PN1h46eyy+Qdegw+JWWTenvsgH4i17AydMjuPj6gv6eV53CFBm3MrtfhG7ujZ96t luyeh3qZ/fcp7DdtQqHg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gwvY3-00045W-1c; Thu, 21 Feb 2019 21:06:27 +0000 Received: from mail-lf1-x143.google.com ([2a00:1450:4864:20::143]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gwvXz-000451-N6 for linux-arm-kernel@lists.infradead.org; Thu, 21 Feb 2019 21:06:25 +0000 Received: by mail-lf1-x143.google.com with SMTP id e27so7484lfj.8 for ; Thu, 21 Feb 2019 13:06:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=VaJWYAuyQeiGU3BWEwsARtgeEZnMSVA9riqh9x2CWpM=; b=NKPNMRo3ErcDG4ky/fPBEzQnksX3jp49gQoP5BNMEml3Xa4+q8OBDs7eAYPRL6qIaa YnxzxJBtMWzo0qktAuwG5l6TasJiZlpxVYcujUQeC9ZyBOy31eoJP2BEWav5d6MVOWFT ih1drWY0aq4VUyqJizrEh6aOe04fRSqfb/3/vv8pOVYQ7XigqKstevSLa4l2aF42wYPT KkNfHtJMkZH4omVe/xjOwvs0Oo/DxPn8TwLXZrI3EbTeppnTN0jFJG0j/9bVHyOeAA6v LYgZf4FpipElkeU0YNCJqUuOwJL3/b6ZeZT+gWOK+CkI4MM2RS0pxYuSWRnBJkwbSBGq etsw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=VaJWYAuyQeiGU3BWEwsARtgeEZnMSVA9riqh9x2CWpM=; b=Opt5pdtf1rh96NGR1w+hPSXWIKiTzwdnhaCJcWgpxeauXUXHejhiEqncf0AQrZFw2B fYUcai+nitxIwCWeXjxJzcriNTZSN5Gmz/EO9zohXjHcU5Hoump/SbDRTKGFhnQsLwHD 5z+PJFemCEcG/4oNsidtkd4taO0tiuM9vP4lQ7uGXTGjn4VQLqJSAWvuV3SJdmpfH7mA d77YRjEnkuha7k59nFuXQ7EnT1X5irdeL2tUv8uASomxguPYcN99OQ3BMITr2/BUgrbn pDYcWLSPtVPSVBOdlTcSIaonrBwnpQLReEd5eO8ERnsDKybbvzaSd2yVvEIKRbaHSNiq psPw== X-Gm-Message-State: AHQUAubrS7qSYmz0WkBIoZ0hUFzsmHDXzS/RFKEzQL948lfXR+ww7pWX yUT18TbNmoE2VO5slVsf1kObzA== X-Google-Smtp-Source: AHgI3IZPyEOrLA7QJzleHCFDOD1gvwBgGn5TGNiVcau/7k1voltB6KSCgJi+MGXiUxUSeuln6x/iYw== X-Received: by 2002:a19:6001:: with SMTP id u1mr317237lfb.56.1550783181385; Thu, 21 Feb 2019 13:06:21 -0800 (PST) Received: from kshutemo-mobl1.localdomain (mm-23-232-121-178.mgts.dynamic.pppoe.byfly.by. [178.121.232.23]) by smtp.gmail.com with ESMTPSA id z85sm6143768lff.80.2019.02.21.13.06.20 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 21 Feb 2019 13:06:20 -0800 (PST) Received: by kshutemo-mobl1.localdomain (Postfix, from userid 1000) id E14B7301708; Fri, 22 Feb 2019 00:06:18 +0300 (+03) Date: Fri, 22 Feb 2019 00:06:18 +0300 From: "Kirill A. Shutemov" To: Steven Price Subject: Re: [PATCH v2 03/13] mm: Add generic p?d_large() macros Message-ID: <20190221210618.voyfs5cnafpvgedh@kshutemo-mobl1> References: <20190221113502.54153-1-steven.price@arm.com> <20190221113502.54153-4-steven.price@arm.com> <20190221142812.oa53lfnnfmsuh6ys@kshutemo-mobl1> <20190221145706.zqwfdoyiirn3lc7y@kshutemo-mobl1> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190221_130623_803702_3FE90D9E X-CRM114-Status: GOOD ( 15.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , x86@kernel.org, Arnd Bergmann , Ard Biesheuvel , Peter Zijlstra , Catalin Marinas , Dave Hansen , Will Deacon , linux-kernel@vger.kernel.org, linux-mm@kvack.org, =?utf-8?B?SsOpcsO0bWU=?= Glisse , Ingo Molnar , Borislav Petkov , Andy Lutomirski , "H. Peter Anvin" , James Morse , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, "Liang, Kan" 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 Thu, Feb 21, 2019 at 05:16:46PM +0000, Steven Price wrote: > >> Note that in terms of the new page walking code, these new defines are > >> only used when walking a page table without a VMA (which isn't currently > >> done), so architectures which don't use p?d_large currently will work > >> fine with the generic versions. They only need to provide meaningful > >> definitions when switching to use the walk-without-a-VMA functionality. > > > > How other architectures would know that they need to provide the helpers > > to get walk-without-a-VMA functionality? This looks very fragile to me. > > Yes, you've got a good point there. This would apply to the p?d_large > macros as well - any arch which (inadvertently) uses the generic version > is likely to be fragile/broken. > > I think probably the best option here is to scrap the generic versions > altogether and simply introduce a ARCH_HAS_PXD_LARGE config option which > would enable the new functionality to those arches that opt-in. Do you > think this would be less fragile? These helpers are useful beyond pagewalker. Can we actually do some grinding and make *all* archs to provide correct helpers? Yes, it's tedious, but not that bad. I think we could provide generic helpers for folded levels in and rest has to be provided by the arch. Architectures that support only 2 level paging would need to provide pgd_large(), with 3 -- pmd_large() and so on. -- Kirill A. Shutemov _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel