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_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 43A3CC433E0 for ; Mon, 8 Jun 2020 11:09:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 214C02072F for ; Mon, 8 Jun 2020 11:09:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="MA3pd6T+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729437AbgFHLJL (ORCPT ); Mon, 8 Jun 2020 07:09:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729310AbgFHLJI (ORCPT ); Mon, 8 Jun 2020 07:09:08 -0400 Received: from mail-pg1-x544.google.com (mail-pg1-x544.google.com [IPv6:2607:f8b0:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 22B69C08C5C2 for ; Mon, 8 Jun 2020 04:09:06 -0700 (PDT) Received: by mail-pg1-x544.google.com with SMTP id o8so8589220pgm.7 for ; Mon, 08 Jun 2020 04:09:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=182l15KqndSA3GLGbIwigWBz5qaMbKVubBPH6bU+XdA=; b=MA3pd6T+stPKqP6XIFF5RUOsPh1OVnY6tmlTlRtbD2Y2fTRerrN60aUrzf7wkDjdHw OXaOQEkAzu+AR4bGLEOh0hGO0BN567wfs+0mWAcKNFT1F/9hQpngMTvDFLFvcprFqEOl Z7W3DNh0zdCLk1rlvl0509CDLvqyAoD3P2dWHcK9ADcdZAeyVpGvYdouUaB2wq3hYw23 NV25UHl40C0Blm2jbek0/OUG/at2Tn5OdfPpvbgJwwmWgHF5SI52cZviWhcMFN6Vw0iO qyI6YslneWoVXT2QaTQji/B9AJzpYDSLcZiBw19MosZV22sVBpMwuP9zyFM8rTjFJ/TI ISlA== 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=182l15KqndSA3GLGbIwigWBz5qaMbKVubBPH6bU+XdA=; b=sYo9kuuHnhVHhAf8OXZNLpjpzGpikxrI0ruGBTVhZkQKjV8xnWFeHkvG591KPUhzrg 0NOOUI0TOX/rOzDU1zukzcW/TF0bZ5pdmVX/R06eMHlU8Kh24yHMtVwTbqXY8gecmtvN ry2eBxItYQNIC2iPfG3BUkPiUdviL1iEet7oZc4B4o6qSQtyhxsLYrnddkGdt8JUD3sA b5LNHtgcMuea81XFYz9XAlKKpbliD7ypHtu7dv+DXsaxcli6nRBI3K6PsBl0PJb6FeKZ xp7fduK2CjFWnoqZiICzzW2Cfn/IReyHmJCLIYc0B5XwCfDfcpjrRsff9klI15rxUB2P LdkQ== X-Gm-Message-State: AOAM531SAeG0PlawWOWzpaoLof3gdCc9h9JMifAhqS4sagHA6ZviyuFg tOg+AH2Vm5Rpgp0j3DzOmBA= X-Google-Smtp-Source: ABdhPJzx5s1mT6/uQ0P3CpEcBqAdaBGGuhQQTp6roWUYQ9vKJkrUUJjF4nuxbCmhbgEZPe1u6ZNI7A== X-Received: by 2002:a63:305:: with SMTP id 5mr19162489pgd.74.1591614545531; Mon, 08 Jun 2020 04:09:05 -0700 (PDT) Received: from localhost ([49.207.55.212]) by smtp.gmail.com with ESMTPSA id s21sm3096152pgg.8.2020.06.08.04.09.04 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Mon, 08 Jun 2020 04:09:04 -0700 (PDT) Date: Mon, 8 Jun 2020 16:39:02 +0530 From: afzal mohammed To: Russell King - ARM Linux admin Cc: Arnd Bergmann , Linux ARM , "linux-kernel@vger.kernel.org" Subject: Re: ARM: vmsplit 4g/4g Message-ID: <20200608110902.GA5736@afzalpc> References: <20200512104758.GA12980@afzalpc> <20200514111755.GA4997@afzalpc> <20200514133545.GA5020@afzalpc> <20200516060624.GA6371@afzalpc> <20200607125932.GA4576@afzalpc> <20200607161116.GN1551@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200607161116.GN1551@shell.armlinux.org.uk> User-Agent: Mutt/1.9.3 (2018-01-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, [ my previous mail did not make into linux-arm-kernel mailing list, got a mail saying it has a suspicious header and that it is waiting moderator approval ] On Sun, Jun 07, 2020 at 05:11:16PM +0100, Russell King - ARM Linux admin wrote: > On Sun, Jun 07, 2020 at 06:29:32PM +0530, afzal mohammed wrote: > > get_user_pages_fast() followed by kmap_atomic() & then memcpy() seems > > to work in principle for user copy. > > Have you done any performance evaluation of the changes yet? I think > it would be a good idea to keep that in the picture. If there's any > significant regression, then that will need addressing. Not yet. Yes, i will do the performance evaluation. i am also worried about the impact on performance as these [ get_user_pages() or friends, kmap_atomic() ] are additionally invoked in the copy_{from,to}_user() path now. Note that this was done on a topic branch for user copy. Changes for kernel static mapping to vmalloc has not been merged with these. Also having kernel lowmem w/ a separate asid & switching at kernel entry/exit b/n user & kernel lowmem by changing ttbr0 is yet to be done. Quite a few things remaining to be done to achieve vmsplit 4g/4g Regards afzal