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_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 ED136C0044C for ; Wed, 31 Oct 2018 21:16:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A2EDF2080A for ; Wed, 31 Oct 2018 21:16:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=intel-com.20150623.gappssmtp.com header.i=@intel-com.20150623.gappssmtp.com header.b="qCH/a4pL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A2EDF2080A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729702AbeKAGQA (ORCPT ); Thu, 1 Nov 2018 02:16:00 -0400 Received: from mail-ot1-f68.google.com ([209.85.210.68]:37195 "EHLO mail-ot1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726023AbeKAGQA (ORCPT ); Thu, 1 Nov 2018 02:16:00 -0400 Received: by mail-ot1-f68.google.com with SMTP id o14so15951988oth.4 for ; Wed, 31 Oct 2018 14:16:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=jSG1Sq3A1EgvEmarNp8EWlQlPJ4cA9BSdkxAmrib9UY=; b=qCH/a4pL78K+KNeKMviB91GHvMb2yvfyfnzwD7+SEpSFqXpJT+XuU9ZAkZdDi71yn+ blNTnBXpjOoiqFactuaxe+Si/wNk558aFD2KFZ6dyVcZPqIh2tDOmi6LOakGcUEvKcif KpbBzLVamPuiJk23k2/cZyt/jBrv6dHelXITQ9PrvCApV4mDiyugmr7Rrx9mrsz6+bmh XPOECbprQCSuSLEkoTUQeRzkSU8qILPxKuLFY5mweI7RhX+PaoEFNhv5abTQb8f9KxqV jw4Ix2i+69HtMj5mNzgVxUCA9gb+KztBjKSMexefuVPhcYrSXsCtP49y0X19wAKQqbmq resQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=jSG1Sq3A1EgvEmarNp8EWlQlPJ4cA9BSdkxAmrib9UY=; b=gORj0FFHItrekRvVds4hrgOQDZF/6xdZ9eXFHSOlCoW3jXt8CsE7GQX9rUb/GTlYxI wIA7DakTcultrzAlIt2xgitBWW0AqEGKq6IZpR2UDeYVvWQrSYyqPoofDQoWXorLUAOo eXe280RaZBOtVlWpSmfQJxNnRRGQWQQ7hhlZ3I9bYPGTNVlo64hQZBRfEoxWO1D2Oqqt l9xqXiq4iviJG1wOktYZ53LskuDl8Tmb2ggpe6W20VaFmu9fiklLmGFkR0yL8uleiZ8O WqzxDUAUCnq92wAMDSKH0zAp0WJpqnAhO0uDa+g6CCww7tw/LoP9i5o9dPJ89xsPoD6H CyzQ== X-Gm-Message-State: AGRZ1gK842V/uX6AqGw/NTv4lOq43lZ1aizQKAgSwTbeRWn9QOcC9mAW PLgVA73BIF5hU7lRn3TLpa7k+0yXOv1ZQsig1JY5rQ== X-Google-Smtp-Source: AJdET5fh7LtbyAgne/mS+gK4QuqpUoBkKZQAeuOqv3+ZASsDVOH+TPIoPTwp4LmOjkcNSsJsmZkOBU8nEVkZffTC4HY= X-Received: by 2002:a9d:5cc2:: with SMTP id r2mr2549329oti.367.1541020572722; Wed, 31 Oct 2018 14:16:12 -0700 (PDT) MIME-Version: 1.0 References: <20181029210716.212159-1-brho@google.com> In-Reply-To: From: Dan Williams Date: Wed, 31 Oct 2018 14:16:01 -0700 Message-ID: Subject: Re: [RFC PATCH] kvm: Use huge pages for DAX-backed files To: Paolo Bonzini Cc: Barret Rhoden , Dave Jiang , zwisler@kernel.org, Vishal L Verma , rkrcmar@redhat.com, Thomas Gleixner , Ingo Molnar , Borislav Petkov , linux-nvdimm , Linux Kernel Mailing List , "H. Peter Anvin" , X86 ML , KVM list , "Zhang, Yu C" , "Zhang, Yi Z" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 31, 2018 at 1:52 AM Paolo Bonzini wrote: > > On 29/10/2018 23:25, Dan Williams wrote: > > I'm wondering if we're adding an explicit is_zone_device_page() check > > in this path to determine the page mapping size if that can be a > > replacement for the kvm_is_reserved_pfn() check. In other words, the > > goal of fixing up PageReserved() was to preclude the need for DAX-page > > special casing in KVM, but if we already need add some special casing > > for page size determination, might as well bypass the > > kvm_is_reserved_pfn() dependency as well. > > No, please don't. The kvm_is_reserved_pfn() check is for correctness, > the page-size check is for optimization. In theory you could have a > ZONE_DEVICE area that is smaller than 2MB and thus does not use huge pages. To be clear, I was not suggesting that a ZONE_DEVICE check would be sufficient to determine a 2MB page. I was suggesting that given there is a debate about removing the "reserved" designation for dax pages that debate is moot if kvm is going to add interrogation code to figure out the size of dax mappings.