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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,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 6D032C04AB6 for ; Wed, 29 May 2019 01:22:18 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 40D9C2070D for ; Wed, 29 May 2019 01:22:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 40D9C2070D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:45251 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVnIH-0001Ob-B6 for qemu-devel@archiver.kernel.org; Tue, 28 May 2019 21:22:17 -0400 Received: from eggs.gnu.org ([209.51.188.92]:47686) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVnHY-00016p-Rk for qemu-devel@nongnu.org; Tue, 28 May 2019 21:21:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hVnHX-0001Xe-1H for qemu-devel@nongnu.org; Tue, 28 May 2019 21:21:32 -0400 Received: from mail-wm1-f65.google.com ([209.85.128.65]:40167) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1hVnHS-0001S1-5J for qemu-devel@nongnu.org; Tue, 28 May 2019 21:21:28 -0400 Received: by mail-wm1-f65.google.com with SMTP id 15so359312wmg.5 for ; Tue, 28 May 2019 18:21:19 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=ycYOtGiWthinXl/Acj8a7yeW0iGtvdSx5stpHQ0pLsk=; b=g2urJD0uiBBLxtfj97r3VOZTkvy5yHdF8hByvnQQe996F0DXJBg3fsJI68Er+pIkIM dEIEQpp+UfnUWhEF4BjsREjmluEVboCiMtMD89Oh9u77GDwOld32F6+3oHXvK6R/bGJE DWVGyvy5cBlMaxeSAvtjZE7lUFXkaoZ3DT3GHiqTcze+Gy3E/V45lyENnEDc8CUsGXfg rsxh+s4jr9N90g9vAtx6tbknK9IthjlY9WVknDWo/GMLslMJnZBIj8EZnhrIb+oHl/OL Gu8Z63t5g/HKRlyE8vlwtdYptnKGSX+4F7VdCvXoIcSheNv+ToVDmsFRW+ULLm/FwUGG pFKw== X-Gm-Message-State: APjAAAWmgW7MXOZY7EAIo+EA65h4a3hMwOTXLZdbFu3OdqwMJV61CImc ChFR5fJYRmNPXdErsFHlQ/QRYw== X-Google-Smtp-Source: APXvYqwzL8tm/m5Os0a/FasPn2DjbMILphwdxDuTsMvVG3iX5GScFGcVa/5u90NmQuX0n2aicBUsPg== X-Received: by 2002:a1c:7c07:: with SMTP id x7mr4595427wmc.60.1559092878354; Tue, 28 May 2019 18:21:18 -0700 (PDT) Received: from [192.168.10.150] ([93.56.166.5]) by smtp.gmail.com with ESMTPSA id z5sm4216771wma.36.2019.05.28.18.21.17 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 28 May 2019 18:21:17 -0700 (PDT) To: Gerd Hoffmann , qemu-devel@nongnu.org References: <20190528204838.21568-1-kraxel@redhat.com> From: Paolo Bonzini Message-ID: Date: Wed, 29 May 2019 03:21:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190528204838.21568-1-kraxel@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.85.128.65 Subject: Re: [Qemu-devel] [PATCH] q35: split memory at 2G X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Richard Henderson , =?UTF-8?B?TMOhc3psw7Mgw4lyc2Vr?= , Eduardo Habkost , "Michael S. Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 28/05/19 22:48, Gerd Hoffmann wrote: > Original q35 behavior was to split memory 2.75 GB, leaving space for the > mmconfig bar at 0xb000000 and pci I/O window starting at 0xc0000000. > > Note: Those machine types have been removed from the qemu codebase > meanwhile because they could not be live-migrated so there was little > value in keeping them around. > > With the effort to allow for gigabyte-alignment of guest memory that > behavior was changed: The split was moved to 2G, but only in case the > memory didn't fit below 2.75 GB. > > So today the address space between 2G and 2,75G is not used for guest > memory in typical use cases, where the guest memory sized at a power of > two or a gigabyte number. But if you configure your guest with some odd > amout of memory (such as 2.5G) the address space is used. Wasn't it done to ensure pre-PAE OSes could use as much memory as possible? (If you run pre-PAE OSes with more RAM than can fit below 4G, you can just reduce the amount of memory and get all the 2.75G). Paolo