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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 0D028C4321A for ; Tue, 11 Jun 2019 07:22:59 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 D90BC2086D for ; Tue, 11 Jun 2019 07:22:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D90BC2086D 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 ([::1]:52350 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hab7R-0007FQ-Fa for qemu-devel@archiver.kernel.org; Tue, 11 Jun 2019 03:22:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:34885) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hab61-0006Rv-5t for qemu-devel@nongnu.org; Tue, 11 Jun 2019 03:21:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hab60-0000C0-6y for qemu-devel@nongnu.org; Tue, 11 Jun 2019 03:21:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54062) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hab5z-0007zY-RQ for qemu-devel@nongnu.org; Tue, 11 Jun 2019 03:21:28 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AA2E6308218D; Tue, 11 Jun 2019 07:21:05 +0000 (UTC) Received: from paraplu.localdomain (ovpn-117-144.ams2.redhat.com [10.36.117.144]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D28585C541; Tue, 11 Jun 2019 07:21:02 +0000 (UTC) Received: by paraplu.localdomain (Postfix, from userid 1001) id E1CA73E0029; Tue, 11 Jun 2019 09:21:00 +0200 (CEST) Date: Tue, 11 Jun 2019 09:21:00 +0200 From: Kashyap Chamarthy To: "Michael S. Tsirkin" Message-ID: <20190611072100.GM2725@paraplu> References: <20190606161943.GA9657@paraplu> <20190606141904-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190606141904-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Tue, 11 Jun 2019 07:21:05 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] PCI(e): Documentation "io-reserve" and related properties? X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Jun 06, 2019 at 02:20:18PM -0400, Michael S. Tsirkin wrote: > On Thu, Jun 06, 2019 at 06:19:43PM +0200, Kashyap Chamarthy wrote: > > Hi folks, > > > > Today I learnt about some obscure PCIe-related properties, in context of > > the adding PCIe root ports to a guest, namely: > > > > io-reserve > > mem-reserve > > bus-reserve > > pref32-reserve > > pref64-reserve > > > > Unfortunately, the commit[*] that added them provided no documentation > > whatsover. > > > > In my scenario, I was specifically wondering about what does > > "io-reserve" mean, in what context to use it, etc. (But documentation > > about other properties is also welcome.) > > > > Anyone more well-versed in this area care to shed some light? > > > > > > [*] 6755e618d0 (hw/pci: add PCI resource reserve capability to legacy > > PCI bridge, 2018-08-21) > > So normally bios would reserve just enough io space to satisfy all > devices behind a bridge. What if you intend to hotplug more devices? > These properties allow you to ask bios to reserve extra space. Thanks. Would be useful to have them documented in the official QEMU command-line documentation. Otherwise, they will remain as arcane properties that barely anyone knows about. -- /kashyap