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 872E0C28EB3 for ; Thu, 6 Jun 2019 18:23:24 +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 6A80220872 for ; Thu, 6 Jun 2019 18:23:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6A80220872 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]:36511 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hYx2p-0006IO-Lf for qemu-devel@archiver.kernel.org; Thu, 06 Jun 2019 14:23:23 -0400 Received: from eggs.gnu.org ([209.51.188.92]:54909) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hYwzu-0003Vq-TI for qemu-devel@nongnu.org; Thu, 06 Jun 2019 14:20:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hYwzt-0000UN-WF for qemu-devel@nongnu.org; Thu, 06 Jun 2019 14:20:22 -0400 Received: from mail-qt1-f178.google.com ([209.85.160.178]:40392) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1hYwzt-0000TS-SY for qemu-devel@nongnu.org; Thu, 06 Jun 2019 14:20:21 -0400 Received: by mail-qt1-f178.google.com with SMTP id a15so3798170qtn.7 for ; Thu, 06 Jun 2019 11:20:21 -0700 (PDT) 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; bh=QyAcNtUFB8xdCi76myNy6Kjfjm014zJkGzxJXNm0UUI=; b=ZJC/gFqOinxzt43AfUwyIe5E0RQLmoEu5jgo+xKrMImy9kmWVrzZV2X4ehuTxTn9tF Q8x97yM5PJvhHPVIqCvVm4+2Kqgtx2QwpyGllbomtg/8xm8lEnYbq3+9hu774TUo/PXV 0pjBEKQ3f0AHH1SeqmWHYJYfenUm+gOQEBN4hQ+QKfjarxvGUQECXIimpmRkml3sNk5g AiNVOt1TDoruAtnchJCAn1PspqCqVn6/2pSek6w8VVRfpAK2/I+GEJ+qsi0edHpk5z2E TO5Un0i1fQBNYmm0SY27izhEFu/OLOtEJC9MXuUTNQ0idhaLWUCsSBtIf34JhWupU315 9u3w== X-Gm-Message-State: APjAAAXw3XBq/eV8C7pXsdpC6NFu5ZjZujS71v4P61syYIKLi6rm+uGd qdGfBGB06SSzG2RsEy7nkMT15Q== X-Google-Smtp-Source: APXvYqzIff5aWeFmd8zK6g1eaqndHFWovb294PDehUIDvpCDiXPc62uo+3qcc2eRwkqim76uSlz0dg== X-Received: by 2002:aed:220e:: with SMTP id n14mr13840148qtc.388.1559845220911; Thu, 06 Jun 2019 11:20:20 -0700 (PDT) Received: from redhat.com (pool-100-0-197-103.bstnma.fios.verizon.net. [100.0.197.103]) by smtp.gmail.com with ESMTPSA id n19sm1066083qkg.58.2019.06.06.11.20.19 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Thu, 06 Jun 2019 11:20:20 -0700 (PDT) Date: Thu, 6 Jun 2019 14:20:18 -0400 From: "Michael S. Tsirkin" To: Kashyap Chamarthy Message-ID: <20190606141904-mutt-send-email-mst@kernel.org> References: <20190606161943.GA9657@paraplu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190606161943.GA9657@paraplu> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.85.160.178 Subject: Re: [Qemu-devel] PCI(e): Documentation "io-reserve" and related properties? 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: 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 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. > -- > /kashyap