From nobody Tue May 21 21:26:19 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=kevinlocke.name ARC-Seal: i=1; a=rsa-sha256; t=1655859476; cv=none; d=zohomail.com; s=zohoarc; b=QrvEbuhuICbO7MLZ53VAqKV/fdMhxOcaSFtr7Oe2ckH7ZzzpGV39zEiG2eDu6YCT9OOSap/EfCwf8oniFUoFWCX1a52ceDC79nKwaZ3gsPQCdmXyjyugL/PrlkiJlXgf/ZbFtgsMDKF8m3NerJv4RBglslRC+18Ij/h7X12jqGU= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1655859476; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=Wwem9gvImBu/JlSNzr60Adac2+CyLnVbSnNv0WcBFyg=; b=Iizvu+A02Cf87dLP5CjcWyswsllWIa4t1jzf+W7WTE7+BS7+mt5bo7k3SfaO+TPJyzVX1zrICKdbDvIi3T0uTYNDcW9tiB3EiBuvSYfYhvsLJrSYtZB35SPJT3AjMnR1uYyWUKoVLm11KxXCKMb3QB5/lYj0HekaUGFKiq/c27w= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass header.from= (p=none dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 16558594768450.21222363965125624; Tue, 21 Jun 2022 17:57:56 -0700 (PDT) Received: from localhost ([::1]:59038 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1o3ogt-0004yT-Pe for importer@patchew.org; Tue, 21 Jun 2022 20:57:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60382) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1o3ofh-0003d1-4V for qemu-devel@nongnu.org; Tue, 21 Jun 2022 20:56:42 -0400 Received: from vulcan.kevinlocke.name ([107.191.43.88]:41408) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1o3off-00022n-7S for qemu-devel@nongnu.org; Tue, 21 Jun 2022 20:56:40 -0400 Received: from kevinolos.kevinlocke.name (2600-6c67-5000-3d1b-bb03-82a1-4a56-5da8.res6.spectrum.com [IPv6:2600:6c67:5000:3d1b:bb03:82a1:4a56:5da8]) (Authenticated sender: kevin@kevinlocke.name) by vulcan.kevinlocke.name (Postfix) with ESMTPSA id BF0D42F678D7; Wed, 22 Jun 2022 00:56:32 +0000 (UTC) Received: by kevinolos.kevinlocke.name (Postfix, from userid 1000) id DF9471300427; Tue, 21 Jun 2022 18:56:30 -0600 (MDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kevinlocke.name; s=vulcan; t=1655859394; bh=UIX8iZZwUuDImEn3JVa2Iyts2k8M40nF5SuVicc28p0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kpkI/9yQj+A2UGa8fpW9uZaSvWSHoXqPZsvqwVSY01FmVejR3Xw6E7szDVKw+mLbd SWJBDYz9444cHhOtnTrUF40WvsWPAEa3BWW3wDkae8/C12FCQQaSAOsJ7IvkQ3e/vf 8semHcNjndtC1ccUTkBgs3cyRgdrGIrf2bgWLL9c= From: Kevin Locke To: qemu-devel@nongnu.org Cc: Laszlo Ersek , Alex Williamson , Marcel Apfelbaum , Laine Stump , David Gibson Subject: [PATCH v4] docs: mention devices with VBE on Root Complex Date: Tue, 21 Jun 2022 18:56:24 -0600 Message-Id: <8818349ab4a671b9a0f83441e81ed3c26acb93bf.1655859374.git.kevin@kevinlocke.name> X-Mailer: git-send-email 2.35.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=107.191.43.88; envelope-from=kevin@kevinlocke.name; helo=vulcan.kevinlocke.name X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @kevinlocke.name) X-ZM-MESSAGEID: 1655859477925100001 Content-Type: text/plain; charset="utf-8" Mention devices which support VESA BIOS Extensions (VBE) specifically in the list item of the Root Bus section discussing devices placed on the Root Complex. VESA BIOS Extensions (VBE) present a particular challenge not currently noted in the recommendations: ioport access to VBE registers is not forwarded over PCI(e) bridges, even when using the special exception bit for VGA register access.[1] As a result, devices supporting VBE must be placed on the Root Complex for VBE to be usable. The new documentation also clarifies that VBE is used on systems with BIOS firmware, including SeaBIOS, and that it is not generally used on systems with UEFI firmware, including OVMF, where UEFI GOP is used. I say "generally" because VBE may be used on UEFI systems which boot using a Compatibility Support Module (CSM), such as SeaBIOS.[2] This clarification is intended to help users who may not be familiar with VBE to determine whether it is relevant to their situation. [1]: https://mail.coreboot.org/hyperkitty/list/seabios@seabios.org/thread/X= G2RN3HKVRDEDTLA2PRELLIENIIH7II7/#XVP3I2KQVZHSTDA4SNVKOITWGRGSDU3F [2]: https://www.mail-archive.com/edk2-devel@lists.sourceforge.net/msg03788= .html Signed-off-by: Kevin Locke --- Changes since v3: * Rewrite the doc addition, limiting it to VGA devices with VBE, as VBE is the only problematic feature. * Rewrite the commit message as a result of the new scope. * Mention VBE in relation to BIOS and UEFI to help users determine whether they may be using VBE. * Make the doc addition a new paragraph of the first list item, rather than its own list item, since it raises a consideration for PCI graphics devices covered by that list item, rather than a separate class of devices. * Drop Suggested-by: Laszlo Ersek. Since I rewrote the text, I can no longer blame Laszlo for any issues in it. Changes since v2: * Change Signed-off-by to Suggested-by for Laszlo Ersek, as suggested by Laszlo Ersek. Changes since v1: * Replace my overly-broad exception for devices requiring ioport access with a list item specifically for PCI Express devices offering VGA Compatibility provided by Laszlo Ersek. * Rewrite the commit message based on my improved understanding of the issue and the improved scope of the change. docs/pcie.txt | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/docs/pcie.txt b/docs/pcie.txt index 89e3502075..21c2624c44 100644 --- a/docs/pcie.txt +++ b/docs/pcie.txt @@ -48,6 +48,12 @@ Place only the following kinds of devices directly on th= e Root Complex: strangely when PCI Express devices are integrated with the Root Complex. =20 + VGA compatible devices which support VESA BIOS Extensions (VBE) mu= st + be placed on the Root Complex for the VBE registers to be accessib= le, + as the IO port access is not forwarded over bridges or root ports. + VBE may be used on systems with BIOS firmware (e.g. SeaBIOS). It = is + not generally used on systems with UEFI firmware (e.g. OVMF). + (2) PCI Express Root Ports (ioh3420), for starting exclusively PCI Exp= ress hierarchies. =20 --=20 2.35.1